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Volume 26 No 3 May/June 1999 Journal Australian Water & Wast ewater Association

Editorial Board F R Bishop, Chairman B N Anderson, D Deere, P Draayers, W J Dulfer, G Fmlayson, GA Holder, P Johnstone, M Kirk, P Nadebaum, N Orr, J D Parker, M Pascoe, A J Priestley,] Rissman, F Roddick, EA Swinton

·, Water is a refereed journal. This symbol indicates that a paper has been refereed.

General Editor Margaret Metz, email: mmetz@awwa.asn.au AWWA Feder,il Office (see postal address below)

CONTENTS From the Federal President ... ......... .. ....... ... .. ..................... ....... .. ................... 2 From the Executive Director .... ...... .............................. .. ................... ............. 4

Features Editor EA (Bob) Swinton 4 Pleasant View Cres, Wheelers Hill Vic 3150 Tel/ Fax (03) 9560 4752 Email: swintonb@c031.aone.net.au

MY

Northern Territory - Mike Lawton Tel (08) 8924 6411 Fax (08) 8924 6410

Queensland - Tom Belgrave T e l (07) 3810 7967 Fax (07) 3810 7964

South Australia - Angela Colliver T e l (08) 8227 1111 Fax (08) 8227 I 100

Tasmania - Ed K.leywegt Tel (03) 6238 2841 Fax (036) 234 7 I 09

Victoria - Mike Muntisov Tel (03) 9278 2200 Fax (03) 9600 1300 Western Australia - Jane Oliver Tel (08) 9380 7454 Fax (08) 9388 1908

Advertising & Administration

OF

VIEW

Every Drop Counts ........................................................................................... 3

R Welford

Branch Correspondents ACT - Ian Bergman Tel (02) 6230 1039 Fax (02) 6230 6265 New South Wales - Leonie Hu.xedurp Tel (02) 9895 5927 Fax (02) 9895 5967

POINT

CATCHMENT HYDROLOGY Cooperative Research Centre for Catchment Hydrology Special Feature ..... 7 Meeting Industry Needs ... ... ......... ... ....................... .. .. ..................... ... ........... .. 8

RMein Let's Get the Hydrological Facts Straight! ......... ...... .. .. .. ...... .. ... .... .. ............. 9

J Langford Sources of Sediment and Phosphorus in Tarago Reservoir .............. ...... 11

F J Dye r, J M Olley, G A Moore, AS Murray Trees on HIiis: Better Growth = Less Waterlogglng ............ ........... .. .. ....... 13 RP Silberstein, D L M cj annet, R. A Vertessy AQUACYCLE: An Urban Water Reuse Computer Model ............................. 17 G Mitchell, R. Mein, T McMahon Reducing Salt Exports from an Irrigated Catchment at Barr Creek, Victoria ............ .... ...................................................................... 21

AWW A Federal Office

M Gilfedder

PO Box 388, Artarmon NSW 1570

Using Radar to Predict Floods ..................... .. ........ ...................................... 25

Level 2, 44 Hampden Road, Artarmon Tel (02) 9413 1288 Fax (02) 9413 1047 Email: info@awwa.asn.au Advertising: Angela Makris Graphic Design: Elizabeth Soo (formerly Wan)

Water (ISSN 0310 - 0367) is published six times per year: January, March, May,July, September, November by

Australian Water & Wastewater Association Inc ARBN 054 253 066

AW Seed , P Jordan, X Su n, R Srikanthan, J Elliott Trees for Profit and a Healthy Watertable? ........ .... ................. .................. 28 RP Silberstein, R. A Vertessy,J Morris, PM Feikema Technology Transfer: Satisfying the Thirst for Better Tools and Knowledge ..... ... .... ............. .. ................. .................................................. 32

D Pe rry WATER ·, Dissolved Organic Matter in Reservoirs: A Review .. .... ......................... 35

KM Spark

Federal President

WASTEWATER

Greg Cawston

Executive Director Chris Davis Au stralian Water & Wastewater Association (A WW A) assumes no responsibility for opinions or statements of facts expressed by contribmors or advertisers. Editorials do not necessarily represen t official A WW A policy. Ad vertisements are included as an information service to readers and are reviewed before publication to ensure relevance to the water en vironment and objectives of AWW A. All material in Water is copyright and should not be reproduced wholly or in part without the written permjssion of the General Editor.

Subscriptions Water is sent to all members of AWW A as one of the privileges of membership. Non-members can obtain Water on subscription at an annual subscription rate of$50 (surface mail).

Visit the Australian Water & Wastewater Association I HOME PAGE 1 and 11C0111 our calendar, bookshop, membarahlp forms and_!() P81118 of Information at

.

·, Effluent Irrigation in Queensland: Modelling Sustainable Loading Rates .. 39

X Hu ENVIRONMENT Outcome-focused ... Draft Environmental Water Quality Guidelines .......... 43

E A (Bob) Swinton BUSINESS Water and the GST ..................................... ... ....... ................ .. .. .... .. ............... 46

D Kuhne DEPARTMENTS From the Top of the Well ........ ............. ......... .. ........................................... .... 4 International Aff Ill ates ...... ..... .. ......................... ..... .. .. .. ... .. ............................ 5 Books ............................ ..................... ..... ...... ... .......... ........ ......... ........ 38, 41, 42 Meetings ... ...... .. ... .. ... .... ... ... ....... ... .... ...... ...... ... ................... ........................... 48 OUR COVER : The CRC for Catchment H ydrology has a vision of the sustain-

able management of the nation's water resources through an integrated approach to landuse, water allocation, hydrologic risk and environmental values (see C R C fea ture this issue). Photo of Tasmanian stream above Lake Vera courtesy of Peter Hairsine, CSIRO Land and Water


FROM

THE

PRESIDENT

Would You Buy Secondhand Water? A looming issue all around Australia is that of facing up to the immutable water cycle. Used water has to go somewh ere and inevitably some of the wa ter we u se has been used before. The head-in-the- sand attitude is to pretend this d oes not h appen, that water discha rged into a river and then withdrawn downstream has somehow miraculously lost its taint and that it is good for use. In many respects, perceptions rather than science rule in this situation. The politically correct view is that putting used water into any waterbody is bad, but 'reuse' is good and must be enforced as widely as possible, even when real environmental o utcomes may be negative and the so-called reuse makes no econo1nic sense. On the other hand, several protagonists see a limited role for reuse, b ecause they are co n cerned about h ealth risks. The community at large may fall into this ca tegory, because people simply don't understand the issu es, processes and risks. H ealth regulators in general and a slice of the water practitioner group falls into this category too. If supplying wate r to p eople means picking the best possible source, using sewage as a starting point is simply anathema. This creates serious dilemmas fo r people w h o have to implement water cycle management. They are operating in an environment w h ere there are unrealistic expectations as to how much

water could be reused and seve re constraints on how it can be used. Both the community and the environment are going to pay dearly unless these inconsistencies can be removed. As far as a solid, analytical appreciation is concerned, the current CSIRO Urban Water Cycle Program should soon begin to produce some mathematical models to predict just how effective water reu se can be. Pioneering work being done in many communities will also help, some of it funded und er the Na tural H e ritage Trust Fund. T hat will p rovide practical demonstrations fo r us to learn from. Great strides of understanding are needed , though, among community members, regulators and designers about how the ri sks associated with

water reuse can be compared with other daily risks in life . Insistence o n a zero ri sk approach is co unter-produ ctive, because it implies that it is irresponsible to even consider potable reu se. The application of rational risk analysis and management strategies will, I believe, ill ustrate th at potable reuse of effluent is practically ac hievable and help to weigh up the costs and benefits. Recent moves at the national level to exa mine this question dispassionately are therefore most welcome and should be encouraged . Water reuse is too big an issue to be either slipped in surreptitiously or ignored. Vigorous and ope n airing by all stakeholders is the only way it can be thrashed out to the p oint w here everyone can comprehend all the ramifications-to the environme nt, health and the economy . Au stralia's variable climate and fragile waterways demand flexibility and pragmatism from th eir custodians. It is also important to acknowledge tha t direct potable reuse is one extrem e on a con tinuum fro m no reuse (patently unrealistic) to complete reu se. Risk management studies w ill illuminate just where we should be on the spectrum for eac h situation . An informed com munity will be ready to listen to th e facts and support rational decisions. W e need a national, collaborative effort to ensure that the necessary information is delivered, impartialJy and widely, to all age groups. Greg Cawston

Tap Into A Vital Resource Become a member of the Australian Water and Wastewater Association Dr/ Ms/Mr First name ................................................................................................................ Last name ........ ......... ........... .................. ....... ... Position .. Organisation .......................... .................................................................................................... . Postal address ........................................................................................... ................... .............. . ... ..... .... .... .... ..... .... .... ......... .... ......... .... .... .... ........ State

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WATER M AY/JUN E 1999

Date

.J

Email: info@awwa.asn.au Internet: http://www.awwa.asn.au


MY

POINT OF VIEW

Every Drop Counts R Welford Rod Welford Is the Queensland Minister for Environment and Heritage and Natural Resources.

Over the past few decades many Australians have forgo tten that we live on one of the driest contine nts on Earth. W hether we like it or not, many aspects of our lives are dictated by water in some form or other. The majority of our rapidly growing population is crammed into a narrow coastal strip where there is access to safe, clean dri nking water. Similarly, ou r rural industries have developed in close proximity to rivers. Recently, debate has intensified over the way in which we dispose of o ur effluent and wastewater. The drinking wa ter sca re in Sydney last year made peop le m uch more aware of water qu ality issues. In Queensland, good management over many years by local governments has e nabled the sta te to become Au stralia's most decentralised. O u r population 1s spread over many thousands of kilometres. Even the most conservative population estimates suggest Queensland will grow markedly over the next 50 years. Sou t h-east Queensland will pass Melbou rne as Australia's second largest metropolitan area in a few years. T his places press ure on us all to maintain liveability-to make sure air, wa ter and noise fi t properly into the eq u ation. If we are to maintain and improve our quality oflife , we wi ll have to manage our resou rces wisely. Over the past 30 years in Q ueensland the re has been a concentrati on on development of new water infrastructu re-dams, weirs and storage facil ities-to cope with the commu nity's growing water needs, wi thout putting the same effort into ways to u se water more efficiently. The Queensland Labor Government is attempting to persuade the com munity, particularly ru ral industry, that ecologically sustainable developm ent is a smart lo ng- term strategy. We cann ot co n tinu e looking at our resources with short-term views. Va rious studies have demonst rated the irreparable damage caused to o ur environmen t by E uropean settlement in Australia. M uch of this development was carried ou t withou t understanding the long- term imp acts. It is quite natural that many rural

produ cers worry about their short-term fu ture, thei r incomes, their families and their fut ure. Many hear the noises emanating from Gove rnme nt abo ut water conservation an d fear th e worst. Since coming to office, the Beattie Government has progressed a new co n cept to sustain our wa terways w ith the WAMP, or Water Al location Managem ent Plan process. The state's fi rst W AMP will be completed fo r the Fitzroy Basin. A draft plan was completed in September th is year and released for public consultation. A number o f key stakeh olders , in clu ding the Queensland Fa rmers Federation , sough t additional time to comment o n the plan. The Government agreed to extend th e time for consultatio n , taking the view that it was more im portant to get it right than to rush . The aim is a workable plan t hat creates a framework for the sustai nable use of the region's waterways. We want to balance agricultural, industrial and domestic water uses with the environmental needs of the catchment. It is a complex equation and in this particular case it is com plicated by the pre-existing assumption that a new dam should be built on the Dawson River. Avid poli tical watchers would have noticed the Nathan Dam has gene rated much comment from the same quarters as those who are keen to build withou t regard to what proper planning studies might suggest. While the W AMP process is an important platform upon which we can start to sustain our waterways, so too is better use of our existing water resources. The Government is e n couraging indu stry an d local government to

examine closely the more efficient use of water and the reuse of wastewater. A proposal co ncerning the piping of Brisbane's wastewater to the Lockyer Valley and Da rling Downs for irrigation has attracted considerable media attention over the past 12 months. I am awaiting a report on the feasi bility of such a proj ect. Further n orth , the Mackay City Cou ncil is about to commence a feasibility study for reu se of effluent from the Mt Bassett and B ucasia Sewerage Treatment Plants for irrigation of cane. Another important cu rrent project is the Q ueensland Wastewater Reuse Strategy. T his proj ect aims to produce a w ho le-of-government strategy covering all areas of water reclamation. I believe we have only scratched the su rface of the enormous potential fo r better management and efficiency of water use and water recycli ng strategies. T here is a need fo r thorough community understanding of water and wastewater issues. Com munity education and awareness will be a critical part of this process. The Queenslan d Governme n t is working with the rural sector, industry and local government to i ntroduce wa te r efficiency initia tives in both urban and rural environments. T hese measu res are p art of a longterm strategy. Naturally, there will be teethi ng problems as various industry sectors adjust to a new vision of the fu ture. Every Queenslander can benefit fro m better use of water because, over time, it mea ns governments may be able to delay or even elim.inate expensive water solutions. Funds can be made available for other essential public services. At present, the pressu re o n our waterways is intense. Many catchments are badly degraded fro m years of overuse and or neglect. A record number of fis h kills in Queensland during 1998 highlighted water quality issues. T he strategies I have discussed in this article o u tline, in broad terms, the Government's ou tlook for the future. Wi th our state's ideal climate, more and more people want to eajoy the lifestyle Q ueensland offers. T his means we have to sustain and ma nage ou r resources, particularly water, in a way that guarantees we can main tain and im prove quali ty of life for generations to come. WATER M AY/ JUNE 1999

3


FROM THE EXECUTIVE DIRECTOR

What's In A Name? Our Association has proudly borne its present name since its inception. But times change, and so do associations. When AWWA was established 37 years ago, the agenda driving its founding members was that of building the much needed infrastructure to provide adequate water supplies and sewerage for our major cities. The old-fashioned wo rd 'sewage' was replaced by the more modern (and euphemistic) term 'wastewater.' T hus the name, 'Australian Water and Wastewater Association' was a good one for the early Association. As the first multi-disciplinary association to address itself entirely to water issues, AWW A provided valua ble professional development and networking opportunities for its members and the communities that relied on them. By the mid 1980s much of the necessary infrastructure had been built and some acute sanitation problems had been solved for cities. At the same time, practitioners who had previously operated in separate boxes (labelled stormwater, water supply o r wastewater) began to find that they could not operate independently of one another. A major strategic planning exercise threw up the need for AWWA to play a broader role in the water cycle, and for membership to be more freely available to anyone with an interest in water. It was abou t this time that our first Executive Director, Peter Hughes, took up the reins and put his stamp on AWWA affairs. Since then, things have continued to change at a cracking pace. Terminology and jargon generally have moved on, so now the old terms associated with sanitation have some pejorative connotations. AWW A's membership is broader, including people with interests in every facet of water, from environmental flows in rivers to the management of salinity in the landscape . Labels like 'wastewater' have the potential to turn some people off, either because they work in an unrelated area, or because of the negative connotations of dirty water. T here is a growing awareness amongst AWW A members that our current name may not be ideal for the 4

WATER MAY/ JUNE 1999

millennium. Many members now have little to do with 'wastewater' and don't like the connotation anyway-all water is part of the cycle and needs to be valued for its intrinsic properties, not its current condition o r source . A major industry and community debate is looming abou t the merits of taking secondhand water and using it again. This is a debate in which perceptions and prej udices will play a major role. As Angela Makris explained in the last issue of Water, in the modern world much hangs on how people react to the names of products, companies and associations. In 1999 it is quite difficult to sell our modern, outward-looking Association, with its diverse, four-thousand-strong membership under the banner of the Australian Water and Wastewater Association. Apart from any perception issues, there is a very simple practical problem. People who introduce AWWA over the phone find that several repetitions are needed before the 'WW' is comprehended. Trivial, but an impediment to external communications daily. Of course, for members initiated into AWW A, the name ceases to b e important and the value of information and the network are what count. But there is a constant need to sell the Association's meri ts to the community and opinion leade rs, as well as to prospective members. Given that our current breadth of interest and activi ties is n ot sold optimally under the existing name, it is sensible to think about a change. A minimalist and inclusive approach would be simply to drop the word 'wastewater' from the name and become the Australian Water Association. There may well be other names though, so ideas from members will be welcome. Since it is members and their representatives who must decide on a question like this, wide discussion is important. The keys to success will lie in fi nding a name that is appealing to members and the public and inclusive enough to reflect all our interests. What do you think? Chris Davis

From the Top of the Well Freddo is retiring from his role as current affairs commentator in the Water journal since 1996. For those w ho do not know his true identity, he is Peter Hughes, a distinguished Australian engineer w ho has made a major contribution to water engineering in Australia and to the Association. His contributions will be sadly missed as they gave a philosophical insight into the views of many Australians-not socialists, right wingers or democrats-but middleof-the-road, thinking Australians. Peter Hughes served in the RA.AF in Darwin in WW2 and later in the Occupational Forces in J apan, starting his civil engineering degree in 1949 at Sydney University, which included a sandwich work experience period for six months at the HEC, Tasmania. After graduation he joined the Snowy Mountains Hydro Electric Authority and contribu ted to major works. In 1970 he joined the Sydney Water Board, first in the Design Branch and later the Construction Branch, rising to th e position of Engineer in Chief and Assistant General Manager of the Board, from which position he retired in 1986. His involvement with A WWA started in 1976 as Honorary Secretary where he played a major role in the 1976 IAWPRC Conference in Sydney which was run by AWW A. His organisational and interpersonal skills played a major role in restructuring the Association from a comfortable, learned society to a focused, effective organisation responding to the needs of both individual members, sustaining members and the water industry in general. Peter became the first Executive Directo r of AWW A in 1987 in which role he expanded the public profile of the Association and assisted in developing a more releva nt role for AWWA . He was awarded life membership in 1982 and the George Goffin Medal in 1990. In 1993, the Association inaugurated the Peter Hughes Water Award to recognise his contribution to the water industry. Peter achieved a great deal in his eminent career, which was accomplished by technical skills, management of resources, logic, common sense and an ability to get on with people. So Peter Hughes aka Freddo please accept our thanks for your contribution and friendship to your many colleagues in AWWA. We have valued your counsel and wish you, Nan and family a happy retirement. Frank Bishop


INTERNATIONAL

AFFILIATES

INFORMATION AT YOUR FINGERTIPS INTERNATIONAL ASSOCIATION ON WATER QUALITY

Check out the IAWQ websites now!

www.iawq.org.uk Check out the IAWQ site managed and maintained by the head office in London. About IAWQ

Message from the President Taking responsibility for international leadership, by Piet Odendaal.

Conferences

Water Quality International (January/ February 1999) View the contents list of Water Quality International on line.

Publications

IAWQ Corporate Member Directory The directory was updated in Decem ber 1998 and now holds the details of 167 IAWQ Corporate Members. Find out what services and products they can offer you .

Membership

Membership Renewal Form Use this form to pay your membership fee and update your details.

Groups

The IAWQ JobCentre (25 March 1999) IAWQ now provides a listing of employment opportunities (offered and sought) in the water and wastewater sectors.

Waterlinks

Important Dates for IAWQ Conferences Discover deadlines for the submission of abstracts and papers to forthcoming IAWQ co nferences.

Bookshop

Water Science and Technology (Volume 39, 1999)

Directory

Selected Proceedings of the 4th IAWQ Seminar on Modelling and Microbiology of Activated Sludge Processes. The details of earlier issues of Water Science and Techno logy can also be viewed here.

www.iwark.csiro.au/iawq Check out the IAWQ Australian National Committee site managed and maintained by CSIRO. CONTENTS • • • •

What's New IAWQ London Home Page Summary What does IAWQ do? The Australian National Committee of IAWQ Annual General Meetings and other activities Office Bearers • IAWQ Specialist Groups Australia n Membership Objectives of Groups and Coordinators in Australia

NEW

AWWA

ACT P Fogarty, M McGregor New South Wales S Baker, K Bethke, B Budanovic, L Capel, A Darroch, G Illuzzi, P Kelly, M Knight, T Kruf, R Lennings, D Mcl uckie, A Murphy, G Parrett, R Phillips, A Sewell, A Speers, J Stauber, K Umakhanthan Northern Territory G Lombard Queensland C Bullock, H Chapman, K Egan, R Haase, D Harahan, B Harrison, H Holland, R May, T Nugroho, S Petry, I Slape, G Spry, S Temelkoski, L Trott, P Turi, S Vasanthakuma r

• IAWQ Conferences in Australia Guidelines for Organising IAWQ Conferences in Australia Schedule of IAWQ Sponsored Conferences in Australia • IAWQ Conferences Worldwide See: http://www.iawq.org.uk/ conferen/ ca lendar.htm • Twinning with Indonesia See: http://www.eid n.com.au/ iawq.htm • Notice Board Australian Membership (31k) Other Wate r Contacts on the Internet News

MEMBERS South Australia S Blencowe, G Bowden, S Douglas, B Fraser, P Groot, J Howard, J Mitchell , B Nicholson, J Scalzi, M Siebert, T Smith, P Stockham, D Zimmermann Tasmania J Sloane Victoria S Gillespie, L Gough, P Hay, J Haydon, D Hughes, J Oakley, A Skinner, X Smith, M Stevenson, G Verhoef, K Winterbourne Western Australia R Davidson, J Hick, P Jackson, D Ratcheva, K Thornton

WATER MAY/JUNE 1999

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COOPERATIVE RESEARCH CENTRE

FOR CATCHMENT HYDROLOGY

SPECIAL FEATURE

··- - ~.

1111".:~"·J~S'~

Catchment hydrology-the st udy of water-driven processes at a catchment scale-is the subject of this Water special featu re on the work of the Cooperative Research Centre (CRC) for Catchment Hydrology. The CRC exists to improve the understanding of catchment hydrology and its application to land and water management. It is a cooperative venture between: • Bureau of Meteorology • CSIRO Land and Water • Department of Land and Water Conservation (NSW) • Department of Natural Resources and Environment (Vic)

• Goulburn-Murray Water • Melbourne Water • Monash University • Murray-Darling Basin Commission • Southern Rural Water • The University of Melbourne • Wlmmera-Mallee Water with Associates: • Dept of Natural Resources, Qld • State Forests of NSW • Hydro-electric Corporation, Tas Subject to funding renewal, we look forward to welcoming • Brisbane City Council • Griffith University • Dept of Natural Resources, Qld as full participants In the CRC.

COOPERATIVE RESEARCH CENTRE FOR

CATCHMENT HYDROLOGY Centre Office, Department of Civil Engineeri ng, Monash University, Clayton VIC 3168 tel. (03) 9905 2704, fax (03) 9905 5033 email: virglnla.verrelll@eng.monash.edu.au http://www.catchment.crc.org.au/

WATER MAY/JUNE 1999

7


CATCHMENT

HYDROLOGY

MEETING INDUSTRY NEEDS Professor Russell Mein is Director of the CRC for Catchment Hydrology, and an academic In the Department of Civil Engineering at Monash University. He has long held a strong interest In technology transfer, and In this arena Is best known for his co-authorship of the RORB flood estimation computer package and of two books on reservoir yield.

formal agreements. The current group of projects is due for completion this yea r, and shows the variety and relevance of the work the CRC is d oing. The projects are grouped into five program areas: Salinity

• Salt exports from irrigated catchments • Managing disposal basins for salt storage within irrigation areas • Salt exports from dryland catchments

'CRC' stands for Coopera ti ve Forest Hydrology Research Centre and since 1991 more • Sediment sources and movement in than 60 CRCs have been established forestry environments under the Commonwea lth Govern• Im.pacts of forest management on ment's CRC Program. As the Myers Professor Russell Mein catchmen t water balance R eview fou nd in 1995, the letters could equally stand for 'Changing Research both in their management and focus. In • H ydrologic and nutrient effects many ways, the restructuring of the of plantati on growth and eucalyp t C ulture.' Compared with the research effort in government agencies has made the management on a catchment basis hydrology in the 1980s, there is much CRC even more relevant. It is now Waterway Management that is new and different about the filling the research role that used to be • Controlling sediment and nutrient CRC for Catchment H ydrology . W hen provided internally. The current partic- delive1y from hillslopes to streams it b egan operations in 1992, the CRC ipants in the C RC are: • Stream restoration • Bureau of Meteorology brought together th ree hydrological • R eh abilitation and managemen t of • CSIRO Land and Water research groups who used to compete, riparian lands rath er than collabora te. Urban Hydrology The CRC allowed land 'Our initial funding period of seven • Gross poJlutant managemanagers and resea rchers ment and urba n pollu tion to work together 111 years will finish in mid-1999. Along with control ponds p artnership to establish 59 other applicants, we are bidding for • Pollutant sources, movetheir researc h directions ment and modelling 111 and p ri o riti es, formu late a further seven years of funding... The urban areas their projects and conduct Government has allocated resources to Flood Hydrology i nvestigations. It brought CSIRO and industry • H olistic app roac h to provide for perhaps 30 CRC places.' researchers into supervirainfall- based design flood sory panels for post-graduestimation ate students, enriching the students' • Department of Land and Water • Spatial distribution of rainfall and and career Conservation (NSW) research experien ce storm movement using remote sensi ng • Department of Natural Resources • Hydraulic derivation of stream rating prospects. Above all, it provided the funding and e nvironment for research and Environment (Vic) curves • Goulburn-Murray Water to meet future industry needs. Cross-section of CRC Work The changes in the co nduct of • Melbourne Water research during the life of the CRC • Monash University T he articles in this special featu re of • Murray-Darling Basin Commission have been very apparent. We've moved Water represent a cross-section of these • Southern Rural Water from the environment of individual research activities. Of particular note is research to investigation s by mu lti- • The University of Melbourne that th ree o f the articles have been disciplinary teams. Initial concerns • Wimmera-Mallee Water. written by graduate students. T he input Each of these groups contributes cash of energy, enthusiasm and talent from about the overheads involved in setting up project teams from different organi- and/or in-kind resources (stafi~ data, our postgraduates into th e resea rch sations to address issues of concern to equipment, field assistance) which, program has been one of the success industry have been overwhelmed by together with the Commonwealth stories of the CRC for Catchment p ride in the results achieved w ith these contribution, provide the means fo r the Hydrology. The independent panel for new arrangements. Nowadays w hen CRC to condu ct its research and other the majo r fifth year review of the CRC researchers attract audiences of 200 or activities. made special mention of this aspect in more to an industry seminar they get a their report. great deal of satisfaction from knowing CRC Programs An im portant aim for the CRC is to that their work is hitting the spot. The Centre's core research proj ects increase the base of skilled people in the T he organisations that comprise the are generally planned to run for three land and water management industry. CRC for Catchment Hydrology have, years, with objectives, activi ties, and Here, the education an d training in many cases, undergone changes too, staff and student involvement set out in program is an important element, by: 8

WATER MAY/ JUNE 1999


CATCHMENT • involving post-graduate students in research teams to tackle real- life problems • facilitating staff secondments (industry to research organisations, and vice versa) • conducting training courses • holding field days and excursions • including industry representatives on project reference panels • distributing a w ide variety of material (including videos and industry and research reports) • hosting visits from overseas experts The technology transfer program aims to maximise th e take-up of our research by industry and is closely related to these activities. Our initial funding period of seven years will fi nish in mid-1999. Along

HYDROLOGY

with 59 other applicants, we are bidding for a further seven years of funding in the current CRC application round. The Government has allocated resources to provide for perhaps 30 CRC places. By the time this issue of Water is published, we will know ifwe have succeeded. In our application, we have put toge the r a quite new bid. Three Queensland organisations-Brisba n e City Council, Departmen t of Natural Resources and Griffith Universityhave joined with the existing participants, and add substantially to the capabilities and strengths that we have had to date. T he resea rch agenda is very different in focus, with the thrust on p rediction-of wate r, sediment, and nu trient movement-at the catchment

scale. This focus is regarded as essential for the management of catchments in a sustainable way, and to deal with the issues of water allocatio n, the impact of landuse and cover, stormwater pollution an d river restoration. Clim ate variability and the opportunity to reduce hydrologic risk will recei ve particular atten tion. As w ith the previous CRC, t he research directions and projects have been i den tified from scoping workshops, with a wide range of industry and research people involved. The process ensures that the work of the CRC will address the needs of the industry, so that Australia gets high benefits from the Commonwealth investment. That is wha t the CRC fo r Catchment Hydrology is all abou t.

LET'S GET THE HYDROLOGICAL FACTS STRAIGHT! presents us wi th some difficult choices. The establishment of forest plantations appears a logical choice to reduce groundwater recharge. U nfortunately, as former Prime Mi ni ste r Malcolm Fraser once said, life was not meant to be easy. T ree plantations wi ll also substantially reduce streamtlows and the water available downstream. In other words, we may solve one problem with pla ntations only to create another. This dilem ma reinforces the need for sou nd scien tific knowledge as a basis for Dr John Langford decision- making. Australia has a unique environment. T he ability to predict the hydrologiWith the p ossible exception of southern with some answers for the management Africa, we have the most varia ble of these forests. D ecisions ca n now be cal behaviour of large catchments so that management opti ons can be climate in the world and this has had a taken in the light of the facts. Management of salinity is another thoroughly evaluated is a cruci al profound influence on ou r land and water resources. To our cost, we have area where facts based on sound science challenge for hydrologists and resource learnt hard lessons about transferring will help us face the challenges. managers. T he CRC for Catchment European and American experience to Conven tional wisdom has suggested Hydrology h as made predictions of managing land and water resources in that the greatest threat to water catchment behaviour a central feature o f resources is generated by irrigation. In the bid for anoth er seven yea rs o f the Australian environment. In my early career I was involved in fact, the latest research by the funding as a Coop erative Research evaluating the effects of bushfires and Cooperative Research Centre (CRC) Centre. Five focus catchments have been selected for th e clearfelling of mou ndevelopme n t and tain ash (Eucalyptus 'There is no substitute for sound scientific initial applicatio n of regnans) fo rests on hydrological predicwater yield and quality. knowledge if we are to meet the land and tions. Success in this Conventional wisdom water challenges of the twenty-first century endeavor will be at the time was that crucial in delive rstreamflow would be and avoid costly mistakes.' mg cost- effective increased by fire and solutions to the clea rfelling followed by regeneration. In fact, the reverse for Catchment Hydrology demonstrates emerging threat to our water resources occurred. Streamflows were halved that salinity generated by irrigation is that is posed by dryland salinity. T here is no substitute fo r sound once the regenerating forest grew. A m uc h more manageable than the long-term program of hydrological increasing stream salinity generated by scien tific knowledge if we are to meet the land and water challenges of the 21st research started by some far-sighted land clearing in the upland catchments. Management of dryland salinity century and avoid costly mistakes. individuals in the 1940s has provided us

Sound decision-making and the achievement of cost-effective solutions to Australia's land and water management challenges must be based on scientific knowledge. Decision-making In the absence of facts Is likely to result In costly, Ineffective Investment. Board Chairman of the CRC for Catchment Hydrology and WSAA Executive Director Dr John Langford argues the case.

WATER MAY/JUNE 1999

9


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CATCHMENT

HYDROLOGY

source material and sedimen t data, it is possible to de termine the relative proporti ons of sediment coming from different so urces. In this study, relationships betwee n major elem ents were Introduction u sed to d istinguish b etween soils T he quality o f the water from T arago derived from different rock types and R eservoir in Gippsland, Vic to ria is 137 C s conce n trati o ns were used to lowe r th an th at from M elbourne disc ri minate between surface- and subW ater's o the r supply reservoirs. In surface-derived sediment. 1991, the reservoir experie nced a mi nor Both the geoc hemistry and 137 C s toxic algal bloom . At the time phosphodata indicated that the sedi m ent in ru s was considered to be the limiting T arago R ese rvoi r was no t we ll mixed , nutrie nt for algal grow th (H ecky and n or from a uni form so urce (D ye r, Kilham , 1988) and as most phosphoru s 1998). The 137 C s data indica ted that transported in Australian waterways is surfa ce soil erosion was a significant attac hed to particles (Oliver, 1993; contributor o f sedimen t to the rese rC ul le n , 1995), the supply of sediment voir. T he co ntribution from soils and associa ted phosphoru s was co nsidderived from different rock types is ered to be one of the major contribu tors shown in Figure 2 and summarised in to th e poor water quali ty. T o assist Table 1. At the inlet of the Tarago M elbourne W ater target sediment and River to the reservoir, the sedim ent is ph osphorus control measures, a commainly a mix of basalt- and granitebination of field obse rva ti o n s and derived mate rial. Moving away from the sediment tracing techniques was used to Sediment Tracing Sedi m ent tracing involves the inlet of the Tarago River, the contribuidentify th e do m inant contributing co mparison of a di stinctive property (or tion from sedime ntary- derived soi ls areas. fingerpri nt) in potential source material increases and most of th e sedime nt in Tarago Catchment with the same property in sediments. the centre of the reservoir and along the 2 By applying mix ing m od els to th e eastern side is from sedimentaryApproximately 75% of the 114 km de rived soils. The sedime nt ca tchmen t supplying Ta rago signatu re in the western in.lets R eservoir is occupied by state matches those of the soils forest, with the remainder used fo u nd in the ca tchments of the for agriculture (dairying, grazing streams draining into the in.lets. and potatoes) . Just under 1% of Approximately 65% of the the state fo rest is harvested each sediment in th e reservoir is year. Landuse in the ca tchment derived from sedimentary and is closely linked to geological boundaries, with m ost of the basalt-derived soils (see T able 1). agriculture o ccurring in areas The con clusion draw n from underlain by basalt and sedimensedime n t tracing is that the ~ Agriculture tary rocks, and the fores try Forestry Tarago River is not the domioccurring in areas of granite c:J Quaternary alluvium nant source of sediment to the [ J Sedimentary rocks (see Figure 1). reservoir. Instead, the sedimen t ~ Granite has been derived from the slop es • j Basalt Sediment in Tarago arou nd th e reservoir and the Reservoir small drainage basins on each side of the reservoir, predo miThe total volume of sediment Figure 1 Landuse and underlying geology of Tarago catchment delivered to Tarago R eservoir nan tly from surface soils. since its co n stru c ti o n in 1967 was estimated to be 190,000 (¹ 30,000) m 3 (Dyer, 1998) . Th is sedime nt was found to be deepest and coarsest in all the major inle ts and at the edges of the reservoir, grading to shallow and fi ne r at the ce ntre of the reservoir. This suggests that the T arago Rive r (which drains about 70% of the catchment) is not the dominant sou rce of sediment and that all the smaller inflowing streams and adj acent slopes are significa nt contributors. These findings and the exi stence of almost 10 km of eroded shoreline drew attention to th e shores as a contributor of sediment. By mapping the crosssection of the e roded shores, it was estimated that 28,000 (¹ 6,000) m 3 of sedimen t delivered to the rese rvoir (abou t 15% of the tota l) had bee n derived from shoreline erosion (Dyer and Davis, in prep.).

WATER MAY/ JUNE 1999

11


CATCHMENT

HYDROLOGY

Table 1 Contributions of soils to sediment in Tarago Reservoir Source

Volume (m3)

Contribution (%)

38 ,000 ± 6 ,000 Granite-derived soils Basa lt-derived soils 56 ,000 ± 9 ,000 Sedimentary-derived soils 65,000 ± 10,000 Shoreline erosion 28 ,000 ± 6 ,000 Total (includes rounding) 190,000 ± 30,000

Yield (t/km 2/ yr)

Mass (t)

20 ± 3 30 ±5 35± 5 15 ± 3

44,000 ± 6,000 17 ± 3 72,000 ± 11,000 170 ± 30 80,0 00 ± 12,000 400 ± 60 34,000 ± 7,000 1200 ± 200 Vyr 230,000 ± 19,000

Table 2 Mass of phosphorus (P) delivered to Tarago Reservoir from different soil t ypes in the catchment Underlying rock type Granite Basalt Sedimentary Shorel ine over granite rocks Shorel ine over sedimentary rocks

P concentration (%)

Mass delivered (t)

% contribution•

0 .10 ± 0.01 0 .24 ± 0 .03 0.09 ± 0.02 0 .10 ± 0 .01 0 .09 ± 0.02

40 ± 10 170 ±40 75 ±40 30 ± 7 5±2

15 50 25 10

Total delivered attached to soil particles (after rounding)

3 20 ± 60

• rounded to the nearest 5%

Phosphorus Sources

-

Sedimentary derived soils ·

Basalt dorivod soils · · · · · · ·' · · • · · · · · ·' · · · · · A simple mass balance Granite derived soils Mixture of basalt and indicated that all the phossodimontary dorivod soils ·• ·. · . · . •. ·. ·. ·• · Mixture of granite and · · · ·· · · · · · p horus in Tarago Reservoir basalt derived soils (280 ± 40 t in the sediment and M ixture of granilo, basalt and sedimentary up to 5 t in the water colum n) derived soils can be acco un ted for by f2J Quaternary alluvium D Sedimentary th e delivery of p h ospho ru s 0 Granito attach ed to soil particles (320 ± E3 aasalt 60 t) (see Table 2). The relative con tribu tions of ph osphorus from each soil type shows that the basalt-derived soils are t he grea test single co ntributo r of p hosphorus to the reservoir. This is because of the m uch higher concentra:::: ::: ~o~" •,,:, tion of phosphorus in these ~~ soils, rather than a significantly 'S vvvvvvvvv larger contribution of sediment from the basalt-derived soils. Both the basalt- and sedime n tary-derived soils of the catchment are farmed, but the mass balance approach indicates that fertiliser ph ospFigure 2 Sou rce of sediment in Tarago Reservo ir horus would be a trivial component of the total phospho ru s budget for Tarago Reservo ir. Australian inland waterways is associNoting that C ulle n (1995) pointed out ated with fi ne sediment and has been that it is likely that all the phosphorus derived from the natural phosphorus in in reservoir sediments is potentially soils rather than agricultural runoff or biologically available, this suggests that point sources (Caitcheon et al., 1995; the total amou nt of phosphorus is Chowdhury and Al Bakri, 1998). The management implications of this important. research for the reservoir as a whole are Management Implications clear. If it is considered necessary to This CRC study demonstrates that decrease the sediment supply to Tarago most of the p hospho ru s in Tarago reservoir, areas of sedimentary- and Reservoir has been delivered to the basalt- derived soils adj acent to the reservoir in association with th e reservoir need to be targeted. To n aturally ph osphorus-rich basalt soils. decrease th e supply of phosph orus, T hese fi n dings add to an increasing attention needs to be given primarily to body of evidence which indicates that restricting sediment delivery fro m the m u ch o f the phosp ho rus reaching basalt-derived soils. ; V ). ;}' V ~(:,'t)

12

WATER MAY/ JUNE 1999

V

>

V

V • ~ - :; •

V

V

V

V

V

V V V V V V

V

\/

V

V

V

In showing that sedime nt source varies depending on the positio n in the reservoir, this research has also demonstrated the significance of local and shoreline sources for reservoir sedimentation. T his infl uences which areas of the catchment are targeted to control the delivery of sediment and associated phosphorus to specific sections of the reservoir. H owever, before management strategies are developed it should be noted that there is a major pool of phosphorus contained within both the reservoir sediments and the alluvial soils over which the reservoir was built. This means that the reservoir has an internal source of p hosphoru s that can potentially provide phosphorus to the water column fo r many years. T his means that in the short to medium term, red ucing the exte rnal p hospho ru s loads may result in im proved stream wate r quali ty bu t may not imp rove lake water quali ty.

References Caitcheon G, Donnelly T , Wallbrink P and Murray A (1995) N utrient and Sediment Sources in C haffey Reservoir C atchment. Australian j ournal of Soil and Water Conservation 18(2): 41- 49. C howdhury M and Al Bakri D (1998) P hosphorus Inputs to a Reservoir in Orange, NSW. Watcr 25(4): 21-26. Cullen P W (1995) Managing Non- point Sources of Phosphoru s from R ural Areas. Watcr 22(2): 12-15 . Dyer F J (1998) Sources of Sediment and Associated Phosphorus for Tarago Reservoir. Unpublished Ph D T hesis, University of Melbourne. Dyer F J and D avis J A (in prep.). Lake Shore Erosion Rates: T he Infl uence of Lake Size. Hecky R E and Kilham P (1988) Nutrient Limitation of P hytoplankton in Freshwater and Marine Environments: A Review of Recent Evidence on the Effects of Enrichment. Lim nology and Oceanography 33(4): 796-822. O liver R L (1993) Phosphorus Dynamics and Bioavailability in Turbid Waters. Proc. National Workshop on Phosphorus in Australian Freshwaters, Charles Sturt University, pp. 93-103.

Authors Fiona Dyer is a Research Fellow with the Department of Geography, Australian National U niversity. She is a fo rmer CRC graduate student. Jon Olley is a Research Group Leader with CSIRO La n d and Water, P O Box 1666, Canberra ACT 2601. Graham Moore is a CRC Researcher, Department of C ivil an d Environmental E nginee ring, The University o f Melbourne, Parkville VIC 3052. Andrew Murray is Associate Professor, D epartmen t of Earth Scien ces, Nordic Laboratory fo r Luminescence D ating, Ris0 National Labo ratory, Aarhus U niversity, DK-4000 Roskilde, Denmark.


HYDROLOGY

CATCHMENT

TREES ON HILt S BETTER GROWTH = LESS WATERLOGGING R P Sllbersteln, D L McJannet, R A Vertessy Introduction It is somewhat ironic that in the driest inhabited continent, two of Australia's major environmental and agricultural proble1ns stem from a surplus of water. Large areas of agricultural land and natural ecosystems are under threat from waterlogging and salinisation, which will jeopardise all productivity if better land manageme nt Figure 1 Tasmanian is not achieved. The problems stem primarily from a lack of adequate water management. Both waterlogging and salinity problems are symptomatic of a net increase in water recharge to soil, resulting from the replacement of deep-rooted native woodland species with shallow- rooted annual crops and pastures. The major cha racteristics of the native vegetation which gave rise to a balance with the water su pply were that it had perennial leaf cover and an ability to extend roots deep into the soil. These characteristics en su red that the vegetation used water throughout the year and that the vegetation could access subsoil water in summer when the cli matic demand was at its maximum. These critical features are lacking in agricultural crops and annual pastures, w ith the result that their shallow roots are not able to extract water from deeper than about 0 .5 m, and they only use water for about half the year. In summer, the only water w hich leaves the soil-water system does so by soil evaporation and subsurface lateral flow, both of w hich are generally very slow. The CRC for Catchment H ydrology is involved in a number of projects aimed at adjusting agricultural practices and expectations to allow a restoration of the hydrologic balance in the agricul-

. ¡"

bluegu m plantation at Warren bayne

tura l environment. We are investigating the extent to which returning a proportion of the land to deep-rooted trees will restore the water balance, what the likely impact of this restoration will be, the time scale for land recovery and the likely economi c cost or be nefit to landholders. In hydrologic terms, we can use tree planting on farms, or 'agroforestry' as it is often called, to collect excess available wa te r flowing through the soil and prevent it causing problems further downslope. Thi s requires that the combination of soil hydraulic conductivity and piezometric slope be high enough to meet the plantation demand. Under these conditions, trees can be planted in relatively w idely spaced belts, each having several rows of trees which can intercept the subsurface lateral flow before it accumulates in problem areas downslope. In this article we describe a field experiment and comp uter modelling study undertaken at a site in central Victoria where trees are being used to tackle waterl ogging problems.

Field Site The study site is located 111 Warrenbayne, on the edge of the Strathbogie R anges, about 15 km from Benalla in Victoria. Landuse is predominantly sh eep grazing. The average

annual rainfall at the site is 871 mm, soils are deep (4-12 m) colluvials with a moderate hydraulic conductivity (generally up to 0.2 m/day) , but with occasional clay lenses having quite low conductivities m/day) (0 .001 which pose a significant barrier to water flow and often support a perched watertable in winter. In August 1992, a plan tation of Tasmanian bl uegums (Eucalypw s globulus) was established towards the uppe r half o f a hillslope, covering about 24% of the hillslope area, in an attempt to dry up a waterlogged area at the base of the slope (see Figure 1). The plantation covers an area of about 6 ha and was planted at a density of 1,100 stems/ha. The plantation was designed to take advantage of a perceived shallowing of watertable near the break of slope, w here the hillslope has a relatively rapid change in gradient. A section of the plantation, having an area of 2.2 ha, with the land upslope and downslope of it, was chosen for the study. Figu re 2a shows the location of the plantation w ith the element mesh used to simulate hillslope. Since 1996, a climate station recording net radiation, rainfall, humidity, temperature and wind run and direction has been installed in the paddoc k downslope of the plantation. Plantation leaf area index has been measured pe riodically, between 1995 and the present, and wood volume estimates have been made annually since planting. In 1996 and 1997 a severe drought in the area began to impact on the trees, with deaths beginning in August 1997 . At this time three plots in the plantation were thinned to densities of 400, 600 and 800 stems/ha, in order to study the effect that thinning would have on the WATER MAY/JUNE 1999

13


CATCHMENT water use of the trees, and to determ ine whether thinning could alleviate the moisture stress the trees were encountering. Since that time the water use of 10 to 20 trees distributed through the three plots has been monitored . The water use of each plot has been calculated scaling up from these tree measurements on the basis of sapwood area.

Modelling

HYDROLOGY

Total wood volume (m3 ha-1)

360

(b)

330 300 260

Figure 2 Model element network and predicted wood val ue at

the trees 1s significantly enhanced by the breaking up of the plantation into strips. This has importance for the design of similar plantings at othe r sites. Also of significance i s the fact that this en hanced growth is accompanied by, and largely due to, an increase in water consumption by the trees, w hich has therefore improved waterlogging control downslope. Field measurements have shown that trees in t he Warrenbayne plantation are sourcing their water from the top 0.5 m of soil (McJannet, et al., submitted). This goes some way to explaining the greater growth and water use o f the strips. Because the t rees are not accessing t he watertable the importance of water supply via surface and subsurface lateral flow from up slope is greater. The strips have an advantage over the single wide belt because each strip is able to use lateral flow from pasture areas upslope . In the tree belt situation, trees further up the slope have been shown to rob the downslope trees of access to this water. This ca n be seen in Figure 2a, which shows that growth declines with distance from the upslope edge of the block plantation, and also to some extent in the strip planting (Figure 26).

Modelling the wate r Warren bayne balance and vege tation 5 . . . , . . - - - - - - - - - - -- - -- - - - - - , growth at this site has been - Predicted LAI (24 12) (a) undertaken using the - Predicted LAI [28 2) TOPOG model (Vertessy et - Predicted LAI [29 6) 4 al., 1995; 1996), which uses - Observed LAI Richards' equation fo r vertical 3 moisture flow in multilayered soils, Da rcy's Law for lateral saturated flow, the convection2 dispersion equation for solute transport, and evapotranspiration based on the PenmanMonteith model. Soil water extraction 1s through a distributed root syste m from the multilayered soil, an d - Predicted wood volume (m 3 ha路1) (24 12] (b) - Predicted wood volume (m 3 ha路1) (28 2) there is water in terchange - Predicted wood volume (m 3 ha路 1) (29 6] 80 with the underlying aquifer - Observed wood volume (m 3 ha路 1) system. A p hysiologically based plant growth module 60 allocates carbon to root, stem, branch and leaf compart40 ments, depending on water, nutrient and light availability, ambient temperature and soil 20 salinity. Thus plant growth, water u se and soil-water Conclusions solute dynamics are closely 1 / 1 / 93 1 / 1 /94 1 / 1 /95 1 / 1 / 96 1 / 1 / 97 1 / 1 / 98 linked. T he close agreement betIn this study we have ween observed and predicted Figure 3 Observed and predicted leaf area index (LAI) and modelled the plantation wood volumes at Warrenbayne. Selected elements are in square values of leaf area index brackets. Dots are measurements. growth and water use as it is, and wood volume for the and as four strips covering the plantation gives us confidence same area . W e used an historical 20- selected set of representative network in the results being produced from year climate series to predict growth elements, with the average measured sim ulations. into the future. Figu re 2 shows the values for the plantation. These results Through the simulations we were location of the existing plantation (2a) show close co rrespondence betwee n able to predict the water use and growth on the hillslope and the representation observed and p redicted values for the of the plantation under its curre n t as four strips (26). T he colours indicate first five years of simulation. configuration and show how it could wood volume after 20 years for each Also (not shown), the simulated rate perform in the future. It is acknowlmesh element. We have also used the of plantation growth declines after the edged that the inability of the model to model to investigate how changing the first fi ve yea rs, and th is has been simulate tree mortality during times of plantation configuration wou ld affect observed in the field, mainly due to the drought is a weakness. H owever, the water u se and growth. To do this we onset of a severe drought. One of the strength of the modelling lies in its have set up a hypothetical planting wea knesses of th e model is that i t ability to predict relative differences in which has the same total area under cannot predict t ree deaths resulti ng growth and wate r consumption for trees, but the trees are arranged as four from drought stress, although it does diffe rent plan tation designs. strips across the hillside. predict a slowing of growth rate. Our We conclude that for landscapes w ith observations in the field have shown deep and relatively permeable soils (as at Results and Discussion that 25% of trees died during t he Warrenbayne), m ultiple thin belts are the optimal tree planting configu ration The results of our simulation of the 1996/97 drought. Figure 4 compares the predicted to maximise water balance and tree plantation on the hillslope are shown in Figure 3. We show the simulated leaf growth of the trees configured as a growth objectives. T he strip configuraarea index (LAI) and wood volume fo r a block and as four strips. The growth of tion allows surface and su bsurface 14

WATER MAY/JUNE 1999


CATCHMENT Mean Annual Rainfall 1000 800

e

s.

600

~

400

:;; a:

200

Year 1·5

20 -

·- ...,

Yea r 6-10

I

Year 11-15

Year 16-20

Mean Annual lricremenl

HYDROLOGY runoff from inter- strip areas to be captured by trees, potentially enhancing their growth and water use. This finding is supported by the observations at Warrenbayne w he re runoff from areas above the plantation has enhanced tree growth and water use of the top edge of the plantation. Thjs researc h de monstrates h ow T O POG_Dynamic can be used as a powe rful modelling framework for assessing the effectiveness of different plantation configurations.

15 1

2 'k

Reference 10 •

< :i;

Year 1-5

Year6·10

Year 11-15

Year 16·20

Mean Annual Eva.potransplratlon

Authors

2000 -

I,soo .§ e

l ,ooo

!

500

J

Year 1-5

Yoer 6-10

McJannet D L, Vertessy RA and C lifton CA, Observations of Evaporation in a Break of Slope Plantation Susceptible to Periodic Drought Stress. Submitted to Tree Physiology.

Year 1H5

Year 16-20

Figure 4 Rainfall, tree growth and evapot ranspi ration from the block plantat ion and four strips simulated over 20 years

Richard SIiberstein is a CR.C Project R esea rcher with CSIR.O Land and W ater, GPO Box 1666, Canberra ACT 2601. David McJannet is a CR.C gradu ate student with th e D epartment of C ivil Engineering, Monash U niversity, Clayton VIC 3168. Rob Vertessy is D eputy Director, Program Leader Forest Hydrology, C R.€ for Catchment H ydrology, CSIRO Land and Water, GPO Box 1666, Canberra ACT 2601.

The first comprehensive guide for wetland projects in Australia is available now!

water Contributions Wanted T he Water journal welcomes the ~ubmi~~ion of papers of 3,000-5,000 words relating to all areas of the water cycle to be published in the water, wastewater, environment and business sections of the j ournal. The deadlines fo r submission of papers to Water during 1999 are: 21 May • Sept/Oct 20 Jul • Nov/ D ec Please send two hard copies and one soft copy plus figures and graphics to Features Editor Bob Swinton, 4 Pleasant View Crescent, Gle n Waverley Vic 31 50, email swin tonb@c031.aone.net.au. (Colour photographs to be saved o n a Zip 100MB disk as tiff or EPS Macintosh or Tif P C format, CMYK mode, 600 dpi resolution. Black & white photographs to be 1200 dpi resolution. Otherwise, send transparencies or good quality prints.) Topical, magazine-style stories of up to 2,000 words can be submitted closer to the publica tion date by arrange111ent with General Edito r Margaret Me tz, tel. (02) 9413 1288, PO Box 388, Artarmon NSW 1570, email m me tz@awwa.asn.au.

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WATER MAY/ JUNE 1999

15


CATCHMENT

HYDROLOGY

Introduction In a recent issue of W ater, C lean Up Australia Chairman Ian Kierna n stated that 'the days of discharging untreated effiuent into th e ocean or rivers, while draining our rivers of precious flow, are numbered' (Kiernan, 1999). This sentiment has become increasingly common in the water industry and w ider communi ty in the last few years. The CSIRO Urban Water Program, th e Queensland Water R ecycling Strategy and the CSIRO report, W astewater Reuse, Swrmwater Management and the National Water R eform Agenda (Thomas et al. , 1997) are a few examples of recent research programs, government ini tiatives and repo rts which are driven by the aim o f red ucing th e environmental impact of Australia's water use and disposal. There is much to learn and many ch allenges to face before we, as an indu st ry, know t he best ways to n1.inimise th e enviro nmental impa ct of providi ng water supply and disposal services. But, significant inroads have been made in recent years and with the curre nt momentum and given time, the re will be a fu!Jer understanding of how water supply and d isposal services of th e future can achi eve the goal of 111.inimising our impact. The CRC for Catchme nt Hydrology has contributed to the understanding of how to modi fy urban water supply and disposa l practices by research and development of an urban water balance m odel, AQUACYCLE. T o date, there has been a lac k of tools to evalu ate the feasi bili ty of u rban stormwate r and wastewate r reuse sch emes at anything fin er than the broad-brush scale. AQUACYCLE addresses this by allowing the simulation of a variety of reuse sc hemes. Scenario analysi s of reu se sch emes using AQUA CY C LE predicts a reduc-

tion of up to 65% in mains (imported) water co nsu mption through the use of stormwate r and/or wastewater in urban areas. These predictions are co nsistent with observations made at Figtree Place, a water- sensitive urban redevelopment in Newcastle (Coombes et al. , 1999) . This paper briefly desc ribes the key features, conceptual structure, performa nce and limitations of AQUACYCLE.

evapotranspiration

irrigation

non ettective area runott roo

runott infiltration store recharge

road

paved

impervious surtaces

pervious surtace

impervious surtace runott

indoor water use

I

l nliltratlon 'lj store~ -

leakage

~

infiltration inflow~

L

groundwater storage base ~---------flow

wastewater discharge

stormwater runoff

Figure 1 Structure of the current urba n water cycle represented by AQUACYCLE

What is AQUACYCLE? AQUACYCLE is a model used to carry out what-i f scenari o modelling of traditional and alternative urban water supply and disp osal schemes. The water balance approach used to develop it accounts fo r the movement of water t hrough bot h the rainfall- runoff n etwork and the supply- wastewater network, as well as cross-links between the two . As a result, the wate r supply, stormwater drainage and wastewater disposal are integrated into a single fram ework. This is a unique aspect of th e model. The key features of AQUACYCLE are given in Table 1. The m odel inpu ts both precipitation and imported water. T his passes through the system, w hich ou tputs evapotranspiration, stormwater o r wastewater. AQUACYCLE can 'sto re' stormwater and wastewa ter sepa rately and use them as supply sources for sub-potable water applications according to user specifications. H ence, the outputs of stormwater and wastewater can be re-routed back into the urban water system as water supply sources. In order to model a wide variety of schemes, AQUACYCLE uses several spatial scales (uni t block , clu ste r and catchment). The unit blockWATER MAY/ JUNE 1999

17


CATCHMENT

HYDROLOGY

Table 1 Key features of AQUACYCLE Item

Descri ption

Temporal scale Spatial scales Surface types Input requirements

Dai ly time step Unit block, cluster and catchment Pervious, roof, paved and road Site cha racteristics Indoor water usage profile Daily precipitation and evaporative demand series

Operations Unit block scale

Cluster sca le

Catchment scale Supply and disposal options Unit block scale

Cl uster scale

Catchment scale

Model output

~E

it

Indoor and outdoor water use Stormwater runoff Groundwater recharge Wastewater discharge Evapotranspiration from roof, paved and garden areas Unit block scale stormwater and wastewater reuse schemes Stormwater runoff from road surfaces and publ ic open space Leakage of the ret iculation system Inflow and infiltration of stormwater into the wastewater network Groundwater recharge, storage and base f low Evapotranspiration from road and public open space areas Cluster scale stormwater and wastewater reuse schemes Catchment sca le stormwater and wastewater reuse schemes Imported water Rain tank Direct sub-surface greywater irrigation On-site wastewater treatment and reuse Imported water Cluster scale stormwater storage and reuse Cluster scale wastewater treatment and reuse Aquifer storage and recovery Imported water Catchment scale stormwater storage and reuse Catchment sca le wastewater treatment and reuse Stormwater, wastewater and imported water use Stormwater and wastewater yield Evapotranspiration Storage status Performance of selected reuse options

30

Structure of AQUACYCLE

"ti

m

25

0

-

20

Precipitation Recorded stormwater flow

·6" ~

g-

50

-" 3

§ 10

;!_

75

iii

0-1--1--=="""''-'==,,-.--".....,_'-"'-P-.....,_--....u.;-.L.1-Jul-BB

Aug-BB

Sep-BB

...u.-

Oct-BB

a.

+>--...Ll...=..c"-'--+'-"'-'-_,_l-.L..u.100 Nov-BB

Dec-BB

Figure 2 Hydrograph of daily simu lated and recorded stormwater f low, Yarral umla Creek

~

°iF

25

E

;;-1.0

"

-;;· ~

g

s

50

i

75

5'

_:,

~ 20.5

3

0.0 + - - - - - + - - - - - + - - - - - - + - - - -- - + - - - - - - + -Jul-92

Aug-92

Sep-92

Oct-92

Nov-92

!

- ---' 100

Dec-92

Figure 3 Hydrograph of daily simulated and recorded wastewater flow, Woden Val ley

~E

40

0

30

25

t

_:,

~

~

3

10

75

0 -1--1--==""""'-'==,,-......~,__,_..,,_;i....,>_,__,_____,_,_+--'-'----'-'--Jul-BB

Aug-88

Sep-BB

Oct-SB

+>-- ...L..1..cLl.L..>--fL'L-..l.--'--'---L...U. 100 Nov-SB

Dec-BB

Figure 4 Hydrogra ph of weekly simulated and recorded water use, Woden Val ley

18

iii

g

50

.21

en

"ti m 0

-g:

:: 20

WATER MAY/JUNE 1 999

representing a residential house lot or an industrial site-is the smallest scale at which water supply and disposal can be managed. A cluster represents a neighbourhood and co n si sts of a number of unit blocks as well roads and public open spaces. The catchment scale model is made up of a number of clusters. The clusters contained in the catchment may or may not have significantly different characteristics such as residential density, landuse, percentage of impervious area and hydrologic response to a rainfall event. Because the factors which determine the quantity of stormwater and wastewater available and the demand for water can vary significan tly, the user is expected to input information about the area being modelled. If this information is not available, the user can make assumptions and then test the sensitivity of results.

;!_

a.

Figure 1 shows the stru cture of AQUACYCLE. The configuration of pervious area su rface stores and groundwater store is based on A WBM, a partial area saturation overland flow model (Boughton, 1993). The use of partial areas divides the ca tchment into regions which produce runoff during a rainfall-runoff event or 'contributing areas' and those which do not (va n de Griend, 1985) . These con tributing areas vary within a catchment according to th e antecedent catc hment conditions and allow for the spatial variability of surface storage in a catchment. The u se of the partial area saturation overland flow approach is simple and provides a good representation of the physical processes occurring in many Australian catchments. Th is is because daily infiltration capacity is rarely exceeded and the major source of runoff is from impervious and/o r saturated areas (Chiew et al., 1995). W hen one or both pervious surface stores are saturated, excess rainfall is divided into pervious surface runoff, recharge of the groundwater and stormwater infiltration into the wastewater system according to the parameters set by the user. T he groundwater store then drains according to a simple recession function, creating base flow. Actual evapotranspiration from pervious areas is calculated as a linear function of soil moisture based on Boughton's (1966) simplificatio n of the work of D enmead and Shaw (1962). This is calculated separately for each of the two pervious area storages. Impervious surfaces such as roof, paved and road areas are represented as a single store which overflows when full. The concept of 'effective impervi-


CATCHMENT ous area' is used to represent the proportion of impervious su rface runoff which directly drains into the stormwater drainage system. The remainder of the impervious surface runoff drains onto adjacent pervious areas. The water retained in these stores represents the initial loss ofrainfall due to interception and depression storage. These impervious surface stores are depleted by evaporation. The inflow of stormwater into the wastewater system is estimated as a proportion of the total surface runoff generated and enters the wastewater system directly. Leakage is calculated as a userspecified proportion of the imported water and added directly to the grou ndwater store. Water use is separated into indoor and irrigation compone n ts. Indoo r consump tion is furt h er disaggregated in to kitchen, bathroom, laundry and toilet. The amount of water required for indoor uses the refore va ri es with household occupancy and is specified in an input file. Ali indoor water use is normally discharged to the wastewater system. The quantity of irrigation water app]jed to gardens, parks and spo rtsgrounds is infl uenced by the wate r requiremen ts of the plants being grown and the personal standards of the gardener. The decision to irrigate has been formu lated as a fu n ctio n of min imum soil wetness. Irrigatio n water is applied whenever the soil wetness level drops below a trigger level specified by the model user and can be calibrated to fi t the observed garden water patterns of the area b eing simulated.

AQUACYCLE Performance To date, there has been limited testing of AQUACYCLE. The testing th at has been done used data collected in Woden Valley, Canberra. The model performed well in this catchment, but needs testing on catchments that have significantly diffe rent characteristics su c h as cli mate, landuse, drainage methods or topography. Figu res 2- 4 illustrate the performance of AQUACYCLE in simulating water consumption, stormwater runoff and wastewater discharge at Yarralumla Creek in Mawson and Woden Valley in Canberra.

Limitations Currently, AQUACYCLE provides no prediction of water quality. T he range of stormwater and wastewater reuse options available in the model has been selected on the basis of water quality requirements. For example, a user can select untreated greywater as a source for direct sub-surface irrigation, but not fo r drinking water.

HYDROLOGY

AQUACYCLE can store and reuse stormwater and wastewater according to user specifications

There is no flow routing within the model since it has been developed to assess the total quantity of water movi ng through the urban water cycle and not estimate peak flow or produce an event hydrograph. In most urban catchments, all su rface ru noff wou ld flow ou t of the catchment in a matter of hours. Therefore, there is no need for flow routing when usi ng a daily time step. Several urban hydrological processes are not included in AQUACYCLE. These include the application of imported water to impervious surfaces, th e overflow of wastewater, stormwater pipe infiltration and leakage, and wastewater pipe leakage. T hese processes were omitted because they usua lly represent minor pathways of flow in the total urban water cycle.

Availability of AQUACYCLE T he AQUACYCLE software and accompanying user manual will be available in 1999 from the CRC fo r Catchment H yd rology. The software is written in MS Visual Basic TM Programmi ng system for Windows™ as a stand-alone computer application and may be run in Windows 95™. It is assumed that the user is familiar with the operation of standard win dows features such as pull down menus. To use AQUACYCLE, a user would need access to the followi ng minimum hardware and software requirements: a 3¼" floppy drive, with at least 32 Mb of random access memory (RAM), a hard disk with 50 MB of available disk space for installation and simulation results, pl us a windows-compatible pointing device.

References Boughton B C (1966) A Mathematical Model for Relating Runoff to Rainfall

with D aily Data, Civil Engineering Transactions, Vol. CE8 (1): pp. 83-97. Boughton W C (1993) A Hydrograph-based Model For Estimating The Water Yield Of Ungauged Catchments, Hydrology and Water Resources Symposium, Newcastle, IEAust, pp. 317-324. C hiew F H S, Osman E H and McMahon T A (l 995) Modelling Daily and Monthly Runo ff in Urban Catchments, The Seco nd Internatio nal Symposium on Urban Stormwater Management, Melbourne , Australia, Institute of Engineers Australia, pp. 255-260. Coombes P J, Kuczera G Argue J R , Cosgrove F, Arthur D, Bridgeman H A, Enright K (1999) Design, Monitoring and Perfon11ance of the Water Sensitive Urban R edevelopment at Figtree Place in Newcastle. Unpublished paper, Dept of C ivil, Surveying and Environmental Engineering, University of Newcastle. D enmead O T and Shaw R H (1962) Availability of Soil Water to Plants as Affected by Soil Moisture Content and Meteorological Conditions, Agronomy journal, Vol. 54 (5): pp. 385-389. Kiernan I (J999) Australian T echnology for a Cleaner World, Water, Vol 26 (1) p. 3. Thomas J F, Gomboso J, O liver J E, Ritchie V A (1997) Wastewater R..euse Stormwatcr Management and the National Water R eform Agenda, CSIRO Land and Water, R esearch Position Paper 1, C anberra. van de Griend A A and Engman E T (1985) Partial Area Hydrology and Remote Sensing, journal of Hydrology, Vol. 81: pp. 211-251.

Authors Grace Mitchell is a Researcher with CSIRO Division of Building Construction and Engineering and a forme r CRC graduate student, Professor Russell Mein is D irector of the CRC for Catchment Hydrology and Professor Tom McMahon is Deputy Director, Program Leade r Urban Hyd rology, CRC for Catchment Hydrology. WATER MAY/JUNE 1999

19


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CATCHMENT

Introduction The build-up of salin ity in irrigated ar eas in th e Murray-Darling Basin an d the associated exp ort of salt are se riou s problems. Salinisa tion has major impacts on the su stainability o f prod u c tive agricultural areas an d on dow nstream e nvironmental q uality. A de tailed fi eld expe rimen t of w ater movemen t and salt transport w ith in a border-irriga ted bay in no rt h ern Vic toria has been carried ou t by the C R C fo r C atchm en t H ydrology. The area is characterised by sha llow groundw ater tables and salinisa ti on problems. The aim of the study was to monitor ch ange in irrigation managem ent and to re late and quantify its impac t on salt and water m ovement within and from the bay and on recharge to the region's sh allow groun dwater table. Spec ific objec tives of th e project we re to: â&#x20AC;˘ unde rstand and descri be salt moven1.ent processes o ccurring w it hin an irrigation bay â&#x20AC;˘ develop and use an ' irriga tio n bay scale' compu ter model to estimate the sen sitivity of salt m ovement to changes in irrigation management.

Salt Export from Barr Creek The Barr C re ek catchment is an inten sively irrigated area of no rthern Vic toria. 'B order irrigation' is the most com m on form of irriga tion , growing p asture for dai ry or sheep production. T h e area has a saline grou ndwa ter table within 1- 2 m of the soil surfac e. It is a regional di scharge zone, which prevents the natural deep drainage of the irrigation wa ter. The supply of irrigatio n water to an area brings with it a considerable

HYDROLOGY

amo unt of salt, adding to the large store o f salts already present in the soil and groundwater. This leads to increasing soil sali nity, parti cularly near the soil surface wh ere pasture crop s extract wa ter and leave behind the salt. T o di splace thi s sa lt, sustainab le irrigatio n requires flu shing and efficien t drainage to remove the excess wa te r and salt. T his d rainage may be downwards thro ugh natu rally porous soils above good underlying aquifers or through so me fo rm of e ngineered d rainage. Large surface drain s we re excavated in the 1930s using the existing Barr C reek as a main d rain into the Ri ver M urray sys tem. Whi le this reduced the effects of sali nity and waterlogging in the area, it has also resulted in a mea n an nual export o f around 200,000 tonnes of salt with the surface drainage from the area. T his amount ca n vary largely,

depending on rainfa ll. Part of the key to controlling this large salt exp ort is the investigatio n of key wate r and salt moveme nt processes. Un derstanding the processes leading to salt export needs to occur at several scales: regio nal, sub-catchme nt and farm/bay scale. This knowledge can be used to targe t changes in irrigation management practices and their possible impacts on salt expo rt and irrigation sustainability. Seve ral previous studies h ave estimated the relative contributions of these processes to salt export. H owever, th ese relied on regionally applied estimates and total export values. These large-scale studies, while useful , need to be supported by detailed measurements obtained from smaller farm/bay- scale studies of the p recise sources of regional salt load.

Evapotranspiration Groundwater table

Deep recharge

Figure 1 Irrigation bay water movem ent and salt transport WATER MAY/ JUNE 1999

21


CATCHMENT

Ta ble 1 Irrigat ion bay measurement techniques

2,000

!, 11,soo ~

i

....... 2.0 hours

-

3.9 hou rs

.. ~ .. 5.5 hours --&-

6. 7 hours

1,000

~

;

s

/'

500

i

0

HYDROLOGY

0

50

100

150

200

Physical variable

Instru ment and technique

Irrigation supply volume and sa linity Drainage volume and salinity Surface water depth and sa linity

Rectangular flume 1,150 mm wide, manual salinity Tra pezoidal fl ume 200 mm wide, manual salinity Manual measurements at 10 su rveyed pegs along central transect Logged observation wells (2 m deep, 6 locations) Capa citance probes (4 dept hs, 6 locati ons) and manual soil sam ples On-site climate station: t emperature, relative hu midity, wi nd, sola r radiation and rainfa ll Manual soil samples analysed in lab (EC1:5 test) (6 locations, 0- 750 mm dept h)

Groundwat er elevatio n Soil moisture cont ent 250

di$tance from supply channel (m)

Evapotranspiration and rainfal l

Figure 2 Ove rland flow sal inity during irrigation advance

Soil sali nity

20 - - - - - - - - - - ~ 2000 IB

1B

_ 16

1600

~ 14 :::!. 12

l

t

, :. :~: : ,...

- :~;ity

·-

'5

4 2 0

1400 ~

,....

,o

1200 ~ 1000] 800 600

400 200

~

w

o

f

t~

~

0

20 m lime from start of lrrigation (hours)

Figure 3 Drainage flow and sali nity during an irrigation event

500 salt export

/1 5/4

400

oi

, , '. 26/3

6

<ii U)

300 25/9

<1)

Ol

"' C:

·~

200

-0

• 26/1

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.

4/12 100

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, , 20/ 10

• 15/1

Irrigation Bay Study

, , '9~11 •• 20/2 00

100

200

salt import

300

400

500

irrigation supply salt (kg)

Figure 4 Measured salt export ratio for irrigation events, 1996/97 season

Typical Irrigation Event In border irrigation, each fa rm is divided into sloping paddocks or 'bays' separated by low earth ch eck banks an d served by both i rrigation supply and drainage channels. These bays are irrigated indepe nd en tly, forming the basic unit for on- farm irrigation management. During each irrigation event, water is supplied from a farm channel at the upper end of the bay, moving slowly down the bay as overland flow over several hours, w hile a portion of this water infiltrates into the soil. T he water supply is cut off w hen the irrigator judges that sufficient water has been applied . T he exact timing of cut-off varies , but is typically when the advancing water has reached about two thirds of the distance down the bay. This takes be tween 3- 10 hours, dep ending on the size of the bay size and the flow rate. After cut- off, the water on the bay surface conti nues towards the lower end, increasing in salinity as it dissolves 22

salt from the soil surface and moves laterally down the bay. Water reachi ng the shallow drain at the end of the bay flows into the farm drain and finally into the regional drain network. In o rder to u nderstand the factors influe ncing the volum e and salinity of irrigation ru noff, it is useful to sep arate an irrigation bay into interlinked processes. Important processes include input to the system such as irrigation and precipitatio n, outp ut from the sys tem such as drain flow and evaporation and the intermediate processes of infil tration, overland flow , groundwater movement and capillary rise. By simplifying bay behaviour, the relatio nships that d etermine bay responses can be more clearly understood . Figure 1 ill ustrates the main irrigation bay processes.

WATER MAY/ JU NE 1999

A key part of th is C RC study was the exte nsive monitori ng of an irrigation bay si tuated in the Drain 14 subca tc hmen t o f Barr C reek. T h e bay measured 280 111 by 55 111 in size and had a 1:750 slope. Salt and wa ter movement was measu red to investiga te how much, and at what times, salt was transported into the su rface drainage network. D e tailed da ta were obtained fo r surface and su bsurfa ce variables over the 1996/97 irriga tion season. Although all bays are slightly different, the ch osen si te was considered to be reasonably representative of 'typical' conditions in the area . The upper part of the bay was an A C lass soil, while the lower part was C Class and exhibited significan t signs of sa!inisation. T he bay w as sown with perennial pasture and was not an ex treme example of size or slope in the area. Several different techniques and instruments we re used to measure the complex movem en t of w ater and salt in the bay (see T able 1). Since reliable field m easuremen ts can be difficult to obtain, the monitoring sc hedule was kept flexible to include both lo ng-te rm and sh ort- term m onitori ng . The data obtained were used to estimate the effects of irrigatio n on the mobilisa tion and export of salt from the bay.

Salt Mobilisation As the i rrigatio n wate r advan ced down the bay, it dissolved some of the salt fro m the soil surface . This mobilisation of surfa ce salt happen ed very quickly, with a distinct lateral movement of salt (see Figure 2). T he increase in surface water salinity was greater as the water flowed over the lower part of the bay. During the recession stages o f irrigation , the surface water salinity increased, particularly i n the lower part of the bay. H owever, m uch of this increase occ urred whe n the drain had almost stopped flowing, so little o f this salt could be exported from the bay in drainage. Salt from the surfac e and n ea rsurface parts of the soil was mobilised into the surface irrigation water very quickly during irrigation. The presence of soil cracks, particularly in the lower part of the bay, enhanced this effect due to the increased soil surface area. The rate of mobilisa tion of salt from the soil gradually decreased over th e course of a single irrigation event. T his supported the conclusion that lateral washoff of salts from the bay surface was the main process of salt mobilisation during irrigation in areas with poor d rainage and a shallow groundwater table.

Salt Export N ot all of the salt mobilised during an irrigation event was exp orted from the bay in the drainage water. Although salts from th e soil surface we re mobilised quickly, the relative m agnitude of the irrigation event determin ed how mu ch of this salt w as actually exported . Drainage flow typically reached its p eak value around 1- 2 h ours after it h ad begun to flow. T he reduction in flow took much longer , w ith flow ceasing about 25- 30 hours after the start of irrigation. Figure 3 shows the ch anging flow into the drain over time and salinity changes for a typical irrigation event. T he salinity at the start of drainage flow was high (1,500-2,000 µ S cnr 1) , but dropped rapidly during th e rising part of


CATCHMENT

the bydrograph. This initial elevatio n in salinity was due to the was hoff of surface salt (see Figure 2). As this high salinity was restricted to water close to the advancing front, drainage salinity dropped rapidly as the less saline water from behind the front reached the drain. After the peak in drain flow, the salini ty gradually rose over the remainder of the event.

Regional Salt Export Over the 1996/97 irrigation season , the surface salt export ratio was close to a balance (sa lt expo rt with surface drainage/ salt import with irrigatio n = 1 = 100%). There was variation in the amount of salt exported from the bay with drainage for each irrigation event. Figure 4 shows the salt export ratio (salt exported with drainage vs salt imported with irrigation) for eac h of the measured events of the 1996/97 season at the monitored irrigation bay. Poin ts above the 1: 1 line indicate a net salt export. The approximate balance over t h e entire season indicated that although the monitored irrigation bay exported salt , it did not contribute to the large regional salt export ratio. Given the extremely high regional salt export ratio, th e irrigation bay's net salt balance was surprising. T he local sub-catchment (Drain 14) had a large salt export ratio for the 1996/97 season of 400%. It had been expected that irrigation bays would be a major direct contributor to the regional salt expo rt ratio , as they form the basis for irrigation water application. This discrepancy between the irrigation bay and the local area suggests that if all irrigation bays in the area are in a salt balance, irrigatio n runoff

HYDROLOGY

contri buted only around 25% of the total salt load from Drain 14, a rela tively minor contribution. The 1996/97 seaso n had very low rainfall (implyin g minimal rainfa ll runo ff). Th is suggested that th e rema111111g 75% of the Drain 14 sal t load originated from direct groundwater flow in to the regional drains. This finding has important implications fo r the management of salt export from the area. If irrigation runoff is only a minor contribu tor to regional salt loads, even a significan t decrease in runoff volumes from bays will only have a small regional effect.

Possible Irrigation Bay Management Changes W hile excellent measured data was obtained for almost an enti re season of irrigation eve n ts at a single bay, a computer model was used to add confidence to the assessment of irrigation bay behaviou r. T he Bay Scale Model was developed by the CRC for Catchment H ydrology and is a physically based model that can simulate and predict both water and salt movement in an irrigation bay. T he model uses data on irrigation su pply, evapotranspiration, rainfall and physical bay characteristics to simulate the interactions between su rface and subs urfa ce processes. As well as using physical characteristics of the

monitored bay, some model parameters were fitted during the calibration with m easured resul ts from the monitoring study. The ability o f th e model to simulate behaviour an d match measured results provided confidence in its output. This enabled the sensitivi ty of irrigation bay processes to individual changes to be estimated more readily than with measurements alone. An understanding of th ese processes can be used to make recommendations about the effects of changing various irrigation management options. Possible irrigation management changes are: â&#x20AC;˘ reducing irrigation event volumes â&#x20AC;˘ cha nging the salinity o f supplied irrigation water. The con sequ e nces o f t hese two options, as determined from both measu red data and modelled scenarios, are discussed below.

Reducing Irrigation Volume By applying less irrigation water to each bay, the volume of drainage from the Barr Creek area would decrease. In this context, reduction means improving irrigation efficiency to decrease irriga tion even t runoff (runoff is no rmally at around 20-30% of supplied volume and would decrease in thi s option to around 5-10%). The monitored bay had a surface salt export ratio of 100% (i.e. salt out/salt in = 1 or

100%). WATER MAY/J UNE 1999

23


CATCHMENT

HYDROLOGY

Sallnlsed Irrigation bays

If the earlier assumption that irrigation runoff is only a minor contributor to the high regional salt export ratio is correct, a significan t redu ction in regional salt export can o nly be achieved by controlling the groundwater seepage into the deep drains, for example, by lowering the groundwater table. U nfo rtuna tely, improveme n ts in irrigation efficiency (i.e. reduction of drainage volu me from 20% to 10% of supplied irrigation volume) are unlikely

to have any im pact on groundwater elevations. During irrigation, groundwater under the monitored bay rose almost to the soil surface as irrigation wa ter infiltrated qui ckly through a network of soil cracks. While a reduction in ove rall irrigation volume decreases the amount of drainage water, it does not affect the amount of infiltration and groundwater elevations therefore remain high . In additio n , smaller irrigation events fail to remove sufficient salt from the surface soil of the bay.

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A reduction in 1rngation volumes can lead to a build-up of salt on the bay surface, particularly in th e downstream o r lower bay area. As this research showed, salt from the soil is mobilised rapidly into the surface water during the early stages of infiltration, regardless of the amount of water applied. However, this mobilised salt remains on the bay surface during low volume events, wh ile larger volumes are able to export much of this salt. These fi ndings also suggested that in order to minimise the build-up of salt in the surface soil of the irrigation bay, irrigation volumes should not be reduced to a level where the percentage of irrigation wate r that becomes drainage is less than 20%. If less water than this is applied, salt build- up on the soil surface is likely to occur in parts of th e bay whe re the mobilised salt remains after irrigation. Since small changes in irrigation bay manageme n t have little effect on regional salt export, othe r options must be considered to provide greater benefit for local irrigation bay conditions. Reu sing drainage water is o ne of these .

Reuse of Irrigation Drainage A better method to improve irrigation efficiency for water supplied and sold to the farmer bu t not reducing the amount of water used to irrigate a bay, is the on-farm reuse of drainage water. T his option allows irrigation runo ff to be collected and then pu mped when necessary to suppleme n t irrigatio n volumes . Wa ter auth ori ties ac tively encourage irrigators to adopt this manageme nt approac h due to the combined benefits of providing additional water for irrigation and for reduction in regional drainage volumes. This ena bles more efficient removal of drainage to off-stream disposal schemes . C R C for Catchm ent Hydrology research has allowed increased confidence in the on-farm benefi ts of d rainage reuse. The removal of salt from the surface soil has been shown to depend on having large 1rn gation volumes of about 20-30% of supply volume to drainage. With a reuse system, irrigators can continue to ma in tain the necessa ry volumes ofirrigation, withou t excessive contribu tion to regional drainage. O nfarm reuse offers the benefits of removing salt from the bay surface, increasing relative irrigation efficiency and reducing irrigation ru noff contribu tion to regional drainage.

Author

.::EE CALL: 008 077 744

24

WATER MAY/ JUNE 1999

FAX: (07) 3287 6445

Mat Gllfedder 1s a Proj ect Researcher with the CRC at M onash University. H e is a former C R C graduate student.


CATCHMENT

Introduction

HYDROLOGY

with th e error stru cture fo r radar data is that very large errors can be made under some circumstances. These errors can prove disastrous if they are not detected and corrected before being used in a h ydrological model which does not forgive and fo rget easily. The Bureau of M e teorology has inves ted heavily in wea th e r radar technology for applica tio ns in m eteorological forecasting and now operates a network of 50 radar stations. Since an archive of histo rical data has bee n accumulating fo r about five years, it was o pportune fo r th e Burea u of M eteorology to initiate a resea rch project to learn how to make quantitative measuremen ts of rainfall with a weather radar and to evaluate the use of these data in Australia. In O ctober 1997 the C R C fo r C atchment Hydrology began a project Spa tial Distribution of R ainfall and Storm M ovem ent (Using R em ote Sen sing) carried o u t wit hin t he H yd rology U ni t of the Burea u o f M eteorology in collaboration with the

B ureau o f M et eo rology R esearch Centre to : • d evelop a space- time m o del of rain fall suited to Australian conditio ns • provide improved design information such as temporal patterns (including the infl uence of storm movem en t) and areal reductio n fac tors • determine a strategy to best utilise radar, satellite and rain gauge observations independently and in com bination to m eet a range of ope rational hydrology applications. The projec t has been divided into fou r compone nts: two proj ec ts to establish the in frastruc t ure requi red to archive radar rainfall, and two proj ects to demonstrate the use of radar data in hydrology. The aim s are to : • establish an o ff- li ne radar rainfall archive of historical data. • develop syste ms for the real- time quantitative estimates of rainfall • use radar data to develop a space and time model of rainfall • demonstrate the use of radar data in hydrological applications thro ugh resea rch into the- optim al ingestion of radar data into 0.0 real-time fo recasting models.

The potential of weather radar to provide real- time hydrological models with timely and spatially d e tailed rainfields has been recognised fo r at least three decades. As th e technology to move large volu m es of radar data over the co mmunicatio n s ne two rk d evelops, this pote ntial i s becoming m ore apparent. The re ticen ce of hydrol ogists to adopt radar estimates of rainfall as th e data of choice fo r real- time applications can be regarded as a necessary application of the first law of walking on aeroplane w ings, which states that you sh ould not let go w ith one hand until you have grasped fi rmly onto something with the other. This d eep and well fo unded suspicion of radar data is based on th e maj or diffe rences between the errors inherent in radar and rain gauge estimates of mean areal rainfall. The errors in rain gauge estimates are related to the numbe r of gauges in the area of interest, the spatial distribution of the field being sampled , the smallscale topographical fea tures surrounding each gauge, and the wind speed over the lip of 2.0 the gauge. In general, the 4.0 measurem ent errors decrease 6.0 as the fraction of th e area 8.0 covered by rainfall increases. T his gives ri se to go od 10.0 m easurem ents in cases o f 15.0 widespread rainfall, when it 20.0 usually counts, and relatively 30.0 poor es timates when t he 40.0 rainfield is intermittent in both tim e and space. 50.0 Sources of e rror in radar m easurem ents of rainfall are legion, but in ge neral they can be classified as tho se arising from the characteristics of the radar and those ari sing from the characterismm 23.JAN-1999 23:43: 0 tics of the precipitation being Figure 1 Rainfal l map for Syd ney f lash flooding, 23 January 1999 m easured. The difficulty

Radar Rainfall Archive The aim of the radar rainfall archive projec t is to convert the historical archive of radar data into calibrated rainfall maps. While various acc umulation periods are p ossible, the basic product is expected to be h ourly rainfall de pth s at a 2 km sp atial resolution. One of the major barriers to using radar rainfall data is t he difficulty in unpacking th e raw t hreedimensional polar data off t he tapes and converting t he m in t o spatial rainfall maps. T his p roject has developed a suite of software to WATER MAY/ JUNE 1 999

25


CATCHMENT 50

-

Radar Rmlfal

HYDROLOGY CASCADE LEVELS E

40

)-y

0-

â&#x20AC;˘

multiplication by 4 independent naclom (multiplicati,..) iocr,meD.ta

9--Dec

16-Dec

23-Dec

30-Dec

6-Jan

Date 1-

Figure 2 Time series of mean areal daily rainfa ll for Darwin

manage, display an d process the rainfall maps, making it easy to display long sequences of radar data and to export maps into a simple format for inpu t into other applications. The vision fo r this p roject is to be able to place the data and data viewer onto a C D-ROM to allow easy access to the rainfall maps from a

PC. The conversion of radar reflectivity Z to rainfall intensity R is achieved though an empirical relation of the form Z = aR b, where a and b can be estimated by com paring the radar data with rain gauge data. T he daily rain gauge network is by fa r the most dense rain gauge network available. It was therefore decided to calibrate the radar by assuming a Z/R relation, calculating the daily rainfall based on radar measurements, and the n adj usting the Z/R based on comparisons with the daily rain gauge data. T he relationship is considered to be constant over the 24h our period, bu t can vary fro m day to day. An example o f the 24-hour accum ulation of rainfall which resul ted in flooding in Sydney on 23 J anuary 1999 is shown in Figure 1. An analysis of the radar data fo r these storms showed that w hile the inten sities of the sto rms were reasonably high, the flash flooding in Sydney on the day was due to storms w hich were statio nary during t heir lifetime. The spatial variabili ty, even for daily accum ulations, is clearly evident in Figure 1. It is this level of spatial detail which makes radar rainfall data attractive to hydro logists. The Letterbox radar station at Sydney is at the centre of the image. The map covers a square 256 km on a side, has a 2 km resolution, and is an accumulation of 144 images at 10-minu te intervals. Initial processing of the threedimensional radar data from D arwin, Sydney and Melbourne in to rainfall maps based on a standard Z/R relation h as been completed. Figure 2 sh ows a time series of mean areal daily rainfall from gauge and radar data averaged over a square 128 km at Berrimah radar, D arwin fo r the p eriod 9 D ecem ber 1995 to 9 January 1996. T his dem onstra tes tha t quite large differen ces 26

WATER MAY/ JUNE 1999

between gauge multiplication by and radar esti16 independent nuulom (multiplicativâ&#x20AC;˘) mates of mean iocnmenta areal rainfall can 2exist if a single calibratio n is used for all days and ma kes it necessary to estimate the ncalibration consta nts for each Figure 3 Schematic of a multifractal cascade model day. The next step in the archive project is to investigate uniform in time and space, or that it the vario us methods of combining radar varies in some very simple manner. The an d gauge da ta and to develop an scaling models of rainfall based on estimate of the accuracy of the final concepts developed for turbulence have product. Data quality control is very made it possible to produce a space important since the radar da ta has and time model of rainfall that is able several sources of contamination that to reproduce the scale dependence need to be recognised and cleaned from observed in rainfall statistics. These new models represent a major the data. Also, the radar record is quite broken, with missing periods lasting up adva nce in our ability to generate to several hours in many of the rain plau sible rainfall patterns in both space days. T his makes it necessary to evaluate and time over a range of scales and will whe ther the record fo r a day is complete enable us to generate many realisatio ns of a design storm with the same gross before any calibration attempt is made. characteristics of depth, duration and area. It will t hen be possible, for Real-time Rainfall Mapping A major program to develop the example, to route an ensemble of design systems required to make short-term storms through a spatially distributed quantitative rainfall forecas ts has been hydrological model to derive the upper and lower bounds for tl-ie peak initiated by the Bureau of Meteorology. discharge. Since quantitative rainfall estimates For the multifractal cascade models, based on weather radar are a significant the basic idea is to construct a multicompon ent of the Nowcasting Program plicative hierarchy of random numbers, (NP), it was decided that the optimum where each level in the cascade represtrategy would be for the real-ti me sents the variability o f the rainfield at mapping project to develop the radar some scale, as shown in Figure 3. In the algorith ms only, and to rely on the N P simplest case, as shown in Figure 3, to deliver these in real-time to the users. independent random n um bers (four at Work on this project is expected to start the fi rst step, 16 at the second and so in 1999 and will include the experience on) are generated, each with a mean of gained in p roducing the radar rainfall one, and a variance wh ich decreases as archive. the level in the cascade increases are generated. Design Storms The value of the field at some Realistic rainfields t hat represent location is the product of all the weights storms with a known return period are in the hierarchy above the pixel. T he required as input into design calcula- long- range spatial correlations arise tio n s for hydrological proj ects that from the fact that neighbouring pixels cover a w ide range of hydrological share common ancestors higher up the scales. The current standard practice is cascade. In our case, we have replaced to assume eithe r that the storm is the independent random weights with


CATCHMENT

HYDROLOGY

0.0 1.0

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Figure 5 Temporal correlation for Sydney, Darwin and a simulation

thunder storms in Sydney averaged Figure 4 Typical simulated instantaneous rainfield over squa res with 2, 16 and 128 km fields of correlated noise, where the de- sides and a simulation. The 2 km correlation length halves and the temporal correlations fo r the Darwin variance decreases exp onentially w ith 1998 data are less than the other two each step down the cascade. due to the high er mean advection speed The simplest method of allowing the for this case. However, these diffe rences field to develop in time is to use an become less significant for the larger auto- regressive lag one model to update spatial scales. It sh ould be noted that the each of the weights used in the cascade. detailed statistical analysis shown in The de-correlation length of the time Figure 5 is only possible with radar data. series of the mean areal rainfall averaged over the entire field is input as a param- Effect of Rainfall Estimation eter. After that, the de- correlation time Errors on Flood Forecasting is halved at each step down the cascade. T he statistical characteristics of the These models are deceptively simple, errors in estimates of mean areal rainfall but a large body of empirical evidence which are based on rain gauge networks and theoretical argument shows they are quite different from those based are the appropriate type of model for on radar rainfall measurements. It is rainfall. A typical field of instantaneous n ecessa ry therefore to develop new rainfield, or 'snapshot' output from the modelling strategies w hen moving from model is show n in Figure 4. The rain gauge to radar- based rainfall simulated domain is a square with 256 estimates. This project seeks to quantify km sides and 2 km resolution. T he the measurement errors in radar rainfall fields were generated at ten- minu te estimates and co develop strategies to intervals. mitigate their effects in real-time The next step in the research project hydrological forecast models. Once is to collect a li brary of significant sta tistical descripti ons of various rainfall events, and then to analyse their measurement e rrors have been develspatial and temporal characteristics to oped, 'true' rainfields (in this case develop a feel for the 'typical' statistical simulated fields from the space and time behaviour of rainfall. The statistics used rainfall model) will be adulterated with are the temporal and spatial correlation measurement noise and both sets o f functions over a range of scales, the rainfields will be passed through hydroratio of the standard deviation and the logical models in an effort co develop mean at the 2 km and 128 km scales, strategies chat can reduce the sensitivity and the exceedance probability distri- of real- time hydrological models to butions for mean areal rainfall over a radar errors. M easurement errors in radar range of scales. Early indications are that rainfields estimates of rainfall arise from the from convective systems tend to be temporal frequency of measuremen ts, quite similar when viewed as instan ta- the height of the measurements above neous rainfields. Differences in the the ground, the vertical profile of the correlation functions for various rainfall being sampled , and changes in accumulations can be explained by the the Z/R relation during the event. differences in the speed of t he storms Many of these errors can be minimised for each event. Figure 5 shows the through inc reased sp atial averaging. temporal correlation of two monsoonal T herefore a compromise must be found depressions over Darwin and a day of between increased spatial detail in the 2-FEB-1999 6:31: 0

100

Lag (minutes)

distributed hydrological model and increased measurement n01se m the input data.

Conclusions Research into the use of weather radar data for quantitative rainfall estimates has been carried out over the past 50 yea rs. There has also been a steady development of the weathe r radar network in Australia and substantial quantities of archived raw radar data are now available . The proj ect has developed software to manage and process the large data sets and a good stare has been made on processing the radar data archive at Darwin, Sydney and Melbourne into quantitative rainfall maps. Progress has also been made on the two demonstration proj ects: the use of radar data in real- time hydrological modelling; and the use of radar data in developing a space and time model of rainfall . Quantitative radar rainfall measurement depends on well calibra ted and maintai ned radar systems, as well as close attention to a large n umber of small details whic h accumulate to degrade the accuracy of the data. The hope for this project is that it will provide the cools necessary fo r t he hydrological community to start using radar data in a mo re quanti tative manner, thereby ensuring the necessary appreciation fo r the spatial and temporal variability of rainfall and the impact that this variability has on hydrology.

Authors Allan Seed is a Research Fellow, Phllllp Jordan is a post-graduate student and Xudong Sun is a Research Assistant with the CRC for Catchment H ydrology working at the Bureau of Me teorology. Ratnaslngham Srlkanthan (CRC Project Researcher) and Jim Elliott (CR C Project Leader) are with the Bureau of Meteorology Hydrology Unit, GPO Box 1289K, Melbourne VIC 3001. WATER MAY/JUNE 1 999

27


CATCHMENT

HYDROLOGY

TREES and a healthy watertable? Borehole measurement at Kyabram

Introduction

study this problem (Silberstein et al. , Planting of trees has been proposed 1997). The experiment was aimed at as a means of addressing problems in answering three key questions: areas with shallow saline watertables. In • to w hat extent can a plantation lower irrigation areas water i s usually added to the watertable in an irrigation area? • w hat is the li kely growth from such a the surface at a rate exceedi ng that used by the plants, to ensure that any salt that plan tation-is it economic? accumulates in the soil near the surface • will the salt accumu lation limit the as a result of evaporation and soil water growth and water uptake to the extent extraction by roots is leached below the that the wa tertable will rise aga in root zone of the crops or pasture. This underneath them and will the trees 'salt often leads to a rise in the watertable, themselves out' and die? restricting the depth of leaching. The watertable in the Shepparton Field Site In 1976, a 2.4 ha plantation of five irrigation area has risen over 20 m since agriculture began and is now within 1-3 Eucalyptus species (E. camaldulensis, E. m of the surface over much of the area botiyoides, E. grandis, E. globulus, E. (GBCMA, 1997). Irrigation areas are saligna) was established near Kyabram as generally very flat, and lateral flow is a density trial and species and provevery slow. Studies were done to estab- na nce trial (see Figure 1). The plantation was irrigated for the lish whether trees can be used in this environment to lower the watertable first six years and subsequently received and thereby improve the sustainability rainfall, with occasional overflow from of irrigation in these areas. irrigation channels. It is estimated that The idea is that a plantation of trees, the watertable was about 2 m below by using more water than is applied the surface at the time of planting to them in rainfall or irrigation, will create a subsu rface depression in the watertable and mcrease t he local hydraulic gradient, allowing saline water to ru n laterally from below surrounding paddocks. H owever, water uptake by the trees would resu lt in a concentration of salt in the root zone of the plantation, and this may have a feedback effect on tree growth and subseque nt water use. A project was established at Kyabram 111 northern Victoria to Figure 1 Plantation at Kyabram 28

WATER MAY/ JUN E 1999

(Heuperman, 1995). Tn 1982 a network of piezometers was installed in the plantation and surrounding paddocks, revealing that the plan tation had drawn down the watertable to around 4 m . A meteorological stati on approximately 500 m from the site has recorded rainfall, radiation, humidity, windru n and air and soil temperatures from 1976 until the present. In 1994, an intensive field program was commenced to quantify the effects the trees we re having on the watertable, the water use and growth of the trees and the effect the salt was having on the trees. Groundwater beneath the site now has a salinity ranging from 1,000 to 10,000 mg/L in the top 10 m, but is mostly in the range 2,000-3,000 mg/L.

Modelling The model used to simulate this experime n t was the sa m e as that described in the Trees on Hills: Better Growth = Less Waterlogging article in this issue of Water, with the addition of a finite elemen t groundwater model w hich links to the surface soil column (see Silberstein et al., 1999). A critical parameter of the model is the p lants' sensitivity to salt. This is represented in the figures by the symbol TJ • This facto r is used as a multiplier for th e osmotic potential of salt in the soil moisture and acts to limit the roots' ability t o extract water in the same way as soil moisture potential. The simulations were co ndu cted 111 three


CATCHMENT

HYDROLOGY Model Comparisons with Field Data

Model Comparisons with Field Data

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Figure 2 Comparison between field observations and model simu lations

series. The firs t was to reproduce the growth, water use and wate rtable dynamics of the plantation . The second series explored how different environm e ntal conditio n s impacted on modelled growth and water balance components. The third was a set of modelli ng experiments to predict the effects of a number of different management scenarios on the trees' growth and on pasture which would replace the plantation w hen it is harvested.

Results and Discussion Figure 2 shows the modelled performance of th e plantation alongside the measured data for the four years of intensive field monitoring. Comparison is made between field observations and model simulations of a) transpiration , b) leaf area index and c) watertable depth under the plantation during the inte n sive monitoring program. The watertable depth plotted is the average level in all piezome te rs penetrating permanently to the watertable. The dotted lines indicate estimated standard error bounds. The mean transpiration rate through the two-year measurem ent p eriod was only 1 mm/day and for the instruments used there is a measurement e rror of 30% at times. This makes it very difficult to examine the differe nces between predicted and observed water use and hence to determ ine how the model could be improved. Only through the first 150 days of measurement was there much variation and this was reproduced by the model quite well, with a coefficient of determination of 0.72. This corroborates earli er studi es which validated the same transpirati911 model at different sites with different climatic conditions (Vertessy et al., 1996; D awes et al., 1997; Zhang et al. , 1996; Zhang et al., 1999). The m easured leaf area index (LA I) shown was estimated u sing two

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Figure 3 Modelled and measured t rends of the 21-year life of the Kyabram plantation

techniques and the model resul ts fell right between them . T he differences in the seasonality between the modelled and measured LAI were partly due to attac ks by defoliating insects which occurred during this time which were not represented by the model. The figure shows a declining trend over the last four years, possibly due to the influence of salt accu mulation. The wate rtable dynamics reproduced by the model agreed closely w ith the measured watertable behaviour, although the modelled watertable had a greater seasonal variability than th e measuremen ts. The site has proved to be highly heterogeneous, as indicated by the error bounds shown for the measured trace, which is the average of all 24 piezometers in the plantation.

Measurement of downland salinity at Kyabram

For the 21-year simulation fro111 th e ti me of planting, the model was initialised with an estimate of seedling leaf area and over the last three years still produced a good comparison with the measured LAI. Figure 3 sh ows modelled and measured trends in (a) watertable depth , (b) salt storage withi n the top 8 111 of so il, (c) live stem carbon, and (d) LAI through the 21-year life of the plantation at Kyabram. The dotted lines indicate the estimated standard error bounds. T he results indicate that the model is reasonably stable and I-us represented processes in a balanced manner. Over the 21 - year life of the plantation, th e simulated watertable also follows that of the measured one, although the model suggests that it would have been drawn down to deeper levels during the period 1984-1991 w hen growth was at its best. As fa r as we can tell, the model reproduces salt accu mu lation at about th e right rate (see Figure 3). This is particularly enco uraging, since it means the model simulates the right ba lance of tree water uptake from rainfall and grou ndwater. If this balance were not correct, the observed and p redicted salt accumulation rates would differ. The average wood production across the species of the plantation is around 15 m 3/ha/yr, wh ich is a reasonable rate. The modelled live stem carbon shown, co rresponding to sapwood, shows a similar trend to the measurements (two es timates are shown) with a peak around 1984 shortly after irrigation ceased and a decline since then as the effects of a falling watertable and salt accumu lation beca me apparent. Live stem carbon multiplied by about 40 gives an estimate of sapwood volume in m 3/ha. Figure 4 shows the response of the plantation to groundwater salini ty and the trees' sensitivity to salt (11) . These have a significant effec t on plantation WATER MAY/JUN E 1999

29


CATCHMENT

HYDROLOGY

LAI for Different Groundwater Salinities

Figure 4 The effect on plantation leaf area of groundwater salinity and for three values of salt sensitivity

LAI, and on stem carbon growth shortly after irrigation ceased. The lower the salini ty in th e groundwater the greater the leaf area and stem growth , regardless of the value of ri . The connection between salt sensitivity and salt concentration is evident, for example when ri = 0.5 and TSS = 2,000 mg/L, both LAI and stem growth generally followed the tre nd of the trees over the lower salinity (TSS = 700 mg/L) groundwater. W hen ri = 0.5 and TSS = 6,000 mg/L, or w hen ri = 1 and TSS = 2,000 mg/L, there was a general decline in LAI from the time irrigation ceased. This can also be seen as a lesser ability to recover from stress, such as that imposed by the low rainfall in 1994. Figu res 5, 6 and 7 show the results from simulations in which the plantation has been 'harvested' and replaced by pasture, w hile a new plantation is establish ed in a neighbouring paddock. LAI and stem growth of the second rotatio n were slightly less than those of the first, due to the impact of salt accumulated during the first rotation period. The data are plotted for three domain elements indicating the first plantation, the site w ith the second plantation, and permanent irrigat ed pastu re. The verti cal dashed line indicates the timing of the harvest and second planting. Figures 6 and 7 are representations of watertable depth and salt accumulation through time under both plantation rotation s. They show the watertable rising up after the firs t plantation is harvested relative to su rrounding pastu re and the persisten ce of the salt accumulation. The watertable drawdown is only with.in about 30 m of the plantation. Consequently, the salt accumulation is all immediately underneath the plantation. T he rate of salt accumulation under the irrigated pasture was slower than u nder the trees, and the watertable shallower. The accumulation of salt, 30

WATER MAY/JUNE 1999

Conditions during Two 20yr Rotations

Figure 5 Environmental conditions for first and second rotation plantations at Kyabram

even under the areas which were permanently unde r irrigated pasture, indicates that t he leaching fraction applied was inadequate. A sobering result of these simulation s is that w hen the first rotati on was replaced by irrigated pasture, the new pasture was severely hampered by the salt accumulation which had occurred under the trees. As the watertable rose when irrigation recomm enced, and the salt moved upwards, the LAI of the pasture on the old pla ntati on site dropped, so that it could not survive by about the eighth year. If this is observed in the field-and the experiment ought to be donethere are severe implications for curre nt strategies recommending widespread short rotation tree plan ting in saltaffected and shallow watertable areas. Our results did not show any export of salt from under the root zone of the pasture when it replaced the first rotation, presumably because of the assumptions of the groundwater model, the low conductivity of the soil, and th e inadequate leaching fraction. Two strategies which may limit salt accumulation under the trees are to irrigate the plantation throughout its growth, or to harvest the first plantation sooner. When these were simulated (not shown here) there were modest increases in LAI and stem growth and modest reductions in salt accumulation. When the plantation was replaced by irrigated pasture, the lower salt accumulation did result in pasture survival and growth , but it was significantly lower than the permanent pasture whi ch surrounded it.

Conclusions Wood production of the Kyabram plantation has been found to be modest, but may be commercially viable. For the existing plantation, our simulation s show that the maj or benefit of a

lowered watertable occurred during the period 1985-1994, after w hich time it began to rise. T he simulation s suggested the watertable will remain at roughly its current level fo r an othe r ten years, before risi ng slightly further. Over the same period, LAI and stem growth are exp ected to decline. The results suggest that salt in the soil was signi ficant in reducing the trees' water use and growth from th e time irrigation of the trees ceased. T he low conductivity of th e¡ soil, which has resulted in the watertable being drawn down to 4 m, has mea nt that water flow to the trees was slow, adding to the diffic ulties caused by the salt in the root zone. At a site w ith a higher hydraulic conductivity, this may not be such an issue, as soil moisture may more readily be supplied to the roots and into the plantation from surrounding irrigated fields. However, this greate r water supply will also bring with it more salt, and the balance between extra growth from more water and th e negative influence of the salt accumulation may be highly dependent on occasional leaching events. We found that plantations grown over waters with lower salini ties may continue beyond 30 years, the likely rotation length. Over higher salinity groundwater, stress from salt accumulation manifests as a reduction in the ability to recover after a drought period. This was illustrated by the response after the drought in 1994-1995 , when the plantations over the higher sali nity groundwaters did not recover. The simulations showed that harvesting a plantation and returning the site to pasture m ay result in a severe reduction in pasture growth because of the salt accumulation in the soil, as it rose with the watertable. W ithin eight years the pasture could not grow. It is likely that a substan tially increased leaching fraction would be required to


CATCHMENT

HYDROLOGY Salt Store Under 1st and 2nd Rotation

Watertable Under 1st and 2nd Rotation 2nd Plantatio.:i.. ....... ···

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Figure 6 Mont hly watertable surface thro ugh time under first and second plantation rotations

redu ce this salt rise. Irrigation of the plantation and earlier harvest lessened the salt accumulation, but increased the environme ntal cost of a shallower wat ertable. Our results suggest that finding the optimal plantation rotatio n involves a balance between pasture and plantation productivity. A critical compon ent in th ese findings, w hich needs a signi fi cant amount of further work , is the sensitivity of the trees to salt and h ow that interacts w ith the so il moisture conditions in affecting growth.

Figure 7 Salt accumulation surface in time under first and seco nd plantat ion rotat ions

S, T horburn P J , Smith DJ, and Walker GR, Growth and Groundwater Uptake R esponses of Lucerne to Changes in Groundwater Levels and Salinity: Lysimeter, l sotope and Modelling Studies. Agric. Water M anage. (in press).

Authors Richard Silberstein is a Project Researche r and Rob Vert essy is D eputy Director, P rogram Leader Forest Hydrology, CRC for Catchment

H ydrology, CSIRO Land and Water, GPO Box 1666 , Canbe rra ACT 2601. Jim Morris is a R esearch Scientist, CRC for Catchment H ydrol ogy, Centre fo r Forest T ree Technology, H eidelb erg, Victoria and Department of Natural Reso urces & Environment. Paul Felkema is a Research Scientist wi th the Centre fo r Fores t Tree T echnology, D epartment of Natural R esources and Environment and a former CRC gradu_ate student.

References GBCMA, (1997) Shepparcon Region Watertable Contour Map, August (1997) The Goulbum-Broken Catchment Management Authority, Shepparton and North Central Catchment Management Authority, Bendigo, Victoria. Silberstein RP, Vertessy RA , Morris J and Connell L D (1997) Predicting the Water and Salt Dynamics Beneath Plantations. Watcr24(1): 10. Silberstein R P, Vertessy R A, Morris J and Con nell L D (1999) Modelling the Effects of Soil Moisture and Solute Conditions on Long-tenn Tree Growth and Water Use: A Case Study from the Shepparton Irrigation Area, Australia. Agric. Water Manage. (in press). Vertessy R A, Benyon R G , O'Sullivan S K and Gribben P R (1995) R elationships Between Stem D iameter, Sapwood Area, Leaf Area and T ranspiration in a Young Mountain Ash Forest. Tree Physiology, 15: 559-567. Vertessy R A, H atton T J , Reece P, O'Sullivan S K and Benyon R G (1996) Long- term Grow th and Water Balance Predictions for a Mountain Ash (Eucalyptus regnans) Forest Catchment Subject to C lear- fe ll ing and R egeneration: Tree Physiology 16: 221-232. Zhang L, Dawes W Rand Hatton T J (1996) Modelling Hydrologic Processes Using a Biophysical Based Model: Application of WAVES to FIFE and HAPEXMOB lLHY. j. Hydro/. 185, 147- 169. Zhang L, Dawes W R, Slavich P G, Meyer W

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CATCHMENT

Satisfying the thirst for better tools and knowledge

HYDROLOGY

TECHNOLOGY

D Perry

The term 'techn ology transfer' m ea n s diffe rent thi ngs to differen t people. It can be defined very narrowly as the direct application of techn ology from o ne situation to another, o r it can be u sed m ore broadly to include elem ents of adult edu cation , comm unication , extension and actio n resea rch. H owever one describes it, the principles of technology transfer are a focus of the C RC for Catchment H ydrology. Our C R C i s faced w ith th e challenge-and indeed responsibili tyof transferring our research results to industry in the shortest possible time. To this end, we direct 25% of our annua l budge t to supporting our technol ogy tran sfer program. T ec hnology transfer is b uilt into the research projects from day one through regular interactions with indu stry to identi fy indu stry needs an d develop relevan t resea rch prio ri ties and products. Each C R C research proj ect requires a unique approach to d eli vering its outcomes to industry i n a fo rm that can be applied. Som e proj ects have a clearly defi ned but relatively sm all gro up of users. Othe rs have a critical communicatio n medium tha t can be targeted to ac hieve indu stry adoption such as a policy document or code of p rac tice that defines accepted industry practice. T he current revisio n of the industry standard Australian Rain fall and Runoff (ARR) is a good example of this. The revision of chapter 13 of ARR on es timation of large and extre me floods w ill incorporate the significant adva nces made by the CRC in its Flood H ydrology program. Imple me nta tion of CRC research outcom es will then follow from the industry adoption o f the me thodology in ARR. B oth th e engineering profession and th e Australian public get their benefit from the C R C's research in this way. Similarly, in a j oint proj ect with the N ational Climate C entre, the CRC and the Bureau of Me teorology are publishing Australia-w ide potential and evapotranspiration m aps u sing Mo rton's co mpli me n tary relationship . T h ese maps provide more accurate info rm a32

WATER M AY/JUNE 1999

CRC field day at Croppers Creek, north-east Victoria

tion fo r wate r resource manage ment and studies, and will mee t th e needs of a wide range of users. O th er CRC proj ec ts have mu ch broader and diverse user groups, and require man y d iffe ren t forms o f com m uni catio n and support to catalyse th e t ran sfer of C R C tec hnology. Proj ec t outcomes in the waterway m anagem ent and fo rest hydrology program s, fo r example, have direct relevan ce to natural resou rce managers all over Australia including state agency m anage me n t and po li cy staff and Landcare and catchmen t groups. T he Land and Water R esources R esearc h and Development Corporati on (LWRRDC) and the C R C have j oin tly published the Australian M anual o f Stream R eh abilitation w hi ch can be dow nloaded from www.lw rrdc.go v.au. The ma nual , w hich relied h eavily o n the C RC' s W aterway Managem ent program , incorporates CR C and oth er research results as well as recent advances in the understanding of ecological rehabilitation. The manual aims to support stream managers around Australia by providing a decision support and prioritysetting framework fo r river rehabilitation works. Similarly, th e recent revision of the Poll ution C ontrol Licence conditions governing fo rest ope rations in N ew South W ales incorporated the improved understanding of sediment movement in forests ari sing from the C R C's Forest H ydrology program. Clearly, th e planning and implem entation of each CRC proj ect must take into account the needs, skills and capacity fo r c hange of the u sers of our

research . There is a wide variety of ways to learn about and be involved in the C R C's research and¡its outco mes. An importan t part of getting research results from proj ects to industry and o ther researchers is through our technical reports w hich detail the technical outcom es of all ou r resea rch proj ects. O ur industry reports se ries allow land and wa ter managers to quickly deternu ne the key appli cations and implication s of the C RC 's research. These nine publications are written in plain E nglish and are well ill ustra ted with diagrams and photos. Our mo nthly newsle tter Catchword is posted free to more than 1,100 people and p rovides updates on the progress and outcomes of our research . D etails of C R C pu blicatio n s and video s and upcoming senunars and workshops are also given. Co ntact Virginia Verrelli on tel. (03) 9905 2704 or email: virginia. verrelli@eng.monash .edu.au to be put on the mailing list. Arou nd 30 technical senu nars are held each year and presenters usually focus on a specific issue o r area of researc h an d often include gen eral implica tion s of the research outcomes to date fo r the land and water management indu stry. The speakers provide de tailed information about the research techniques, analysis and results. They are delivered in most capital cities with a regular program given in M elbourne and Canberra. There is no charge for participants. A se ries of industry seminars for land and wa ter managers aims to bridge the traditional gap be tween research ou tcomes and industry practice and deliver CRC research outcomes in a


CATCHMENT

HYDROLOGY

Industry reports

Seminar videos

Technical reports

practical, real world and integrated co ntext. Speakers at each seminar include staff from the land and water management industry, the CRC for Catchment H ydrology and collaborating research organisations. Industry seminars have attracted large audiences, which we are able to extend by repeating them in other capital cities. We produce professional video tapes of our industry seminars and of selected technical seminars. All are available through the AWWA Bookshop and the CRC Centre Office. The videos allow people who can't attend a seminar to view the presentation and keep informed of the CRC's research progress and results. Details of all the CRC's videos and reports are provided in the quarterly CRC Publications List, available free

from the CRC Centre Office. A stro ng interaction between research and industry staff is encouraged by field tours which are generally held over one or more days. These involve a tour of specific sites of interest where the results of CRC research in understanding land and water management issues can be discussed in practical terms. CRC workshops provide an opportunity for on the spot discussions between CRC researchers and industry staff and often include a strong training element. Keeping abreast of field tours and workshops held by the CRC is easiest through Catchword or regular visits to our website. T he website (www.catchment. crc. org.au) provides details of completed and current projects, contact details for

CRC staff, products and seminars. Catchword is posted each month on the websi te, w hich is also h ome to TOPOG , a sophisticated catchment model used to predict the water, solute and carbon balance of catchments. TOPOG can be applied to water yield, salinity management and effluent disposal issues. Currently over 200 users around the world have downloaded TOPOG from the CRC website. Over the next 12 months we w ill continue to expand our website utility to provide a range of information and tools for education and application.

Author David Perry is Technology Transfer Coordinator, CRC for Catchment Hydrology, email david.perry@eng. monash.edu. au.

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Abstract The nature an d concentration of dissolved o rganic matter (DOM) impacts b oth on the treatability of water for drinking purposes and on the formation of disinfection byproducts. This article is a review of the origin and tran sformation processes of the natural organic matter (NO M ) in wa te r resources.

Key Words NOM, natural organic matter 111 water, transport of NOM, transformation ofNOM

Introduction One of the major costs of treating water for drinking purposes is tha t associated w ith the removal of the natural organic matter (NOM). The particulate fraction of NOM (POM) is generally easily removed by the flocculation and fil tration processes. H owever, the dissolved fraction of the NOM (DOM) and the characteristics of DOM directly impact on the treatability of the water (Owen et al., 1995; Randtke, 1993). Improving understanding of the significa nt fac tors controlling the o rigin of DOM in a reservoir is imnortant to water authorities trying to opti mise catchment management to minimise water treatment costs.

Nature of NOM NOM is the co nglo m eration of organic chemical byproducts of living and decaying plant and animal matter and is present in all natural waters. The fac tors controlling the range and types of chemical and structural characteristics of the moieties w ithin a sample of NOM are the origin of the organic matter, the degradation to w hich it has been subjected and th e physical and ch emical environments with w hich it has come into contact. NOM is a complex mix ture of organic chemicals which , due to the immense variability in molecular size and structure, is diffic ult to characterise using traditional analytical m e thods (R e uter and Perdue, 198 1; P erdue, 1985; Stevenson, 1994 and Chen et al. , 1977; W ilson et al. , 1983; Steven son , 1994; H ayes et al. , 1989; Swift, 1996 respectively) . The NOM in reservoir water, the raw wate r used in water treatment, contains a mixture of NOM fro m various water sources in the catchment, transported via above-ground o r underground paths. The nature of the NOM is u nique for each sample of water and is changing co nstantly. C hanges can occur during the transport process, in the soil,

stream or reservoir enviromnent, and are generally associated with four main types of processes-microbial, chemical, physical and photoche mical. Therefore, the characteristics of the organic matter present in raw water samples is the culmina tion of innume rable changes along the transport path and in the water column. A survey of recent literature gives an ove rvi ew o f the present state of understanding of the origin and character of D OM in reservoirs.

Transformation of NOM A reservoir has a defined catchment source and the nature of the catchment (physical shap e and size, geograp hic location, rainfall events etc.) will impact on the quantity and nature of the DOM transported to the reservoir. Phillips and Bachman (1996) used principal component analysis to determine two main types of catchment areas or basins: '(1) well-drained basins, characterized by combinations of a low percentage of forest cover, low percentage of poorly drained soil, and elevated channel slope; and (2) poorly drained basins, characterized by a combination of an elevated perce n tage of forest cover, an elevated percentage of poorly drained soil , and low channel slopes.' They found that the water chemistry of the two differed significantly, with concentrations of DOM elevated in the

poorly drained basins. Similar results relating runoff water inversely to the concentration of DOM in streams have been found by Newbold et al. (1995) and for NOM released from flooded soils (Wang and Bettany, 1995). It has also been shown that the concentrations of nitrate and dissolved phosphorus (important in microbial processes) are inversely related to the annual runoff (Newbold et al., 1995). Vegetation growing along streams and reservoirs plays an important role in the quality and quantity ofNOM entering these water systems, both by direct input (types of decay products.) and as a retention structure. The efficiency of retention stru ctures such as roots, branches and boulders depends on the water level and discharge (Maridet et al. , 1995). Most of the NOM entering these water systems is in the coarse particulate form, although most of the export is in the fo rm of fine POM, DOM and respired CO2 and is mu ch lower than the input (Wallace et al., 1995 ; M cC art et al. , 1995). Wate r flow and NOM input to reservoirs also occur via underground flow paths. W here the 'released NOM is not significantly different from one soil to another on a quantitative basis, its quality seems to be linked to the soil type, the former water content of the soil and the intensity and duration of storms' (Boissier and Fontvieille, 1995). The extent of sorption of D OM by colloidal minerals in the soil or water WATER MAY/JUNE 1999

35


WATER environment will be associated with the surface area of the soil particles, the nature of the soil minerals, pH and the nature and concen tration of the background solu tion el ectrolyte (Tipping and Woof, 1991; Nelson et al., 1993; Spark et al., 1997 a, b; Kaiser and Zech, 1997). Studies of the transported DOM through the soil horizon have shown that the nature of DOM changes significantly w ith seasonal changes, indicating that the microbial processes are im portant (Spark et al. , 1998). T he active microbial biomass, as a fraction of the total soil microbial biomass, increases with increasing depth and was more active in the lighter frac tion (density less than or equal to 1.6 g rnl-1) of the soil (Alvarez et al., 1998). T he types of microbial processes depend on the environmental conditions and may be responsible for considerable DOM removal before it reaches the reservoir (Fiebig, 1995; Findlay et al. , 1996).

NOM in Reservoirs As reservoirs are not closed water systems, the source of the organic matter i s a combinati on of bo th au toch th onous and allochthonous organic matter. T h e relative significance of these two types of genesis on the overall cha racteristics of the organic matter in the reservoir is not very well understood. T he chemistry o f th e lower depths of a reservoir is also an important aspect of the overall natu re of the DOM in reservoirs. The types of in teracti ons in which the DOM is involved with the sedimentary layers and lowe r wate r levels depends on a number of factors including residence times, the physical

NOM, and determine which parameters affect the nature of the NOM (whether in soil, sediment or water) and the relative significance of the effects for each parameter. Of particular interest to the water industry i s how these processes affect the partitioning of the NOM into the particulate or dissolved state (POM or DOM) and hence the factors controlling the character of the DOM. In general, the four main types of processes which change the character of NOM and the partitioning between POM and D OM are chemical, physical, microbial and photoch emical. Chemical Processes T he chemical processes affecting the character of the NOM are changes in pH , solution electrolyte concentration, D OM concentration and temperature. C hemical changes can involve both the formatio n and breakdown of chemical bonds and can also influence partitioning of the NOM between POM and DOM. This process is possibly not significant in isola tion due to the relatively mild chemical co nditions in the natural environment in most situations. POM - chemical +- DOM

Physical Processes Interactions with minerals can occur for a number of reasons including electrostatic interactions, van der Waals fo rces o r chemical in teractions with the surface of the minerals (or the organic matter coating these minerals). The interaction affects the su rface potential of the mineral as well as its surface chemistry (Wilkinson et al. , 1997). Fabris and Spark (1998) have shown that silica adsorbs very li ttle DOM, whereas goethite, 'Of particular interest to the water industry the strongest adsorbent of t he four is how these catchment processes affect the minerals studied, showed li ttle precharacter of the DOM.' fere nce fo r any particular functional shape of the reservoir storage basin and group generally. D OM adsorption by th e temperature and volume of the kaolinite and alumina exhibited preferlower level (Tietj en et al. , 1995). D ue ences for particular types of fu nctional to the short residence times of water in groups (carboxyl groups are adsorbed in reservoirs gen erally (compa red with preference to amide/amine and phenolake systems), the quantity and quality lic groups) . From th ese results it wou ld be of NOM transported to a reservoir would be of significant im portance to expected that the nature of the minerals with which a sample of DOM comes the fi nal character of the NOM. It is virtually impossible to iden tify, into contact can influence the characor even comprehend, the number and teristics of the transported D OM in a nature of processes w hich a sample of soil environment. It may therefore NOM has undergone in a catchment, affect the characteristics of the D OM from all its myriad sources and transport being transported into streams and paths, to make up the sample of raw reservoirs. Simila r resu lts have been water to be treated for drinking found by Kaiser and Zech (1997). purposes. Instead it would be simpler to It has been reported that the co ncentrate on t he main types of hydrophobic and hydrophilic fractions p rocesses that change the nature of the of D O M have different adso rption 36

WATER MAY/JUNE 19 99

properties with soils, with the hydrophobic fraction being preferentially adsorbed (Gu et al., 1994, Kaiser and Zech, 1997). T his fraction is possibly being adsorbed by the particulate organic matter in the soil w hich is insoluble due to its hydrophobic character. POM +- +- +- mineral - DOM Microbial Processes There is evidence to suggest that the bacteria utilise the DOM fraction in prefe rence to t he POM fractio n (Middelboe an d Sondegaard, 1995). H owever, they are strongly associated with the POM frac tion (Amon and Benner, 1996). The main componen ts of D OM utilised by bacteria are carbohydrates, with protein-derived compou n ds showing co nsi derable importance as well (Michard et al. , 1995 ; Tranvik and J orgensen, 1995; H anisch et al., 1996; Striquer arid C hevolot, 1996). T he principal photosynthetic endproducts of phytoplankton processes are polysaccharides followed by proteins, low- molecular-weight compounds and lipids (Maurin et al. , 1995). Maurin et al. (1995) showed that nitrogen, phosphorus and temp erature were all imp o rtant components in bacterial metabolism, with simila r findings fou nd by others for fungi metabolism (Suberkropp and C hauvet, 1995). In some instances p hosphorus has been me n tioned as often being the li miting nutri ent fo r these types of processes (Takashi et al. , 199 5; H ellstroem, 1996), whereas in others the microbial process is more strongly correlated to the nitrate concentration (Suberkropp and Chauvet, 1995) . Fluctuations in t he overall concentration of DOM have been directly related to growth periods in bacteria (Sondegaard et al., 1995) with around 10% of the combined fluxes of DOM and POM in natural waters estrmated to be converted into CO 2 (Dawson et al., 1995). POM +- microbial - DOM Photochemical Processes The effect of sunlight on the upper layers of natural waters converts the h igh-molecular-weigh t D OM to a more aliphatic character with a correspo nding increase in carboxyl and carbonyl functional groups (Kulovaare et al. , 1996). In the upper surface layers in these systems the rate of photochemical consumption of DOM has been shown to be m uch greater than that consumed microbially. H owever, in the overall water column the microbial process was fou nd to be mo re important, possibly because the microb ial process does n ot significantly depend on the presence o f light (Amon and Benner, 1996). In general, t he


WATER longer the residence time the lighter the colour of the DOM in reservoirs, indicating a larger photodegradation of the DOM (Townsend et al., 1996). IDM +- light + + + OOM +- light + + -+ CO) In general, reservoir waters have J maximum amount of carbohydrate in the summer when DOM, aliphatic C and carboxylic C are at a minimum, with the latter three being at a 1naximum in the autumn and winter months. In a study by Clair et al. (1996) it was found that the aromatic component of the DOM (as determined by solid state 13 C Nuclear Magnetic Resonance) remained at less than 10% of the total C and was thought to be refractory. Other important groups of organic chemicals found in freshwater systems are aliphatic hydrocarbons, ketones, alcohols, triterpenoids and fatty acids, of which a large proportion are autochthonous in origin (Jaffe at al., 1995). This review verifies the need to view reservoir systems as open systems and acknowledge that catchment factors are important to the nature of the DOM in reservoirs.

Conclusion Categorising the myriad of processes concerning DOM in a catchment into four types as shown above greatly sitnplifies the overall view of the system. By choosing appropriate and sufficient parameters for each of these four processes to account for the significant interactions in the catchment, and by using DOM/NOM in studies from a variety of sources, it may be possible to i1nprove understanding of the relationship between the origin and character of DOM and problems associated with its treatability. This approach is the basis of much of the research work being carried out on the character ofNOM in Program 2 (Catchment Management) of the Cooperative Research Centre for Water Quality and Treatment. One project has used Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFT) to analyse the functional groups of DOM. This technique has been applied not only to the water in reservoirs but also to the leaf litter, soils and sediments encountered by the water on its way to the reservoir (Spark, 1998). In the DOM extracted from leaf litter, the dominant groups were the initial breakdown products of vegetable matter, i.e. cellulose and lignin compounds such as alkyl, carboxylate and aliphatic-O groups. Samples taken from a slow-flowing stream at the base of a catchment slope indicate the effects of adsorption on soil particles, as well as microbial activity. Carboxylates, being negatively charged, were preferentially adsorbed. Protein-

aceous matter was broken down to polypeptides and amides. In the reservoir, the dominant groups were the soluble refractory endproducts of the various processes. Phenol and quinone groups derive from breakdown of aromatic organic matter, whereas amides and esters are the more stable derivatives of carboxylates. Although polar, and therefore soluble, the absence of charge on these groups explains why they have not been readily adsorbed by soils and colloidal particles, and also why they are difficult to remove by the coagulative treatment processes.

References Alvarez C R, Alvarez R, Grigera S and Lavado RS (1998) Associations Between Organic Matter Fractions and the Active Soil Microbial Biomass. Soil Biology and Biochcmist1y. Vol. 30, No. 6, pp.

767-773. Amon R M W, Benner R (1996) Photochemical and Microbial Consumption of Dissolved Organic Carbon and Dissolved O:-.)'gen in the Amazon River System. Gcochim. Cosmochim.

Act.1Vol. 60, No.10, pp.1783-1792.

Boissier J M, Fontvieille D (1995) Biological Characteristics of Forest Soils and Seepage Waters During Simulated Rainfalls of High Intensity. Soil Biol. Biochcm. Vol. 27, No. 2, pp. 139-145. Chen Y, Sencsi N and Schnitzer M (1977) Information Provided on Humic Substances By E.iJE6 Ratios, Soil Sci. Soc.

Am.]., Vol. 41, pp. 352-358.

Clair TA, Sayer BG, Kramer JR, Eaton DR (1996) Seasonal Variation in the Composition of Aquatic Organic Matter in Some Nova Scotian Brownwaters: A Nuclear Magnetic Resonance Approach. Hydrobiologi,1 Vol. 317, No. 2, pp.

141-150. Dawson J JC, Hope D, Crcsscr MS, Billett MF (1995) Downstream Changes in Free Carbon Dioxide in an Upland Catchment From Northeastern Scotland. j. Environ. Qua/. Vol. 24, No. 4, pp.

699-706. Fabris R. B and Spark KM (1998) The Effect of the Soil Environmental Factors on the Nature of the Dissolved Organic Matter. Conference Proceedings (CD-ROM), 14th World Congress of Soil Science, Symposium 7, Montpellicr, France, 22-26 August 1988. Fiebig D M (1995) Groundwater Discharge and its Contribution of Dissolved Organic Carbon to an Upland Stream. Arch. Hydrobiol. Vol. 134, No. 2, pp.

129-155. Findlay S, Sobczak WV (1996) Variability in Removal of Dissolved Organic Carbon in Hyporheic Sediments. J. N. Am. Benthol. Soc. Vol. 15, No. 1, pp. 35-41. Gu B, Schmitt J, Chen Z, Liang L and

McCarthy J F (1994) Adsorption and Desorption of Natural Organic Matter on Iron Oxide: Mechanisms and Models Environ. Sci. Tcclmol. Vol. 28, pp.

38-46. Hanisch K, Schweitzer B, Simon M (1996)

Use of Dissolved Carbohydrates by Planktonic Bacteria in A Mesotrophic Lake. Microb. Ecol. Vol. 31, No. 1, pp.

41-55. Hayes M H B, MacCarthy P, Malcolm Rand Swift RS (1989) Humic Substances JI: In Sc,1rch of Strucwrc, Wilcy-Interscience, Chichester. Hcllstrocm T (1996) An Empirical Study of Nitrogen Dynamics In Lakes. Water Environ. Res. Vol. 68, No. 1, pp. 55-65.

Jaffe R, WolffG A, Cabrera AC, Chitty H C (1995) The Biogeochemistry of Lipids in Rivers of the Orinoco Basin. Geochim. Cosmochim. Acta Vol. 59, No. 21, pp.

4507-4522. Kaiser K and Zech W (1997) Competitive Sorption of Dissolved Organic Matter Fractions to Soils and Related Mineral Phases, Soil Sci. Soc. Am.]. Vol. 61 pp.

64-69. Kulovaara M, Corin N, Backlund P, Tervo J (1996) Impact of UV254 Radiation on Aquatic Humic Substances. Chcmospherc Vol. 33, No. 5, pp. 783-790. Maridet L, Wasson] G, Philippe M, Amoros C (1995) Benthic Organic Matter Dynamics in Three Streams: Riparian Vegetation Or Bed Morphology Control? Arch. Hydrobiol. Vol. 132, No.

4, pp. 415-425. Maurin N, Amblard C, Bourdier G (1995) Vertical and Seasonal Variations of Inorganic Carbon Allocation into Macromolecules by Phytoplankton Population in A Brown-Colored and A Clear-Water Lake. Space Partition Within Aquatic Ecosystems. Balvay G

(Ed.) pp. 57-70. McCart R E, Gordon A M, Kaushik N K, Lazerte B, Mallory E, Bachmann R W, Jones] R, Peters R. H, Soballc D M (Eds.) (1995) Characterization of Selected Allochthonous Organic Carbon Inputs Within A Terrestrial-Aquatic Ecotone in Algonquin Park, Ontario. Lake Rcscrv. Man.1gc. Vol. 11, No. 2, p. 168. Michard M, Aleya L, Devaux J (1995) Diel Changes in the Biochemical Composition of the Particulate Matter Coupled with Several Parameters in the Hypereutrophic Villerest Reservoir (Roanne, France). Space Partition Within Aquatic Ecosystems. Balvay, G. (Ed.) pp. 85-91.

Middclboe M, Sondergaard M (1995 ) Concentration and Bacterial Utilization of Sub-Micron Particles and Dissolved Organic Carbon in Lakes and A Coastal Arca. Arch. Hydrobiol. Vol. 133, No. 2,

pp. 129-147. Nelson P N, Baldock J A and Oades J M (1993) Concentration and Composition of Dissolved Organic Carbon in Streams in Relation to Catchment Soil Properties Biogcochcm. Vol.19, pp. 27-50. Newbold J D, Sweeney B W, Jackson J K, Kaplan L A (1995) Concentrations and Export of Solutes From Six Mountain Streams. In Northwestern Costa Rica.]. N. Am. Bcnthol. Soc. Vol. 14, No. 1, pp.

21-37. Owen D M, Amy G L, Chowdhury Z K, Paode R, McCoy G and Viscosil K (1995) NOM Characterisation and Treat-

ability j. A WWA Vol. 87, no 1, pp. 46-63. Perdue EM (1985) Acidic Functional Groups of Humic Substances. In G R Aiken, D

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WATER M McKnight, R L Wershaw and P MacCarthy (Eds.) Humic Substances In Soil, Sediment and Water. Geochemistry, Isolation and Characterisation. W ilcylnterscience, New York, pp. 493-526. Phillips P J , Bachman L J (1996) Hydrologic Landscapes on the Delmarva Peninsula Part 1: Drainage Basin Type and BaseFlow Chemistry. Water R esour. Bull. Vol. 32, No. 4, pp. 767-778. Randkte S J D (1993) Transformation of NOM During Treatment. In natural organic matter In Drinking Water. O rigin, C haracterization and R emoval Workshop Proc. pp.155- 63. C hamonix, France. AWW A Res. Found. & AWWA. Reuter J H and Perdue E M (198 1) Calculation of Molecular Weights of H umic Substances From Colligative Data: Application To Aquatic Humus and Its Molecular Size Fractions, Geochim. Cosmochim. Acta. Vol. 45, pp. 2017- 2022. Sondergaard M, Hansen B, Markager S (1995) Dynamics of Dissolved Organic Carbon Lability In A Eutrophic Lake. Linmol. Oceanogr. 1995 Vol. 40, No . 1, pp. 46-54. Space Partition Within Aquatic Ecosystems. Balvay G . (Ed.) pp. 85-9. Spark K M , Wells J D and Johnson B B (1997a) . Characteristics of the Sorption of Hurnic Acid By Soil Minerals. Australian Journal of Soil R esearch. Vol. 35, pp. 103-112. Spark K M , Wells J D and Jo hnson B B (1997b) Sorption of Heavy Metals by Mineral-Humic Acid Substrates. Australian J ournal of Soil R esearch. Vol. 35, pp. 113-122. Spark K M , Stevens D P, Cox J W and C hittleborough DJ (1998) The Effect of Transport Path on the Nature of Soluble Organi c Matter in Soil Leachates. Conference Proceedings, ASSS I N ational Soils Confe rence. Brisbane, Australia, pp. 361-368. Stevenson F J (1994) Humus Chemistry.

Genesis, Composition, R eactions, 2nd Edition. Wiley, New York. Striquer Soares F, Chevolot L (1996) Particulate and Dissolved Carbohydrates and Proteins in Lobo Reservoir (Sao Paulo State, Brazil): Relationships With Phytoplankton.). Plankton Res. Vol. 18, No. 4,pp. 521-537. Suberkropp K, C hauvet E (1995) R egulation of Leaf Breakdown by Fungi In Streams: Influences of Water C hemistry. Ecology Vol. 76, N o. 5, pp. 1433-1445. Swift R S (1996) Organic Matter C haracterization. In D Sparks, M ethods of Soil Analysis: Part 2 Chemical and Microbial Properties. C h. 35. ASA-SSSA, Madison. Takahashi M , Hama T, Matsunaga K, Handa N (J 995) Photosynthetic Organic Carbo n Production and Respiratory Organic Carbon Consumptio n in the Trophogenic Layer of Lake Biwa. J. Plankton R es. Vol. 17 , No. 5, pp. 1017-1025. Tietjen T E, Groeger A W, Guaj ardo J , Hannan H H, Bachmann R W, Jones J R , Peters RH, Soballe D M (Eds.) (1995) Predicting Patterns of Dissolved Oxygen Depiction in R eservoirs. Lake Reserv. Manage. Vol. 11, N o. 2, p. 197. Tipping E and Woof C (1991) Th e Distribution of Humic Substances Between the Solid and Aqueous Phases of Acid Organic Soils: A Description Based on Humic Heterogeneity and ChargeDependent Sorption Equilibria. journal ofSoil Science. Vol. 42, pp. 437-48. Townsend SA, Luong Van] T, Boland KT (1996) Retention T ime As A Primary D eterm inant of Colo ur and Light Attenuation in Two Tropical Australian Reservoirs. Frcsh wat. Biol. Vol. 36, No. 1, pp. 57-69. T ranvik L J , J orgensen N O G (1995) Colloidal and Dissolved Organic Matter In Lake W ater: Carbohydrate and Amino Acid Composition, and Ability T o Support Bacterial Growth . Biogeo-

BOOKS Microbial Health Hazards Associated with Effluent Reuse F Rynne and P Dart, Urban Water Research Association of Australia, UWRAA Report No. 144, ISBN 187-6088-47-8, $60 Microbial H ealth H azards A ssociated with Effluent R euse provides detail on pathogens found in effluent and those which pose the greatest h ealth ri sk in the developed world (i.e. viruses, protozoans). T he relevance of current guidelines and mi crobial quality of efflu ent are also provided, including the resul ts of a survey on pathogen concentration in Queenslan d effluents and current re use p ractices. Within the scope of this report, Quantitative Microbial Risk Assessment is used to calculate the risk of 38

WATER MAY/J UNE 1999

infection to th e public from efflu ent reu se as affected by pathogen type, concentration, application method and public knowledge. T he results demonstrate the current p oor microbiological qu ality of most sewage efflu e nt , togethe r with the almost unive rsal disregard for reuse guidelines, culminates in an unacceptably high level of human health ri sk. A semi quantitative decision tree is also included, allowing effluent reusers to gauge the relative risk of their reuse practices. T h e report provides valuable insight into the h ealth issu es involved in recycled water use and are an essential read for anyone involved or planning reuse schemes. Nicole Diatloff Centre for Integrated Resource Management University of Queensland

chemistry Vol. 30, No . 2, pp. 77-97. WaLlace J B, Whiles M R, Eggert S, C uffuey T F, Lugthart G J, C hung K (1995) Long-Term Dynami cs of Coarse Particulate Organic M atter in T hree Appalachian Mountain Streams. J. N. Am. Benthol. Soc. Vol. 14, No. 2, pp. 217-232. Wang F L, Bettany J R (1995) Carbon and Nitrogen Losses from Undisturbed Soil Colu mns Under Short-T erm Flooding Conditions. Can.). Soil Sci. Vol. 75, No. 3, pp. 333-341. Wilkinson KJ, NegrcJ CandBuilleJ (1997) Coagulation of Co lloidal Material in Surface Waters: The Role of Natural Organic Matter. J. Contaminan t Hydrology. Vol. 26, No. 1-4, pp. 229-243. Wilson M A, Gillam A H and Collins P J (1983) Analysis of the Structure of Dissolved Humic Substances and their Phytoplankton Precursors By 1H and l3C Nuclear Magnetic Resonance, Chem. Geol. Vol. 40, pp. 187-201.

Author Dr Kaye Spark is Project Leader, Program 2 (Catchment Management), Cooperative Research Centre for Water Quality and Treatment and the Australian Coordinator of the International Humic Substances Society. H er previous resea rch experie nce in this area includes the effect of NOM on pesticide tran spo rt in soils and the effect of NOM on t he interacti on of heavy me tals wi th soil minerals.

CORRECTION Dr Martha Sinclair, Editor of the Cooperative R esea rch Centre fo r Water Quality and Treatmen t's newsletter H ealth Stream, has p ointed out so me e rrors in Bob Swinton's report o f th e Cryptosporidium confe rence held in Melbourne last year ( Water, J anuary/ February, page 8). H e reported incorrectly that the double-blind point-ofuse m embrane-filtration trials were b eing held in N ew Zealand, as well as in Australia. D r Sinclair said, 'The trials in New Zealand, as well as in Australia, are case control studies, in which we interview people with labdiagno sed Cryp tosporidium in their stools, and compare them with healthy people selec ted at random. Our study 111 Melbourne and Adelaide is in the early stages. The New Zealanders have nearly finished theirs. We are currently advising the Americans on a pilot filtration trial in California. ' A furthe r co rrection pertains to the influence of animals which was discussed by Martyn Kirk of the Victorian D epartment of H ealth, not Martin Baker as published.


WASTEWATER

g

EFFLUENT

Modelling sustainable loading rates

IRRIGATION

XHu Abstract Efiluent irrigation has been recommended as the fi rst choice for efiluen t disposal by Australian governments. Many local au tho rities suc h as Thuringowa and Townsville Ciry Councils are now investiga ting the possibility of irrigating 100% of their effiuent. A computer program called Computer-aided Design of Effl u ent Irrigation (CAD-Efiluent) was applied. It was found that if cu rrent guidelines for eilluent irrigation are used for calculating the loading rate, nutrients are the limiting factors in Townsville. If the nutrient limiting factors can be reduced, the goal of reusing 100% effluent in an urban area may become more practical. The com puter investigation was covered 29 towns in Queensland and two in other states.

IN QUEENSLAND

recorded in Hawaii (Smith et al. , 1981). To min imise the environmental pollution potential from efflu ent discharge, effluent irrigation has been identified as an attractive alternative. The Queensland Department of Natural R eso urces is encouraging all eÂŁIluent generators to use efiluen t for irrigation to a maximum level. Th is includes both urban and rural industri es. Many local authorities such as Townsville and Thuringowa C ity Cou nci ls are developing and implementing plans fo r 100% effl uent reuse for irrigation. However, effi uent irrigation has problems and proper design Introduction and operation are required to make The coastal location of m ost systems sustainable in the Jong term . Queensland cities implies protection of The critical step of eilluent irrigation the marine environment. Although it is design is to determine the sustainable reported that only 2% ni trogen and 8% efflue n t loading rate. The gu idelines produced by the ' .â&#x20AC;˘. a detailed investigation of soil Queensland Department o f Natural Resources phosphorus adsorption capacity recommend that the u trient loading should should be undertaken before an nnot exceed the plant effluent irrigation system is requirement of the irrigati on system (Beavers, installed in Queensland.' 1996). An ea rly study has shown that the sustainable ph osphorus of the total nu trient input efiluent loading is controlled by nutrito the cen tral Great Barrier R eef is ents, not water, in most Q ueensland contributed by the discharge of sewage locations. effluent, significa n t local problem s This paper investigates the limiting cau sed by effluent discharge have been factors of effluent loading rate based on identified and off the Sunsh ine Coast a the recommendations of th e guidelines, change in the marine algal community and the potential to relieve the li miting has also been observed (Cosser, 1997) . condi tions. O nly the macro-nutrients The lo ng-term degradation of a reef as a -nitrogen, phosphorus and potasresult of effluent discharge has also been sium-are considered.

The sustainable loading rates were calculated for given climate and effluent data using the p rocedure recommended in the gu ideli nes (Beavers, 1996) and entered into a program, ComputerAided Design of Effluent Irrigation (CAD-Effiuent) (Hu and Pigram, 1998; Hu et al., 1998). Twenty-nine locations were selected to cover different parts of Queensland, plus two from other states. The climate data fo r the considered locations were the long-term mon thly records (50 to 100 years, depending on the data available). T hree sets of eilluent quality data were used for comparison. T he data ca me from Mt St J ohn Sewage Treatment Plant in Townsville and Caloundra on the Sunshine Coast (both in Queensland) and Feigin et al. (1991) . The nutrient concen trations in th e effiuen t are prese nted in Table 1. The nitrogen co nc en tration o f Townsville effluent (30.3 mg/L) is very close to that of th e Sunshi ne Coast (31.3 mg/L) and within the range of the lite ratu re values (Feigin et al. , 1991). The phosphorus concen tration changes from Townsville (21.5 mg/L) to the Sunshine Coast (6 rng/L) The phosphorus concentration ofTownsville is even higher than the maximum value in the literature. Therefore, three phosphoru s concentrations were selected: 6 mg/L (low), 10 mg/L (medium), and 21.5 mg/L (high). There is no potassium concentration available for the Sunshine Coast. However, Feigin et al. (1991) indicated that potassium added to efiluent through domestic use is 7- 15 mg/L.

Table 1 Nutrient concentrations of different effluents (mg/L)

Table 2 Assumed effluent concentrations (mg,'L)

Effluent sources

Nitrogen Phosphorus Potassium

Mt St John Sewage Treatment Plant 30.3 Sunshine Coast 31.3 Literature ran ge 10- 50

21.5 6 6- 17

14 Not available 10-40

Material and Methods

Reference

Effluent

pers. comm. Cosser, 1997 Feigin et al., 1991, p.24

Set 1 Set 2 Set 3

Nitrogen

Phosphorus

Potassium

31 31 31

6 10 21.5

14 14 14

WATER MAY/JUN E 1999

39


WASTEWATER Table 3 Water assimilation capacities, nitrogen and potassium assimilation limits and phosphorus adsorption capacities (g P/kg) required for soil to retain excess P for 50 years Location

Coolangatta Southport Caloundra Cleveland Caboolture Brisbane Maryborough Beaudesert Gympie Ipswich Bunda berg Toowoomba Katanning Bendigo (Vic) Warwick Wandering Yeppoon Mackay Gunnedah Dalby Dubbo (NSW) Rockhampton Port Douglas Goondiwindi St Lawrence Atherton Townsville Roma Charters Towers Charleville Longreach

Water assimilation capacity (mm/a) 539 554 555 629 669 729 NC1l 790 796 799 876 885 944 1006 1015 1062 1126 1135 1175 1199 K12l 1203 1260 1290 1320 1326 1357 1450 1571 1597 1807 1929 2189

For effluent concentration: 6 mg P/L

10 mg P/L

P .,dsorption

0.19 0.20 0.20 0.26 0.29 pl3 ) 0.33 0.37 0.38 0.38 0.43 0.44 0.48 0.53 0.53 0.57 0.61 0.62 0.65 0.66 0.67 0.71 0.73 0.75 0.75 0.78 0.84 0.93 0.95 1.10 1.18 1.37

0.63 pl3) 0.66 0.66 0.77 0.83 0.93 1.02 1.03 1.03 1 .15 1 .17 1 .26 1.35 1 .37 1.44 1.54 1.55 1.61 1.65 1.65 1.74 1.79 1.83 1.84 1.89 2.03 2.22 2.26 2.58 2.77 3.17

(11 theoretical nitrogen limitation for an effluent concentration of 31 mg/L N (2 )

potassium limitation for an effluent concentration of 14 mg/L K (31 phosphorus limitations for soil adsorption capacity of 0.3 g/Kg

Considering Queensland's industry and domestic combination, it is reasonable to use the value of 14 mg/L (as from Townsville). Therefore, three sets of nutrient concentrations were used for this investigation (see Table 2) . Bluegrass is a common urban lawn in Queensland and was selected as the irrigated plant for this investigation. Its nutrient removal capacities are: N = 224 kg/ha/a, P = 27 kg/ha/a, K = 167 kg/ha/a (Beavers, 1996).

Results and Discussion Asslmllatlon Capacities of Water and Nutrients Based on rainfall and evaporation data, and applying the concept of water balance, the assimila tion capacity for water itself ranges from 539 mm/a in subtropical Coolangatta to 2,189 mm/a in arid Longreach (see Table 3). Based on the assu med nitrogen con centration of 31 mg/L and the removal capacity of bluegrass, up to 224/31 x 100 =723 mm/a of irrigation could be safely applied , i.e. for the first six cities on the list, water assimilation is the limiting factor. Beyond that, nitrogen assimilation starts to become limiting, though the nitrogen balance in irrigation is more complicated than just 40

WATER MAY/ JUNE 1999

= P ,oil = pinput -

plant uptake

(1)

21.5 mg P / L

required soil adsorption capacity, g P/kg soil 0.04 0.04 0.05 0.08 0.09 0.12 0.15 0.15 0.15 0.18 0.19 0.21 0.24 0.24 0.26 0.29 0.29 pl3 ) 0.3 1 0.32 0.32 0.35 0.36 0.37 0.38 0.39 0.43 0.48 0.49 0.58 0.63 0.75

required soil adsorption capacity can be estimated as

plant uptake, so this region can be extended. For potassium, the safe limit is 1,193 mm/a- i.e. down the list to Gunnedah, a total of 19 cities. However, fo r p hosphorus, the lowest concentration, 6 mg/L, allows only 450 mm/a of irrigation; the medium concentration, 10 mg/L, allows 270 mm/a; and the high concentration (e.g Townsville, 21.5 mg/L) allows only 126 mm/a. Thus phosphorus is the most critical element for determining the sustainable loading rate. Even at the low concentration (6 mg/L) the capacity for phosphorus assimilation (450 1111n/a) is fa r less than the capacity for water and other nutrient assimilation. Potential to Relieve Phosphorus Limitation In the Queensland guidelines (Beavers, 1996), the phosphorus loading rate is recommended to equal the crop removal capacity. However, in other references (Overcash and Pal, 1979; R yden and Pratt; 1980; Broadbent and Reisenauer, 1988), phosphorus loading rate is estimated as the sum of plant removal capacity and soil adsorption. Therefore, if the soil adsorption is considered, there may be potential for relieving phosphorus limitation. If the plant removal capacity is given, the

w here Padsorption = phosphorus adsorption capacity required in kg/ ha/a P,0 ; 1 = phosphorus remaining in the soil after plant removal in kg/ha/a Pinput = phosphorus applied to the land by effiuent irrigation in kg/ha/a Plant uptake = phosphorus taken up by the plant in kg/ha/a

The phosphorus adsorptio n capacity can also be expressed as

Psorpt1on . xN = Psorptio11 xN x = soil mass 10 x D x e

(2)

where x = required adsorption capacity in g P/kg soil N = the life period of the effiuent irrigation system (year) D = soil depth (or root zone depth) in metres e = soil bulk density in kg/m3 If the plant is irrigated based on the water assimilation capacity, the amount of phosphorus removed by the bluegrass plant is 27 kg/ ha/a (Beavers, 1996) with a root zone depth of 50 cm. Assuming a project life of 50 years, the required soil adsorption cap acities to relieve the phosphorus limitati on for different locations were calculated and listed in columns 3,4 and 5 of Table 3. Laboratory analyses indicated that the adsorption capacity of Queensland soils varies from 0 .05 g P/kg soil (low) to 1.8 g P/ kg soil (very high) with median capacity of about 0.3 g P/kg soil (R eedman, 1996). Assuming a value of 0.30 g P/ kg soil, if the phosphorus concentration of effiuent is 6 mg/L, 14 locations can be irrigated _a t water assimilation capacity. If the phosphorus concentration of effiuent is 10 mg/L, only five locations are feasible. At 21.5 mg/L, no location seems suitable, since the high value of 1. 8 g P/kg soil occurs only in a very few isolated locations.

Conclusion The assimilation capacities for water and nutrients at 29 locations in Queensland and two in other states have been estimated using CADEffiuent model. The analysis of the results indicates that phosphorus is the limiting factor for all the cities if the Queensland guidelines are used for the design calculation. Further analysis shows that even if soil adsorption is considered as a phosphorus removal pathway, if the phosphorus concentration of eilluent is greater than 10 mg P /L


WASTEWATER (the median phosphorus con centration) ove rload will occur in m ost loca tio ns. T h erefore, a detailed investigation of soil phosphorus adsorption capacity should be undertaken before an effluent irrigation system is installed in Q ueensland. Nitroge n is th e second limiting fac t or for effl u en t loadin g rate. A fu rther study on nitrogen transfo rmation processes is requi red to unde rstand the pathways of the nitrogen input through effl uent irrigation and to dev elop the procedure to relieve its lirni tation to the sustainable loading rate. O verall , water assimilation shou ld no t be considered as the only factor for effl uent irrigatio n design in Q u eensland. C areful consideration and moni toring of n utrients is required during efflu ent irrigation. Alternatively, some method of nu trient reduction in the effluent may have to be considered . It is noted that phosphorus conce ntrated in the resulting sludge m ay be transported to more distant areas.

References B eavers P D (199 6) In terim Gllidclines

for R ellsc or Disposal of R eclaimed W astewa ter. Queensland De partm ent of Natural R esou rces, Australia. Broadbent F E and R eisenauer 1-1 M ("1988) Fate of W astewater Con stituents in Soil and Grou ndwater: N itrogen and Phosp horus. In Irriga tion with R eclaim ed

M llnicipal Wastewa ter - a Gllidancc Manllal, edited by G Stuart Pettygrove and Takashi Asano , Lewis Publishers, Inc., U SA, pp. 12- 1 to "1 2-"l 6. C o sser P R (1997) ed. Nlltricncs in Marine

and Esw arine Environments, State of the Environment T echnical Paper Series (Es waries and the Sea), Department of the Environm ental, Canberra. Feigin A, Ravina I and Shalhevet J (1991) Irrigation with Treated Sewage Eilluent. Springer-Verlag, Berlin. H u X and Pigram J (1998) Computer-aided D esign o f E ffiu en t Irriga tion, l. Calculation Procedure. (U npublished ) Hu X, Shi L and P igram J (l 998) Compu teraided Design o f Effiuent Irrigatio n , ll . C o m pu ter Program. (Unpublished) O vercash M R and Pal D (1979) Design of

Land Treatment Systems for lndllstrial Wa stes-Th eory and Practice, Ann Arbor Science P ublishers Inc. USA . R eedman T (199 8) Effiu ent Irrigatio n Design: D etermination of Initial Phosph oru s C oncentration for Adso rption Measurement. Hono urs thesis at James C ook U niversity. R yd en J G and Pratt P F (1980) P hosphorus R emoval fro m W astewater Applied to Land. Hilgardia, 48: 1-36. Sm ith S V, Kimmerer W J , Laws EA, Brock R. E and W alsh T W (1981) Kaneohc Bay

Sewage Diversion Experimen t: Perspectives on Ecosys tem R esponse to Nutritional Pcrwrbation. Pacific Science, 35: 279-395.

Acknowledgements T he author tha nks Tanya R eedman, Ben M illar and Amanda R eed for providing the calculation res ults of the ir design proj ects.

Author Dr Xiandeng Hu is a lec turer at the School of Enginee ring, James C ook University, T ownsville Q ld 4811.

BOOKS Assessment of Stormflows in Sewerage Systems A S Flinders and M Poon, March 1998, Urban Water Research Association of Australia Report No. 133, ISBN 1-876088-39- 7, $60 from A WWA Bookshop Most water utilities are interested in un de rstandi ng and quan tifying the magnitude o f the inflow and infiltration problems associated with their catchm e nts. T he opera ting data available provide indications normally bu t usually have not been obtained through a structured monitori ng regime. Small sewerage co mmuni ties u sually have lirn..ited resources for addressing issues. T h ey can provide only basic data on problems such as complaints from the public. They also lack record s of wee we th er events and overflows followi ng dty weather. T his mea ns that the need for mo re informa tion and better data on inflows and infiltration to collection systems is becoming mo re important. It w ill

eventua lly have to be integra ted with se werage m ain tenance managem ent and managem ent o f ove rfl ows. For example, serious situations of overflow or failure are associated with persistent co mplaints and penalties fo r causing pollution. Major cases will obviously require the use of fl.ow modelling to understand and predict the inflow and infiltration problem in detail in order co design corrective measures to preve nt pollu tion incidents in the fu tu re. In these circumstances, the use of flow mod elling, whe ther time se rie s o r event-based modelli ng, is appropriate. T he wo rk reported in this study indicates that there arc a lot of relevant data available fro m the operation o f sewerage infrastructures-it just needs to be analysed in a better manner. T he me thods presented h ere allow a preliminary analysis of data. T he m ethodology ca n be fu rther developed to allow alternative strategies for sewer design. Dr Diane Wiesn er A WWA Bookshop WATER MAY/J UNE 1999

41


BOOKS Treatment Innovation for the Next Century-INNOVATION 2000, £30 A compact disk is now available of the proceedings of the INNOVATION 2000 conference held by the European Water Pollution Control Associati on (EWPCA), the Water Environment Federation (WEF) and Anglian Water from 7-10 July 1998 . T he CD contains 43 open forum papers covering biological treatment, solids removal, membrane technology, disinfection, odour control and biosolids management. Authorship is from various UK and US water companies, universi ties and institutes in the UK, Europe, J apan and USA, and consultants and manufacturers. Although the subject matter is as diffu se as may be expected from a conference d ealing with wastewater treatment fo r the next century, there were no real surprises. Perhaps because the proceedings of the conference were not published in book form but in CD form, most of the papers were longer than normal, allowing more detail to be given of the manufacturers ' names and details of eguipment. The papers on membrane technol-

Now for the negatives. While the manual draws on the expertise of many authors who are local government officers, consultants, academics and researchers, we are given their names, b u t no credentials. Is the target audience their colleagues and peers? H ave the c hapters been subject to external review? H ow can the inexperi enced reader-in pa rticular, the graduate who needs a 'road-map' to pilot their way through a projectThe Constructed Wetlands judge the guality of the information Manual provided and the advice tendered Department of Land and Water Conservation (DL WC), 2 volumes, without some details or acknowledge443 pp., Sydney, 1998. ISBN 0 7313 ment of the authors' qualifications and 1329 6. Available only from DLWC, professional affiliations? The publication is also limited by its tel. (02) 9228 6415 for $185 plus postage on New South Wales, especially focus There is not much that this comprein discussing legislation, p ublic health hensive manual doesn't cover in the field of wetlands management. It is and local government procedures. The treatment of more universal well presented, clearly laid out, and topics related to resources and wetlands well illustrated and referenced. T he 26 chapters are packed with results in a not unexpected level of important fac ts about algae, macro- generalisation, w hile some locally phytes, vegetation, soil, water quality, pertinent issues do not gain place in pollu tion control and climate issues. print, e.g. the problems associated with Other topics are public health, legisla- limiting the impact of rural and tio n, design criteria and practical agricultural industries on local catchconsiderations su ch as budget, soil ments. Dr Diane Wiesn er parameter variables and availability of A WWA Bookshop materials. ogy, water reuse of industrial and domestic wastewaters and disinfection methods would be of particular interest to a number of professionals in the business. The papers are stored in PDF files (Adobe Acrobat format) and can be easily read or printed out. Frank Bishop Egis Consulting Australia

AWWA BOOKSHOP

SPECIALISING IN ENVIRONMENTAL SERVICES TO THE WATER INDUSTRY ~

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These specialist publicat ions are now available through the AWWA Bookshop: • water engineering, environmental sc ience and hydrogeology titles f rom A A Balkema Publ ishers, Netherlands • CSIRO environmenta l sciences and water resources titles

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• wetlands, groundwater and stormwater tit les from CRC Lewis, North America • assorted water and wastewater titles from Oxford Un iversity Press

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42

WATER MAY/ JUNE 1999

Contact Dr Dia ne Wiesner on tel. (02) 9413 1288 email: dwiesner@awwa.asn.au 9 am to 1 pm (EST) Monday to Friday


ENVIRONMENT

In 1992, ANZECC released a 11st of water quallty guldellnes, with the codicil that they should be considered for revision after three years. Seven years later, after a conslderable amount of Input from scores of workers a new draft has emerged and a round of public consultation Is soon to commence. Why the long delay? Malnly because a completely new concept has been engendered. There Is no longer a focus on 'magic numbers,' but, rather, a philosophy of risk assessment on a site-specific basis.

The article by H art, Ma her and Lawrence in the May/June 1998 issue of W at er fores hadowed this approach. At a workshop in Geelong, Victo ria in February 1999-the first of a number of similar seminars-a large audience of both environmental scien tists, analysts and industry personnel discussed the impact the new pri nciples were likely to have. C h ris Humphrey of ERISS, th e Environmental R esea rch Institu te of the Supervising Scientist, based at J abiru , No rthe rn Te rritory (which carries out research to moni tor and assess the effect of mining in that sensitive ecological zone) recently took over from Kevin M cAlpine in charge of the developme n t o f the docume nt. H e stressed that there is a major difference between 1992 and the present. Initially, the only government body involved was ANZECC , but beca use of the need to

balance ecological and econo mic va lues in a sustainable manner, ARMCANZ is now involved, which will imply a more lengthy governm ent review period. This will be followed by public review in abou t O c tober 1999 and then hopefully endorsement in 2000, when it will be backed by the Fede ral Government. The strategy is to aim at sustainable ecology while maintaining economic and social developmen t. The draft guidelines are in fi ve volumes, plus a summa1y which itself is about 90 pages long. Volume 1 provides the actual guidelines for each environmental value. The o the r volumes discuss the rationale behind selection of the indi cators and the various trigger values . The next spea ker at the seminar was Barry Hart from the Water Studies Centre, C R C for Freshwater Ecology, M onash University. H e outlined the new concepts and highlighted some of the deficiencies of the 1992 guidelines including: • only two ecosys tem types were con sidered, freshwater and marine • mainly single threshold values were quoted and ranges were provided for nutrients • the site- specific concept was introduced but not developed • the concept of biological/ecological indicators was only briefly introduced , with little guidance as to how they could be used. The new fea tures are: • six eco system types are dealt with, including New Zealand examples

• issu es are considered, not just individual indicators • risk-based assessments are the key • site-specific assessments, which may lead to the need for more information • use of biological assessme n ts to accompany physico- chemical mo ni toring and assessments. The most important concept is that 'trigger values' are being sp eci fied, ra ther than presc ri ptive numbers. A trigger value (T V) is a prom pt to investigate fu rther, rather than a dead stop. This is discussed in the paragraph below on risk assessme nt. T hroughou t the gu idelines, tri gger valu e ranges are suggested , with here and the re default values if insufficient data are available. The guidelines cover: • aquatic ecosystem protection • aquaculture and human consumers of aquatic foods • agricultural water use • rec reational wate r qu ality and aesthetics • drinking water quali ty (as in NHMRC 1996). Indu strial water quality is not covered, and the workshop considered only the guidelines for ecosystem protection. In the new guidelines for the protection of aquatic ecosystems, six ecosystem types are considered. These are upland rivers, lowland rivers, lakes and reservoirs , wetlands, estuaries, and marine wate rs. Three levels of protection are considered: high conservation va lue/ p ristine; slightly-m oderately distu rbed; and highly disturbed . WATER MAY/ JUNE 1999

43


ENVIRONMENT Issues T he major issues w hich can affect m os t syste ms are the impacts o f n uisance algal grow ths and the effects of di ssolve d oxygen, suspended solids, optical properties, salinity, tempe rature, pH and toxicants on t he resi de nt populations. These must be considered in a holistic m anner, rath er than focusing on a single effect. In the revised guidelines, a n ew issu e is introduced, the n eed for enviro nmental flows.

there still seems to be a high risk, th e flow rate of the river (o r retention time) should be considered. Ifat the end the re still seem s to be a risk, i t may be decided to un dertake a fu rthe r study befo re insisting on lower nutrient limits.

Physico-chemical Parameters

Bill Mahe r of t he Unive rsity o f Canberra concentrated on the physicochemical parame ters. The 1992 guidelines specified 'magic numbers' but i t was found in practice that they did not w ork at achieving their real ends. T his created conflict b etween wo rkers and Risk-based Assessments The guidelines attempt to account regulators. T he need to identify the for the variability and complex ity of the 'i ssues' foc uses managemen t on the natural world, so ranges are often outcomes, not the numbers themselves . quoted , rather than single numbers. While the decision-tree approach will Since ri sk is defin ed as hazard times entail more work and more professional exposure, then the co ncept of site- j udgemen t, it w ill result in less conflict specific bioavailability of th e substance and potential savings to industry. All this has to be based on commuin that environment m ust be considered nity values, and expectation s, for each when assessing the TV fo r a particular case. It is pointless to insist on pristine toxicant or nutrient. conditions w hen the com munity, with H ierarchical decision frameworks are resp ect to a somewhat m odified stream , used so that meaningful guidelines ca n is happy w ith conditions which have be develop ed. These inco rporate siteexisted for some years. T he object is to sp ecific environmen tal information and maintain and i f possible gradua lly take account of the natural variabili ty of enha nce t he quality of a partic ular aquatic environmen ts. For example , aquatic environment, n ot to manage the light availability is a key factor control- stressors for their own sake. ling th e growth and survival of b enthic T he concept o f 'modifiers' was plants. In naturally turbid waters, the discussed, e.g . the role of pH and redox depth at which light becom es a limiting poten tial in either locking up or releasfactor is shallower than in less turbid ing m etals, or the role of turbidity on waters. T he selection of a water clari ty algal growth. These are vital to the guid eline would therefo re take into con cept of th e ri sk assessment approach. accou nt these site- specific co nsidera- An example was the investigation to tions. de tennine the bioavailability of copper T he d ecision fra meworks recom- in the Lowe r M olonglo effl uen t. mend incorporation of th e additio nal Although the coppe r w as higher than information whe n guid eline trigge r the 1992 'limit,' it was so complexed by levels are exceeded and there is a risk of the organ ics present that it was unavailan impact o ccurring. able to ca use significan t bi ological It is not mandatory for hierarchical effects. In conseque nce , the coppe r decision frameworks to be used in the discharges from the Lower Molonglo development of a guideline. W hether Sewage W a rks were deem ed not likely they are used dep ends on the resources to cause a problem. available and the relevance o f the steps As well as trigger values, the concept to a specific situation. of load over tim e has been introduced. This was illustrated with th e assessment Site-specificity of a safe annual load of sediment to In each particular case, the values to be released from ACT into the be protected must be defi ned. After Murrumbidgee River. It had been m eas ure ments, a decision tree is observed that the benthic community employed. If the measured values fall could only tolerate deposition of less below the recom mended TV, there is than 2 111111 per year of sediment in critin o risk. If they lie within or above this cal reaches 100 km downstream from range, the n ext stage is to consider other the border, the criterion being a ratio of fac to rs w hich might affect the real issue. obse rved nu mber of macroinvertebrate Fo r example, in considering the species to the expected or p redicted effec t of nu trient concentrations on num ber of m acroinvertebrate species algal growth, the availability of light is being greater than 0.75 for four years also a factor. If the stream is highly ou t of five. T his translated to a discharge in the turbid, n utrients are not likely to be critical. T his could shift the syste m into range of 60,000 to 160,000 tonnes p er one oflow or medium risk. H owever, if year, dep ending on river flows. 44

WATER MAY/JUN E 1 999

Toxicants J ohn Chapman fro m th e N ew South W ales Enviro nment Protection Autho rity Centre fo r Ecotoxicology gave an overview of how the TVs were derived fo r toxicants. Th e team searched the literature for more than 20 chemicals, covering the USEPA 'AQUIRE' ecotoxicology database as we ll as Dutch , English, Canadian, Danish and WHO sources along wi th Australian ecotoxicology results. They ranked the results into fo ur grades, of decreasing confiden ce: • m ultiple species chroni c toxicity (1nicro, mesa , field) of wh ich there was little available • single sp ecies chro nic toxicity in the lab (th e difficulty was defini ng a consistent end-point) • single sp ecies ac ute toxicity (no w orries about the end-point there) • QSAR (equations that relate structure and physico- chemical properties, e.g K ow, to toxicity) This huge mass o f data was scored in terms of reliability, e.g. data on metals toxicity were accepted only w he re the mod ifiers Ca/ M g and pH had been consistently monitored. The effects co nsidered were mortality, im mobility, reproductive ability, population growth, individual growth and photosynthesis. In the 1992 guidelines the limits were set by dividing the lowest toxicity figu re from a range o f such effects levels by an arbitrary factor. The n ew trigger values are m ostly derived using a D utch log/log probability approach at the site- specific application stage . In the aquatic environment, a 1ninimum of five sp ecies from four taxonomic groups must be assessed, and the TV derived from the log- logistic dis tribution of to xicity da ta for all species. If there is evide nce of bioaccumulation, a further safety factor may be applied that uses all of the toxicity data. In the absence of adequate toxicity data, 'inte rim guidelin es' have been assessed, and, at worst, an 'environmental concern level' suggested , p ending fu rther data . J ohn C hapman gave the framework for applying the TVs to specific sites. T o assess a site, commence with analysing the total ' unfiltered' concentration of possible toxicants, then determine: pH , hardness, dissolved organic matter, etc. or the 'modifie rs.' The type of ecosyste m and the level of p rotection desired (e.g. pristine o r urban) and the type of chemical must be considered (even th e commercial fo rmulation of a h erbicide can modify an effect). Background concentrations are considered at this stage. O n the other hand, if there is a mixture of


ENVIRONMENT toxicants, additivity o f toxic effects, syn ergy (or antagonism) m ust also be considered. The scheme for applying the guidelines leads ultimately to the opti on of direct toxicity assessment of complex mixtures.

Speciation

a habitat, re fuge and food so urce. H owever, remediation is too late for most urban areas and the guidelines ca n only aim to identify and protect uncontaminated areas. In suggesting TVs, the partition of a substance between the solid phase and the pore water must be considered, being affected by the organic content, grain size, oxic conditions, and particularly the sulfide content. The role of iron Oll.')'- hydroxides as an adsorbent has also been identified. Consequently, a set of interim sediment guidelines has been proposed, and further work w ill proceed to app ly these to manageme nt situations. The guidelin e valu es are based on those developed by Long and co- workers in North America from a large sediment toxicity effects database. A low and high value are quoted corresponding to the effec ts range low (lowe r 10% of conce n trations producing adverse effec ts) and effec ts range m edian (median of concentration s produ cing adverse effec ts) . Agai n , a decision tree is provid ed to allow consideration o f mod ifying effec ts that would reduce the potential bioava ilability of sedime n t co ntaminants.

T he consideration of metal speciation as a control on metal bioavailability was taken up by Scott M arkich o f ANSTO. This aspect feeds into the site- specific assessment of metals. T he toxi city of a meta l is determined by its abili ty to transfe r across the cell me mbrane, w hich may be easy fo r a free ion , but much more difficult if it is in the form of a complex. As an exam ple, the toxicity of coppe r to Chlorella in the laboratory has bee n measured as 3 ug/ L , but in Fly River water concentration s up to 14 µg/L had no effect. In other words, the copper was in a fo rm w hic h was not bioavailable. To allow fo r such factors, a hi erarchy of t esting is recommended. Analysing th e total unfiltered conce ntration is the start, bu t if it is above the guideli ne TV it i s necessa ry to take into account hardness, alkalini ty and pH. H ardness is very important, and algorithms have been derived for its modifying effects. If Biological Assessment the di ssolved conce ntrati on exceed As mentioned in the in troduction, the hardness- co rrec ted gu ideline TV, th e new guidelines include far more so m.e measure of speciati on may be conte nt on biological assessment, on the employed. T his ma y involve eith er prem ise that o nly bio logy can summate m easuring or modelling the bioavailable the effects o f all co ntami nants in a metal concen tration. particula r system . C h ris Hu mphrey Once agai n , u sing copper in a hypo- (ERISS) d isc ussed th e chap te rs in the tical exampl e, the total extracted by Volum es 1 and 2, which cover selection acid may be 14.5 µg/L, w hich on fil tra- of suitable ind icator o rga nisms, co mpotion is reduced to 6 µ g/L, and when sition , diversity, function and com parispeciation is co nsidered, only 2 µ g/L son and assessment of th e measu red may be active. H owever, it was stressed responses against data from appropriate tha t if the guideli ne TV is still exceeded reference systems. it wou ld be essential to perform a direct T he guidelines cater for three types toxi city assessment on a sensitive target o f assessment . On a broad scale, speci es. This is far more expensive than AUSRIVAS enables a rapid fi rst pass chemical analysis. assessme nt to be performed . The next Discussion on all these p oin ts was level is tb e early warning necessary fo r useful. M embers of the audience drew high conservation sites, or major develattention to di fficulties wi th pulse and opmen ts w hich might affect the aquatic multiple discharges, long-term effects, environment, where sub-lethal or othe r limits of analytical techniques and th e responses are used for rapid detection or effect of a shift of tox icant from one to loca te potential hotspots. The third c01npartment to another downstream. level is an assessment of the biodiversity For example , transfer of a toxicant from or ecosystem response , trying to answer a turbid river to a wetland w ith lower questions such as 'how can we assess the DO, pH and turbid ity co uld we ll ecological importance of this impact or increase bioavailabili ty. pote ntial impact?' M anagement protocols are suggested Sediments in the guidelines , to assist whe re For the first time, the gu idelines decisions have to be made in real time include a sec tio n on sedime nt quality. between the conservationist and the G raem e Batley of CSIRO Centre d evelope r, an d furt h er res earc h is fo r Adva n ced Analytical C h emist ry proceeding on this aspec t. di sc u ssed the approach adopted. Sedimen ts in aquatic e nvironme nts Monitoring con sti tute both a sink and a source for W hat new developments have been nutrients and chemicals, as well as being applied to physico- chemical monitor-

ing programs? What is the expected m onitoring effo rt for all indicators at a si t e? H ow can t he biological and physico- chemical assessments be integrated? A chapter explores these and other issues. C hris le Gras of ERlSS highlighted some of the content of the chapter on monitoring and assessment. H e outlined the m onitoring effort recom me nd ed to apply for different levels of p rotec tion and for existing or planned developments. The advantages of integrated monitoring programs are an increase in inferential power and a possible reduction in sa mpling costs, but th ese will be di fferent for d ifferent situations. Ce rtainly, if biological effects data gives a clear NOE result, this could save industry costs, so the need fo r co mplementary biological assessment is obvious. Beyond that, a co mb ined physicoch emical and biological sampling program can be devised. It was noted that physico-chemical samples are easier to take and preserve than biological sa mp les and also th at biological monitori ng is more often very spa tial, w hereas physico- chemical monitori ng is ofte n more temporal over a smaller number of sites. N oneth eless, a wellplanned ca m paign can reduce th e number of fi eld excursions. This secti on of th e gu idelines is in effec t a stand -alone text book o n m ethods and includes recommended statistical methods to compress a wide database in to a 'single number. '

Conclusions? In concluding th e workshop , Barry H art said th e draft guidelines, in adopting a ri sk-based approach , wi ll put Austral ia ahead of the rest of the world. This is a p ragmatic attempt to involve all the stakeholders in ach ieving the required qual ity of the environment and during the pu blic consul tation process the views of industry, agriculture and o the rs wi ll be incorporated . There is an expectation that the guidelines wi ll be released for public com m ent in about July 1999 and given the interest both natio nally and internationally it is im portant that the bureaucratic processes do not further delay th is process.

Reporter E A (Bob) Swinton is the Fea tures Editor of Water. Prior to his re tiremen t from CSIRO in 1987 he was a research scienti st specialising in desalination, water and wastewater treatment. H e was Chairman o f the Water Editorial Board fo r som e years and is a past p resident of th e A WWA Vi ctorian Branch . ln 1994 h e was awarded H onorary Life M embership of the Associatio n. WATER MAY/ JUNE 1999

45


BUSINESS

Government water and sewerage services will be free of the goods and services tax (GST) proposed by the Australian Federal Government, so why does the water industry have to think about it? At a recent meeting in Melbourne of AWWA and the Victorian Institute of Water Administration, David Kuhne, a senior manager with Chartered Accountant KPMG, presented an answer to this question. Water Features Editor EA (Bob) Swinton was there to report. The draft KPMG report commissioned by the Water Services Association of Australia (WSAA) has been circulated to a number of similar organisations across Australia. The simple answer to the question of Treasury for policy decisions and the 'service' and is likely to be taxable. R epairs may be classified as a plumbhow a GST would affect our industry is Australian Tax Office for interpretathat every water business will have to tions. A group has visited New Zealand ing service rather than a sewerage address the GST properly-otherwise, to gather experiences from the water service. It is notable that in the UK business there. The fundamental issues where reconnection after non- payment they will lose a lot of money. Whether the business is a GBE, a to be resolved are clarity, resources, of a bill is free of VAT a new connection is liable. corporation, an arm of local govern- education and transition. O ther incidental taxable ' services' ment, or a company in the chain of could include water meter fees, applicawater and sewerage supply and treat- Clarity me n t, the proposed GST will have T reasu1y has not yet clarified a tion fees, tapping/tee insertions, and, impact. It is the greatest and most nu mber o f ambiguities. It has been even mo re complicated, any 'up-front' extensive tax reform ever to be tackled stated that water and sewerage will be develope r contribu tions. Sewerage services are GST-free, but in our lifetime. GST-free, but not necessarily for all It is assumed that the GST will supplies such as wastewater, drainage, the current thinking at the Australian eventually pass through the Senate, commercial and agricultural supplies, Tax Office is based on UK experience, perhaps with some amendments, but w here they constitute a significant input where combined sewerage and drainage is the norm. none likely to impinge on the water to the businesses. So will separate drainage become a business. It is almost certain that it will If a fixed p rice water supply to a begin to apply to all businesses in customer or a trade waste agreement has taxable service? As with water supply, contracts wri tten from July 1999 and been negotia ted for, say, 10 years, tax might apply to i ncidentals such as repair and replacement of sewers, longer term supplies commencco nnection fees, sale of plan s, ing before the GS T but which ' ... every water business will have to laborato ry fees and regula to ry straddle 1 Ju ly 2000. This is so even though the date of 'Royal address the GST properly-other- charges. Most sign ificant of all, trade waste charges may not be assent' may be later and the actual wise they will lose a lot of money.' defined as a sewerage service in application will commence in the vario u s Australi an water July 2000. The supply o f water itself and the bracketing the J uly 2000 date, then after supply acts, and consequently GST collection and treatment of sewage w ill 1 J uly 2005 the water business must pay would need to be charged on taxable not attract GST, so the assumption is the Australian Tax Office one eleventh supplies after 1 J uly 2000. If a supply is taxable and it is made to that water rates ostensibly will remain of the contract price as GST. The u nchanged. Not so! Any number of purchaser can claim as a credit the GST a registered business, the GST cha rged by a water authority will be a credit to ancillary services and commercial activ- payable by the supplier. The separation of water rates as a the business. In these si tuations the ities may well be taxable. Certainly, purchases of inputs such as equipment, service c harge and a consumption water authority will still need to justify consultancy etc . will have their compo- charge may lead to the service charge any increase as the Federal Government nent ofGST added to the invoice and it attracti ng GST. This will certainly be will not expect to see a full 10% rise is up to the water business to file the resolved before rates w hich span past 1 because of GST. Consequently, WSAA and others are July 2000 are set. relevant claims for GST credi ts. The situation with a recycled water applying to T reasury and the Australian At the beginni ng of 1999 there was a raft of unresolved questions which are contract has to be clarified. T he water T ax Office to define more exactly the currently being addressed by WSAA itself may or may not be GST- free, but nexus between water or sewerage and and si milar organisations. A working the provision of the necessary in fra- the services necessary to maintain the group has been set up to approach both structure (pipes, pumps, meters etc.) is a supply or collection. 46

WATER MAY/JUNE 1999


BUSINESS Resources Once clarification has been obtained , water businesses must then design their accounting systems to ensure separation of GST-free and taxable inpu ts/outpu ts, leaving a clear audit trail which the Australian Tax Office will undoubtedly chec k. All co ntracts, existing and proposed, wjl] have to be reviewed.

Education Purchasing officers will have to deve lop a new paradigm. They cannot accept a bland 10% increase from a suppli er, because the GST system is designed to replace a whol e raft of taxes such as wholesale sales tax. Prices may even be reduced. Accounts payable systems must b e amended to include GST credits. Even staff packages will be affected by the 9.09% fringe benefit tax rise.

Transition GST will be payable on supply or importation on or after 1 July 2000, so th e d ate of actual supply or removal is vital. C redits continue to be claimable from August 2000. Supply of a ' service', e.g. a co nsultan cy , will be co nsidered to date from when it is 'd o ne,' or the relevant proportion thereof. Real estate property will date from when it is ' made available' to the recipient. For constru ction co ntracts whic h bridge the July 2000 date, GST w ould apply only to work conducted after that date an d a Commissioner can be employed to assess the relevan t valuations. There is provision for review of an agreement or contract if a supply is mad e to some extent after 1 July 2000 to take account of the impact of GST, but this must be defined beforehand, and cannot include an auto ma tic consumer price index (CPI) escalator. If th ere isn 't a clause that allows an increase in price, there will be a transfe r of wealth between the purchaser and the vendor after 1 J uly 2005.

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Conclusion Obviously, there is much stilJ to be decid ed and W SAA is to be commended for commissioning the report and addressi ng the questio ns. It seems that for the w ater businesses and their suppliers, the year 2000 has m uch more seri ous implications than the Y2K computer bug!

Author David Kuhne is a Senior Manager with KPMG , Chartered Accountants, 115 GrenfelJ Street, Adelaide , Sou th Australia 5000. H is p resentatio n was reported by EA (Bob) Swinton.

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MEETINGS For information about the events listed, contact A WWA . Email info@awwa.asn.au Telephone (02) 941 3 1288 Facsimile (02) 9413 1047 AWWA CONFERENCES

OVERSEAS

2000 9-13 April, Sydney 5th Australian W aste Co nvention 10-11 April, Sydney WaterT ECH Confe rence OZWATER & OZWASTE TRADE EXHIBITION 2000 10-12 April, Sydney AUSTRALIA 1999 2-4June,Sydney,NSW

NSW W aste Management Conference and Expo '99: Resourcing the New Mi llennium, NSW Waste Boards, WMAA Fax (02) 4628 9925 6--8 July, Brisbane, QLD WATER '99 Joint Congress-25th Hydrology & Water R esources Symposium, Institution ofEngin eers, Australia Fax (07) 3369 1512 6--8 July, Brisbane, QLD WATER '99 J oint Congress-2nd lnternational Conference on Water Resources & Environment R esearch, Institution of Engineers, Australia Fax (07) 3369 151 2 13- 15 July, Annidale, N SW On-site '99-Meeting the Challenge Fax (02) 6775 1043 5- 6 August, Perth, WA Waste and R ecycle Conven tion '99, WMAA, W estern Australian Municipal Association , Western Australian Department of Environmen tal Protection Fax (08) 9322 1598 22-26 August, Sydney, NSW The Internatio nal Congress on Local Government Engineering and Public W orks, Institute of Municipal E ngineers, The Institution of Engineers, Australia Fax (02) 9251 3552

1999 1-3 June, Copenhagen, Denmark Copenhagen Waste and Water 99 Fax +45 32 51 9 636 6--10June, T ampere , Finland 6th [AWQ Symposium on Forest Industry Wastewaters, IAWQ Fax +358 3 365 2052 8-12June , Beijing, China T he 6th International E nviron mental Protection E xhibition and Confere nce Fax +61 2 9489 1890 12- 18 June, Toronto, Canada International C ongress on Membranes and Membran e Processes Fax +27 12 331 2565 13- 18 June,Jerusalem , Israel Environmental C hallenges for the Next Millennium, fWRA , AIDA E mail drorg@T avas.co.il 15- 18 June, Barcelona, Spain 2nd International Symposium on Anaerobic Digestion of Solid Waste Fax +349197511 80 20- 24 June, Chicago, USA AWWA Annual Conference, AWWA Fax +1 303794 7310 29 August-1 September, Milwaukee , USA In ternational Symposium on Ciyptosporidium and Emerging Waterborne Pathogens, AWWA Fax +1303794 7310 18-24 September, Buenos Aires, Argentina 22nd World Water Congress, rWSA AIDE Fax +54 1 325 6029 22-24 September, Christchurch, NZ Valuing our Environmen t: Dollars and Sense, N ZWW A 41 st Annual Co nference & Expo Fax +64 9 636 1234 4-8 October, Cagliari, Italy 7 th In ternational W aste Management and Lan dfi ll Symposiu m Fax +39 049 663 960 9-13 October, New Orleans, USA WE FTEC '99-72nd An nual Conference and Exposition, WE F Fax +1 703 684 2471

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Water Journal May - June 1999  

Water Journal May - June 1999