Water Journal June 2007

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Volume 34 No 4 June 2007

Journal of the Australian Water Association

OPINION AND INDUSTRY NEWS OPINION Vision and Achievement DBarnes, President, AWA Cheers CDavis, CEO, AWA My Point of View Prof Mike Young, Research Choir, Water Economics and Management, The University of Adelaide AWA NEWS Includes: National Water Commission Stakeholder Reference Group Meeting No 2; Young Water Professionals CROSSCURRENT National Issues and Policy, States, New Reports & Papers, Programs & Awards, People in the News AWA MEMBERSHIP NEWS New Members

4 5 6 8 14

20

PROFESSIONAL DEVELOPMENT EVENTS & PROGRAMS NATIONAL EVENT CALENDAR

22 28

CONFERENCE REPORTS

30

TECHNICAL FEATURES ( ·, indicates the paper has been refereed) WATER TRADING Water Trading for Melbourne and Regional Victoria Aplea for a Victorian water grid

KGan

36

ABPittock

42

RBeatty, S O'Brien

49

PEvans, NJ Arunakumoren, AMoore

54

BBoho, TTran, MHoang

59

CLIMATE CHANGE [ii The Enhanced Greenhouse Effect: Threats to Australia's Water Resources · Part 1: Scenarios for the Future Ableak scenario for southern and eastern Australia DEMAND MANAGEMENT The Economics of Supply and Demand Options: Problems with Levelised Cost Levelised costs calculations lack assessment of avoided costs GROUNDWATER [i] The Brisbane Aquifer Project The Brisbane Aquifer Project is one of the ways Brisbane is boosting its water resources MEMBRANE TECHNOLOGY Membrane Distillation - A Low Energy Desalting Technique?

Increasing mention al membrane conferences of the interesting technique

WATER SUPPLY [I] UV Spectrometry in Drinking Water Quality Management Amultiwavelength in-line spectrophotometer con be a helpful tool for real-time monitoring.

CChow, RDexter, LSutherland-Stacey, FFitzgerald, RFobris, MDrikos, MHolmes, UKaeding lffl Strategic Water Quality Monitoring for Drinking Water Safety What, where and when to monitor S Rizok, SEHrudey [ll Runoff Enhancement In Water Supply Catchments Can Western Australia's experience be applied to Sydney's catchments?

P BHairsine, J MPerroud, TWEllis

63 67 72

WATER BUSINESS NEW PRODUCTS AND BUSINESS INFORMATION · SPECIAL FEATURES: RAINWATER TANKS; PRESSURE SEWERAGE SYSTEMS ADVERTISERS' INDEX

76 90

OUR COVER Groundwater is a resource which, except for Perth and Darwin, has traditionally been overlooked as a resource for Australia '.r capital cities. This is despite long-term successful groundwater use by many major regional and rural centres (e.g. Newcastle). However, with most ofthe big storage dams being at low ebb, exploration is being conducted to assess the extent ofgroundwater resources in and adjacent to major cities. Brisbane Waters program is one such example, as summarised on page 54. Photo courtesy ofEHA ofairlift development and testing ofa trial artesian production bore at Calamvale in the south-west ofBrisbane.

Journal of the Australian Water Association

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JUNE 2007 1

~ AWA CONTACT DETAILS ~ 'Promoting the sustainable ..~ management ofwater' POSTAL ADDRESS PO Box 388, ARTARMON NSW 1570

EMAIL info@awa.asn.au WEBSITE http://www.awa. asn.au PRESIDENT David Barnes - president@awa. asn.au

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DISCLAIMER Australian Water Association assumes no responsibility for opi nion or statements of facts expressed by contributors or advertisers.

COPYRIGHT AWA Water Journal is subject to copyright and may not be reproduced in any format without written permission of AWA. To seek permission to reproduce Water Journal material ema il your request to: jsage@owa.asn.au

2 JUNE 2007

Water

Journal of the Australian Water Association ISSN 0310-0367

Volume 34 No 4 June 2007

AWA WATER JOURNAL MISSION STATEMENT 'Toprovide a print ;ournal that interests and informs on water matters, Australian and international, covering technological, environmental, economic and social aspects, and toprovide a repository of useful refereedpapers.'

PUBLISH DATES WaterJournal is published eight times per year: February, Morch, May, June, August, September, November and December EDITORIAL BOARD Chairman: FR Bishop BN Anderson, TAnderson, CDiaper, GFinlayson, AGibson, GA Holder, BLabza, MMuntisov, CPorter, DPower, FRoddick EDITORIAL SUBMISSIONS Water Journal invites editorial submissions for: Technical Papers and topical articles, Opinion, News, New Products and Business Information.

Acceptance of editorial submissions is subject to editorial board discretion.

Email your submissions to one of the following three categories: 1. TECHNICAL PAPERS AND FEATURES Bob Swinton, Technical Editor, Water Journal: bswinton@bigpond.net.au AND journal@awa.asn.au Papers of 3000-4000 words (allowing for graphics); or topical stories of up to 2,000 words. relating to all areas of the water cycle and water business.

Submissions are tabled at monthly editorial board meetings and where appropriate are assigned to referees. Referee comments will be forwarded to the principal author for further action. See box on page 14 for more details.

2. OPINION, INDUSTRY NEWS, PROFESSIONAL DEVELOPMENT Jennifer Sage, jsage@awo.asn.au Articles of l 000 words or less 3. WATER BUSINESS Brian Rauh, National Sales & Advertising Manager, Hallmark Editions brion.rouh@holledit.com.ou Water Business updates readers on newproducts and associated business news within the water sector.

ADVERTISING Brian Rauh, National Sales & Advertising Manager, Hallmark Editions Tel: 613B5345014 (direct), 6138534 5000 (switch), brion.rault@holledit.com.au Advertisements are included as an informationservice to readers and are reviewed before publication to ensure relevance to the water environment and objectives of AWA. PURCHASING WATER JOURNAL Single issues available @$12.50 plus postage and handling; email dwiesner@owa.asn.au BACK ISSUES Water Journal back issues are available to AWA members at www.awa.asn.au PUBLISHER Hallmark Editions, PO BOX84, HAMPTON, VICTORIA 3188 Tel: 61 3 8534 5000 Fax: 61 3 9530 8911 Email: hallmark.editions@holledit.com.au

Journal of the Australian Water Association

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WATER TRADING FOR MELBOURNE AND REGIONAL VICTORIA KGan Abstract _.,

For no more than a coca! of about 11 Om km of pipeline the bulk of the water systems in Victoria can be interconnected into a grid which would enable trading, not only between che cities but between rural suppliers. Even transfer across the Dividing Range would now necessitate only a 32 km link. Rather than by edict and regulation, che optimal use of water could readily be facilitated by trading at negotiated prices.

There are precedents already, both within Victoria and in ocher Scates.

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Introduction A high degree of interconnectivity in che gas and electricity infrastructure of eastern Australian scares makes possible che operation of sophisticated energy markers with che sharing of coses and benefits. This has not been the case fo r water, primarily because ic is traditionally uneconomic to convey water over long distances. But this is rapidly changing as the value of water rises due to scarcity in che face of drought, climate change and increasing demand.

Victoria has che opportunity to create che most innovative water sector in the country through the mechanism of water trading.

Central Region Water Supply Systems The Central Region south of the Great Dividing Range includes che regions of West Gippsland, Central Highlands, Barwon, Port Phillips and Westernport and the urban centres of Greater Melbourne, Geelong and Ballarac. Within this region, water infrastructures are already highly linked, so what can be called the Southern Grid is nearly complete. The Thomson Reservoir connects the Melbourne system with chat of Southern Rural Water serving che Macaliscer irrigators in West Gippsland.

The Tarago Reservoir, which will be reconnected to the Melbourne system in 2009, also serves the towns of Drouin and Warragul under Gippsland Water. Two pipelines run co Sunbury and Melton in Western Water from the western edge of che metropolitan system. Western Water

A plea fora Victorian water grid.

36 JUNE 2007

Water

Figure 1. Schematic of Victoria's urban Southern G rid and connection to the rural water market of the North.

also shares two reservoirs - Pykes Creek and Merrimu - with Southern Rural Water chat are used for the Bacchus Marsh irrigators. Central H ighlands Water which serves Ballarac, shares Lal Lal Reservoir with Barwon Water which serves Geelong; hence, both authorities can be brought into the Southern Grid by a new 42 km pipeline between Melbourne and Geelong. Blue Rock Lake is currently shared by Gippsland Water, Southern Rural Water and the Latrobe power stations. Another new 35 km pipeline between Blue Rock Lake and Tarago Reservoir will furthe r enhance the Grid, as well as a shore section running from the Melbou rne system co Westernport Water which is itself connected to South Gippsland Water through Lance Creek Reservoir.

Benefits of Troding Across the Southern Grid Water authorities within che Central Region have greatly different augmentation sources, coses and timings depending on local circumstances. Inter-basin transfers in a cooperative manner can serve to balance out these differing opportun ities and coses to achieve optimal good for che whole.

Journal of the Australian Water Association

Otherwise, the possibility arises of one authority forced into a financial and environmentally costly option chat could have been eliminated or substantially delayed by the transfer of surplus water from an adjacent catchment. The logic and sense of inter-utility cooperation is not contentious, however, the mechanism used to achieve chis may be greatly so. In particular, statutory allocations made by the Government may be subject to controversy and disputes. A sirnacion may be envisaged whereby one city has invested considerable time, effort and money in water conservation measures only co have che saved water forcefully re-allocated to another city chat has not done much to curb its wasteful consumption. The process required for statutory allocations is also cumberso me. It requires a ce ntral authority co collect info rmation, determine the truth and consistency of such information and then make unbiased judgements There exists, however, a mechanism chat is generally accepted as being fair and reasonable and, fu rther, has the merit of req ui ring little or no govern mental intervention , char is, water trading. When willi ngness to sell meets willingness to pay,

WASTEWATER RECYCLING & REUSE INDUSTRIAL WATER TREATMENT SYSTEMS

technical features

water trading it does not matter whether the surplus water is derived from fortu nate natural circumstances or hard earned through water conservation. T he agreed price per unit of water will generally be located withi n a band with che next augmentation cost of the seller as the fl oor and the next augmentation cost of the purchaser as the ceiling, plus appropriate premiums for factors such as improved water quality and increased reliability of supply. Hence, water trading tends co move che entire region cowards a more uniform cost of augmentatio n, an elegant mechanism fo r big scale optimisation chat drives itself. Light regulation may be needed co prevent distortions although a recen t study into water trading concluded chat there is no obvious need for specific regulation o f che water sector at chis time (Dept of the Prime Minister and Cabinet, 2006).

Such a grid will also provide incentives for water savings through effi ciency gains. For instance, if the Latrobe power stations or the Thomson Macaliscer irrigarors d rive down their water use, their su rplus can be placed at one end of the grid via che Blue Rock and T homson Dam connection points. Barwon Water or Western Water could then purchase these quantities at the ocher end of the grid with allowance made for any ext ras associated wi ch transfer and treatment. The price of water, as it rises over time, will make worthwhile che more expensive efficiency opportunities un til there is no longer any realistic waste across the Region or until technology makes possible the next level of p roductiviry in the use of water.

North of the Divide A large, active and sophisticated water marker exists north of che Divide within an area char encompasses the Murray, Lower Gou lburn, Campaspe, Loddon, Broken, O vens and Mirra-Micca river basins, and which claims Eildo n, Hume and Dartmouth as the major storages. There is a high degree of interconnectedness in the water infrastructure, enabling delivery of water from one part of the system co another. The water is largely used for irrigation, with Goulburn Murray Water the bulk supplier.

The Northern Victoria W ater Exchange, which was established in 1998, was absorbed by a new stare-wide exchange called Warermove in 2001. Sale of water may also be effected privately or via brokers.

From chis region, ic is also possible co trade across the bo rder into South Australia and New South Wales.

Since permanent water trading started in 1993/94, almost I 03 GL has been traded into Sunraysia, creating an additional 38 JUNE 2007

Water

15,400 ha of high value horticultural products including nuts, grapes and vegetables (The Weekly Times, August 3, 2006). Between 1997 co 2003, the area under drip irrigation grew from 6425 ha co 19,060 ha, signifying the more efficient use of water.

Since the early 1990s, water entitlements have been separated from land ownership so char they can be traded either temporarily (usually for o ne year) or permanently. T his is composed of a h igh security water right with 96% reliabiliry and a low security sales water available only in years of excess. The Victorian Government's White Paper Oune 2004) proposes reforms char will provide even more flexibiliry through the unbundling of water entitlements into three key components: a water share, a delivery capacity share and a license co use water on a site. Unbundling will allow non-water users co own water shares with lease-back arrangements and farm ers in northern Victoria will be able co trade their sales water entitlement independently for rhe first time.

North-South Water Trading T he Victorian Government's Central Region Sustainable Water Strategy (CRSWS, October 20 06), supports interconnecting water su pply systems in the Central Region south of the Divide and expanding che water market co include large industrial users and the environment. T he CRSWS also proposes co develop a governance framework co guide trading by urban water au thorities. However, it considers chat Melbourne should explore conservation, reuse and recycling options rather than purchase water fro m northern Victorian irrigacors. H owever, chis policy does not extend co regional urban centres, with Bendigo and Ballarac seeking co secure their future water supplies by purchasing from willing irrigators in the Goulburn system via new pipelines.

For water co be transferred between No rth and South, there muse, first of all, be an infrastructu re lin kage. Historically, there have been p roposals co con nect Lake Eildon co Upper Yarra Reservoir via a tunnel across the Divide, or else co divert che waters of che Big and Black Rivers co Upper Yarra and Thomson Dams respectively by tunnels.

These expensive co nceptual ideas have now been overtaken by recen t developments whereby the water systems o n both sid es of the Divide are approaching one another due co growth. Yarra Valley Water has constructed a 22 km, 450/600 mm pipeline up the Hume Corridor co supply the town of Wallan, che northernmost extension of its new supply boundary. le requires another

Journal of the Australian Water Association

32km of pipeline from Wallan co the Goulburn River near Tallarook, at which point, a pump station will be all chat is needed co participate in the water market of the North. Moderate quan tities of water p urchased can be created and transferred fo r use along the H ume; larger quantities can be conveyed further south into Greenvale Reservoir o r eastwards co Yan Yean Reservoir, or westwards co Rosslynne Reservoir for use over wider areas of Melbourne, Sunbury or Gisborne. Energy may possibly be recovered by mini-hydros on che descending pipeline. New infrastructure can be constructed co transfer any volume desired. Preliminary modelling indicates chat on a cost per ML basis, includi ng capital and operating expenses over fifry years, north-sou th water trading is comparable co cost-effective water conservation measures, is about 75% less costly than seawater desalination and abou t 90% less costly than d ual pipe water recycling for new homes. A more recent proposal is co pump water from che Goulburn River near Yea straigh t co Sugarloaf Reservoir where there is an existing treatment plane.

Through water tradi ng, the benefit of chis imported water extends across che entire Southern Grid. l e would also unite into a single water market, the T homso n, Macaliscer and Werribee irrigation areas south of rhe Div ide with che irrigation districts north of the Divide and across che border into southern NSW and South Australia.

T he concep t of a state grid to achieve such trading is illustrated in Figure 1.

The Efficiency of Water Use With a 22% reduction in per capita water use compared co the nineties' average, Melbournians are now fairl y water efficient.

In addition, metropolitan water supply systems are already approach ing the technical minimum in regard co system losses, at which point, che leakage is considered unavoidable given the p hysical characteristics of the system. In contrast, typical irrigation efficiencies in open chan nel areas are about 70% (H arding and Viney); there is a large scope for water saving in irrigation areas th rough outfall, seepage, evaporation and leakage reduction and improvements in measurement accuracy. Further savings are available at che farm level where imp roved systems and techniques can save up co 50 % in applied water. There could be corresponding benefits co the environment if the wasted water is prevented from contributing co salinisacion, water logging and nutrient d ischarge.

technical features

water trading However, che cost of imp rovement works often exceeds the marker value of che saved water. T he pip ing of open channels generally coses between $2000 - $10,000 per ML/yr of water saved while expenditure in the order of $3,00 0 per ML/yr would be required co co nvert flood irrigation co sprays. In contrast, permanent trades in northern water have averaged less than $1200 per ML/yr over the last few years .

However, rising p rices in a water marker wi ll drive investments into imp roving rhe efficiency of rural water use. Such investments may come from urban water autho rities keen co purchase the resulting water savings, a concept that is supported by 54% of respondents co a Weekly Times survey {The Weekly Times, November 22, 2006). O n the other han d, well endowed fu nds and generous incentives co source water primarily for environmental purposes may nor be cost-effective (P roductivity Com m ission, 20 06) if there are no marker sign als co check against over-investments for low returns.

The Barriers The ch ief barriers co realising rural-urban trading appear co be social and poli tical.

The com mo n perception is one of d isaster fo r rural communities if their water is diverted co q uench the thirst of urban centres, especially char of a metropolis ch e size of Melbourne. In face, with 77% of the state's water used for irrigation (over 5,000 GL/yr), a few percen t of chis will make a great d iffe rence to urban centres without appreciably im pacting on rural water use; as noted earl ier, far larger efficiency gains are possible with agricultural irrigation . For instance, a si ngle cotton farm uses on average 2,922 ML/yr (ABS, 200 6) enough for the annual use over I 4,000 households in M elbourne.

Two recent modelling exercises addressed the issue of rural economic impacts. The first of these, commissio ned by rhe Water Services Association of Australia, showed rhac regional water trading can substantially reduce water prices in Melbourne and rural Victoria, as well as increase the Gross Regional Produce for the latter, although chis is at rhe expense of regional NSW (ACIL Tasm an, 2005). The second study, u ndertaken by the CSIRO (2006), reached sim ilar conclusions and, interestingly, showed water movi ng away fro m rice and cotton farmi ng co dairying, other crops, homes and indu stries. This is a desirable o utco me, since a scarce resource should be reserved for h igher value uses.

As noted in the Australian Financial Review (Oct 2006): "Allowing fa rmers to sell what will be a small p roportion of their water rights co cities in a competi tive market will actually em power rhe farm ers rather than present chem as victims." Th is, however, may nor allay the fears of ru ral commu nities. As a result, some d istricts in the Goulburn M urray irrigatio n area have sec u p a "water bank" aimed at keep ing water rights in local areas (The Age, 2 1 Nov 2006). The bank would buy rhe water and lease it back ro irrigacors in difficu lt rimes.

Such schemes are entirely consistent with rhe principles of the marker.

Expanding the Market The marker can be exp anded co allow participation by large industrial water users char have traditionally placed a low value on the resource because it comp rises on ly a very small proporti on of their coral operating cost. When the p rice of water is cheap , the fina ncial drivers co either change existing behaviour or invest in efficiency works are low. The situatio n, however, changes if rhe saved water can fetch good prices on the marker.

A water marker may possibly include enviro nmental flow managers. Since Au gust 2005, the Victoria n Government has provided an extra I 0,000 ML in environmental flows for the Thomson River and an additional 17,000 ML will be p rovided co rh e Yar ra River. However, statutory al location s made by rhe Government in respect of environmental needs are a blunr cool char do nor allow rhe p roper trade-o ff between high and lo w value uses of water and, in a d ryi ng cl imate, is fra ugh t with tension from competing deman ds. A t rading system, with an environmental custodian acting o n behalf of a river, may be better placed to find the right balance. Prop osed addition s to rhe minimum passing flows can then be set up as a pu bl ic fund instead of in volu metric terms . Under such a syste m, rhe custod ian will be able to sell on rh e temporary marker, fl ows char at certain rimes of rhe year, exceed th e recommendatio ns o f scienti fi c sru dies while at ocher rimes, water may be purchased to satisfy h ighe r en vironmen tal objectives. This is a system able co incorp orate the value ch ar society places o n a healthy en vironment versus its own uses.

Recent Examples SA Water has bought more than 18 GL of ir rigation water (The Australian, 2 July 05).

The first p urchase resulted from lower M u rray irrigacors who, facing restructuring, approached the water uriliry.

SA Water described it as a win-win siruacion: rhe irrigacors earned enough money to upgrade their irrigatio n technology and SA Water increased its allocation . T he water h as been used for environmen tal purposes.

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Journal of the Australian Water Association

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In Western Australia, the Water Corporation is fu nding rhe piping of open irrigation channels in the Waroona and Harvey irrigation districts, curring delivery losses from 27% to 5% (Government of WA Media Statement, 13 May 2005). Eventually, rhis will allow the trade of 17 GL/yr from the consortiu m of irrigators known as Harvey Water to the Water Corporation. This is about 6% of the current usage of Water Corporation customers and is a crucial part of the company's total augmentation need of 107 GL/yr over the next five years.

In August 2005, Southern Rural Water auctioned off 790 ML of a new water entirlement that was created from water saved by replacing 4.5 km of old concrete irrigation channel in Nuntin with a new pipeline (The Weekly Times, 10 Aug 05).

Th is channel in rhe Macalister Irrigation D istrict was in such poor condition rhac up to 30% of the water was lost each season. Irrigators set a reco rd of $2400 pe r ML fo r the water right.

A 110 km pipeline connecting the city of Ballarar to Bendigo's Lake Eppalock and a 45km pipeline from Lake Eppalock to the Goulburn river system will be completed by 2008 to save these Victorian cities from run ning out of water. (Victorian Government, 2006) . Ir is proposed rhar 8- 10,000 ML/yr will be pu rchased from willing irrigators in rhe Goulburn system and up to 18,000 ML/yr to provide long term security fo r Ballarar. With the Goulburn-Murray system supplying about 1,000,000 ML/yr of high reliab ili ty entirlements fo r irrigation and other uses, the proposed connection will not appreciably affect rhe levels of service to irrigators.

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Rural- urban trading is one of the pillars of rhe N ational Water Initiative and is stro ngly supported by the Water Services Association of Australia. T he severity of the recent drought over much of eastern Austra lia has significantly increased pressure for water reform ro move in this d irection. The prospect of a drier cli mate combined with society's increasing expectations rhat environmental damage should be reversed or at lease ameliorated means that water is a more precious resource rhan eve r before. This concept of value can be translated into many styles of practical adaptation. At one end of the scale, there is the prospect of each co mmuni ty holding on to whatever

water it currently has from rhe accidents of history and being greatly resentful of any attempt at compulsory re-allocation.

At the other end of the scale, an enl ightened society wisely decides on the most beneficial uses of a scarce commodity fo r rhe widest good. W ater trading is a mechanism that can potentially move us all from one paradigm to another in a relatively painless and conflict free way.

The concept of urban-rural water trading is no longer the political minefield it once was. A group of business leaders involved in the food industry of northern Victoria recently proposed a plan to save 450 GL/yr by modernising the Goulburn and Murray irrigation systems with rhe help of investment from Melbourne and regional cities which would entitled them to a share of rhe savings (The Weekly Times, 21 February 2007) . This is an idea that may now be ripe fo r implementation.

The Author Dr Kein Gan is the Water SupplyDemand Manager in Yarra Valley Water, one of Melbo urne's retail water co mpanies, email kgan@yvw.com.au.

Part of this paper draws on wo rk undertaken for the Melbourne Water Supply-Demand Strategy in 2006. The views presented in this paper are nor necessarily chose ofYarra Valley Water.

References ACIL Tasman (2005) The Impacts of Water

Trading.

Australian Bureau of Statistics (2006)

Characteristics ofAustralia's Irrigated Farms, Dennis Trewin and Gary Banks.

Ausualian Financial Review (Oct 2006) Water Policy Reform is Long Overdue, Rod Sims, p.71.

Dept of che Prime Minister and C abinet (2006) National Water Initiative Water Trading Study, Report by Price WacerH ouse Coopers.

Harding S. and Viney B. A Study ofPotential

Savings in Northern Victorian Irrigation Distribution Systems, hccp://www.ancid. org.au/pdf/cd_pdfs/Viney_B.pdf Produccivicy Commission (2006) Rural Water

Use and the Environment: the Role ofMarket Mechanisms, Commonwealth of Australia.

T he CSlRO (2006) Without Water: The Economics ofSupplying Water to 5 Million More Australians, Policy and Econom ic Research Unit, CSIRO Land and Water, Mike D. Young, Wendy Proctor and Ejaz Qureshi.

V ictorian Govern ment (2006) SttStainable

Water Strategy Cemral Region Action to 2055.

Victorian Govern ment (2004) White Paper: Securing our Water Future Together.

4o

technical features .fereed paper

climate change

THE ENHANCED GREENHOUSE EFFECT: THREATS TO AUSTRALIA'S WATER RESOURCES PART 1: SCENARIOS FOR THE FUTURE AB Pittock Summary Scenarios or possible futures for climate in Australia, taking account of the enhanced greenhouse effect, go back more than 20 years. While advanced climate models can now quantify some of the uncertainties, the general picture has not changed much excep t that climate change seems co be happen ing faster than was expected. The scenario is bleak for water supplies in southern and eastern Australia.

Introduction Early scenarios of climate change for Australia (Pittock, 1980; Pittock and Salinger, 1982; Pittock, 1983, 1988} were based on general guidance from the p rimitive computer models of climate available in the 1980s. Regional detail was mostly based on analogies with previous warm periods such as ensembles of warmer or colder individual years or longer periods in the instrumental era, or warmer or colder epochs in the paleocli matic record. Simple dynamic arguments were also used, such as that Australian climate would be more like summer, with climatic zones moving further sou th and arguments based on an increase in poleward heat transport.

These various lines of evidence tended co suggest that global warmi ng would make for wetter co nditions where the summer monsoon affects climate in Australia, especially with an extension of tropical influences further south. There was also agreement that the mid-latitude westerlies, with the cold fron ts and low pressure systems associated with them, would be displaced further south, leading co less rain along the southern regions of Australia, especially in winter and spring. Uncertai nty centred on the likely changes on the ease coast and che role of the El Nino-Sou thern

Figure 1. Simplified schematic map showing th e major synoptic weather in fluences on rainfall in Australia. (Base map cou rtesy of the Bureau of Meteorology).

Oscillation (ENSO). T he rate of change was also highly uncertain.

A quarter of a century later the general picture has not changed much, with a stronger Australian mo nso on and the westerlies already further south. We are still unsure what changes might occur co ENSO , with the balance of evidence pointing to a somewhat greater likelihood of more severe, more frequent and longer lasting El Nifios and shorter La Nifias.

Evidence over che last three decades does suggest chat the climatic changes, and especially the impacts, are happening faste r than expected, with more severe consequences at an earlier dace, especially as regards rainfall and water supply. This paper reviews some of this evidence and discusses likely consequences.

The Australian Climatic Setting

A bleak scenario for southern and eastern Australia.

42 JUNE 2007 Water

Figure l shows the main synoptic weather influences on average rainfa ll patterns in Australia. There is the summer monsoon, driven essentially by the surface temperature

Journal of the Australian Water Association

differe nce between the Australian continent in summer and the land and water of the region of Indonesia and Southeast Asia.

T his causes a low pressure system co form over the Australian continent, bringing moist warm air south from across che Equator. Monsoon troughs, tropical lows and tropical cyclones can form over che Ti mor Sea, the Coral Sea and in the Gulf of Carpentaria in the summer half year and move so uth in to Western Australia, southern Queensland, New South Wales and sometimes even into northern Victoria, bringing storms and heavy rain.

To che south are the mid-latitude westerlies, with low pressure systems and cold fronts embedded in them. These are furthest north in winter, bringing win ter rain co the south coast and inland across the southeast in cut-off lows. When they are fu rther south than usual drough ts occur in che southwest and southeast of the mainland, and in northern and eastern Tasmania, but they may bring more rain co south-western T asmania.

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climate change

B .... • •. •.

The east coast is affected by the southeast trade winds in the northern parts and east coast lows that form in the Tasman Sea, and also by tropical cyclones that form off the Queensland coast and can move across the coast bringing heavy rains . Tropical cyclones can also originate in the Gulf of Carpentaria and o ff the northwest coast.

All of t hese rain-bearing systems vary from year to year. Norable is the variation known as the El Nino-Southern Oscillation (Troup, 1965; Pitcock, 1975; Nicholls, 1985; Allan et al., 1996; Chiew et al., 1998), which is a modulation of climate governed by regional contrasts between sea surface temperatu res and air p ressure across the tropical Pacific Ocean. Over many centuries this modu lation has sh own an irregular quasi-periodicity of some 3 ro 5 years due to internal oscillations in the climate system (Quin n et al., 1987; D'Attigo eta/, 2005; T udhope eta!., 200 1). T h ere appears to be an inter-decadal variation in the effect of ENSO on Australian rainfall, related to an inter-decadal oscillation in the tropical Pacific known as the Inter-decadal Pacific Osci llation or IPO (Power et al., 1999). In a La N ifia year there is higher than normal surface pressure over the tropical eastern Pacific, associated with warmer than normal sea surface tem peratures, and lower surface pressures and temperatures around I ndonesia and northern Australia. This sets up an air circulation that brings moist tropical air over northern and eastern Australia, with high rainfalls centred on New South Wales and southern Q ueensland in win ter and spring, and an intensified su mmer monsoon, with more tropical cyclones in the Australian region.

In an El N ifio year the opposite happens, with drier co nditions across t he same regions of eastern Australia, as has happened in che lase couple of years. It is important ro note that the ENSO cycle has relatively little impact on rainfall in the so ut hwest of Western Australia and in southern Victoria.

The Southern Osci llation index (SO I ), which is a crude measure of the state of the ENSO system, is the normalised p ressure difference between the eastern tropical Pacific, represen ted by T ahiti, and the western regio ns, represen ted by Darwin (Troup, I 965). Other indices of the ENSO system include sea surface temperature anomalies in defi ned regions, and differences between them , across the t ropical Pacific Ocean (Allan et al., 1996) . These d iffe rent ind ices of ENSO may behave di ffere n tly under climate change, as migh t climate change patterns associated with ENSO. Another variat ion to rain-bearing systems is caused by cha nges in the latitude of the westerl ies, and the related rai nfall patterns associated with what is called the Sou thern Ann ular Mode (SAM).

T his is a mode of variability of the extra-tropical climate system, in which su rface p ressure moves, more o r less symmetrically along each ci rcle of latitude, north o r sou th. During the positive phase of the SAM the circumpolar westerlies increase in strength and the circumpolar vortex co ntracts. This is associated with a pole-ward shift of the m id-latitude storm cracks and the related rainfall patterns (Cai and Cowan 2006; Meneghini et al., 2007; Hendon et al., 20 07). Figure 2 is a composite satellite photo sh owing the circumpolar vortex with the lows and cold fronts embedded in it, which b ring rain to southern Australia especially in winter and spring.

Changes in Australian Climate Since the l 950s G lobal average su rface temperatures have increased since preindust rial times by some 0. 8°C. There was a rapid increase in the 1920s and 1930s followed by some co oling in the 1950s and 1960 s, especially in the northern hemisphere. Globally temperatures have risen rapidly si nce the 1970s. The cooling after World War II was mainly regional around Europe, South and East

Figure 2. Photo-montage of satellite photos of the weather systems around the South Pole, showing the lows and cold fro nts that bring rain to south ern Australia. Courtesy of Burea u of Meteorology.

Asia and North America. Ir is thought to be due co the scattering of sunlight back into space by particulate po llutio n, mainly from the burning of sulphur-rich foss il fu els. T his led also to severe urban poll ution and acid rain, which was b rought under control in Eu rope and North America by switching to low-sulfu r fuels, or scrubbing the sulfu r em issions o ut of smokestacks. The rapid warmi ng since the I 970s is d ue to the ongoing accu mulation of greenhouse gases and the rapid reduction in the regional cooling by the particulates (IPCC, 2001 , 2007; Pitcock, 2003, 2005) .

G lobally, o bservatio ns of increases in atmospheric concentrations of carbon dioxide, global average surface temperatures, and sea level rise over the last two decades have all been tracking near the maximum of the range o f p rojectio ns from the 1990s made by the IPCC in 2001 (IPCC, 2001 ; Rahmstorf eta!., 2007). Possible reaso ns for this more rapid rate of climate change than genera lly expected are d iscussed below. In general, they are indicative of the likeliho od that some positive feedback or amp lifying p rocesses are not adequately represented in the climate and glaciological models.

In Australia, average daily maximum temperatures rose 0 .6°C fro m 19 10 to 20 04, and daily min imum temperatures l.2°C, with most of the increases since 1950 (Nicholls and Collins, 2006).

Wa rmings, as expected , have been greater inland in drier regions and away from the mod erating influence of the oceans.

Rainfall changes are shown in Figure 3, at left, for the period 1950-2002 as the observed trend in mm per year, and at right fo r the independent three year period February 2004 to January 20 07 as rainfall deciles. Note that in both cases dry ing is evident along the south coast of the main land and in northern and south-eastern Tasmania, and also up the east coast as far as the bottom of Cape York. Wetter conditions are evident in the summer monsoon region of northern Australia and in western Tasmania. The only major area where the two maps differ is in NSW and southern Queensland, where the effects of a strong El N ifio lead to rainfall deficits in the lacer period. While wetter conditions in the north and west of the continent have long been noted they were, until

Journal of the Australian Water Association

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JUNE 2007 43

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Figure 3. Left: Trend in annual total rai nfall (mm/yr) from 1950 to 2002. Right: Rainfall deciles for the three year period February 2004 to January 2007. In both cases, drier conditions are indicated by pink or red shading and wetter conditions by pale to da rk blue shading. (Maps cou rtesy of the Bureau of Meteorology.) recently, discounted because of the large year-co-year variations in rainfall char occur there. However, Smith (2004) argues chat ch e trends are now sufficiently large and extensive co be described as unusual in a historical context.

Figure 4 a shows a graph of the year-coyear fluctuations in the SOI index (chin line), alo ng with a five-year smooched version (chick line) to show che longer term trends . This shows large inter-annual fluctuations with a typical period o f several years. The smooched graph indicates chat over the lase three decades there has been a tendency for a more El Nino-like average (more negative values), with longer lasting El N inos and shorter La Ninas.

Explanation of Recent Trends Several regional trends are evident in Figure 3. T h e longer-term map, covering a lengthy period of strong global warming, shows: • a strengthening of the Summer monsoon (more evident in seasonal maps not shown here), • a drying trend in southern Aust ralia consistent with che westerlies trending further south (most evident in autumn and more recently also in winter), • and drying up the ease coast (less eviden t in maps starting earlier.

T he shorter-term map of the last three years (2004-2007) shows all these same features bur with the added strong drying in the main El Nino-affected region extending further inland in southern Queensland, all of NSW and northern Victoria. This suggests a contin uation of che long-term trend, with a strong El Nino drought pattern superi mposed.

44 JUNE 2007

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The trend in the summer monsoon was projected in the early regional climate change scenarios (e.g. Pitcock, 1988), and is due in pare co greater warming over inland Australia than over the oceans to the north (Wardle and Smith, 20 04) which have a greater heat capacity and thus warm more slowly. However, recent work by Rocscayn et al. (2006) suggests chat regional cooling effects of aerosols in southeast Asia may have strengthened chis tendency by increasing the temperature contrast with continental Australia. If so, any reduction in aerosols over southeast Asia in coming decades due co pollution controls may weaken chis rainfall increase.

The drying trend over southern Australia was first noticed in the southwest of Western Australia (Wright, 1974), where rainfall decreased by some 10 co 20% in the 1960s. Th is led co a 50% decrease in runoff into the Perch water catchment, vividly demonstrating che high sensitivity of runoff co warming and rainfall decreases. This decrease has been che subject of much research (Smith et al., 2000; IOCI, 2002) and is now attributed to a mixture of natural variability, che enhanced greenhouse effect and possibly in pare co the effects of stratospheric ozone depletion on che location of the westerlies (Hartmann et al., 2000; Marshall , 2003; Cai et al., 2003; Gillece et al., 2003). The lacrer is however problematic as the seasonality is wrong (unless there is a strong lag effect), with the ozone effect strongest in summer bur the rainfall decrease strongest in autumn and winter.

The mechanism seems co be primarily a strengthening of the SAM, which is clear in the observations and in climate simulations with increased greenhouse

Journal of the Australian Water Association

gases, although the observed effect is stronger than in che models (Gillece et al., 2003).

A similar trend in rainfall was first detected in rhe southeast of Australia in the 1990s and became stronger about 1997 (Wright and Jones, 2003), with a decade of below average rainfall in many areas si nce then. This has corresponded with an increase in mean surface pressures over southern Australia, and a decrease beyond 40°S. The d rying trend up che east coast has no well documented explanation , but could be related co a trend cowards more or longer-lasting El Ninos (more negative SOI), as is suggested by Figure 4a. This shows the Southern Oscillation Index (SO I), both on an annual and a five-year mean basis since 1880. There appears to have been a swirch to generally more negative values since 1976. Roger Jones (CSIRO, personal communication) finds chat a seep change in the SOI is statistically significant at the 90% confidence level (chat is, chat there is only a 10% chance chat it is a random variation). The step change is stro ngly evid ent in Darwin pressure but also in tropical Pacific sea surface temperatures (Ian Smith, CSIRO , personal communication). It is also coincident with the sudden decline in rainfall in the southwest of Western Australia (Smith et al., 2000; IOCI, 2002), although a reason for a link between che two is not clear. Such a seep change is not evident in ocher Australian rainfall records (Vives and Jones, 2005) in rhe 1970s. Ir is possible char gradual trends in radiative forcing could lead to seep changes in some regions but nor in ochers.

technical features (Gil

climate change The SOI correlates fairly strongly with rainfall in the Murray-Darling Basin (Figure 46, and Chiew et al., 1998; Power et al., 1999) although it explains less than half the total year-to-year variance. A similar but somewhat weaker correlation exists between the SOI and Victorian rainfall, but this is mainly due to correlations north of rhe dividing range.

The all-Victoria rainfall (Figure 4c) shows a declining trend in the 1990s and early 2000s rhar is steeper than rhar in rhe SOI, possibly reflecting the situation south of rhe dividing range where the influence of the westerly regime in winter is more important.

There are mulri-decadal variations in the relationship between ENSO (as measured by rhe SOI) and rainfall patterns over Austra lia (Power et al., 1998; Cai et al., 2001). Moreover, rhe situation along rhe east coast is complex, with claims that an observed strengthening of the southward flowing East Australian Current is due to a general srrengrhen ing of the oceanic gyres by rhe enhanced greenhouse effect and stratospheric ozone depletion (Cai et al., 2005; Cai, 2006) . Through local changes in sea surface temperatures, this may affect the climatology of East Coast Lows and tropical cyclones, both of which are major contributors to rainfall variability in this region . Clearly, fu rther work is needed to explain rainfall trends in eastern Australia.

Projections into the Future Nothing is certain about the future. Any projections are subject to a degree of uncertainty, and while some of these uncertainties are being reduced by further research or new information about actual changes and trends, we must treat the futu re from a risk management perspective. T his curs across the traditional "pure science" tradition of not asserting somethi ng as true unless it is likely at a 90% or higher confidence level. Risk management requires that we treat as important, possibilities which, while not highly likely, would have serious consequences. It is like insuring a house: we do it not because we thin k it will burn down next year, bu t because it just might, and we want to avoid the worst consequences of such a calamity, such as being homeless.

So it is with future climate. The above analyses suggest rhar, despite earlier dry periods, the present long "d rought" in southern and eastern Australia may well be part of a long term trend largely associated wirh the enhanced greenhouse effect, but with the added shorter-term effects of El Nino-induced drought in eastern Australia

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Figure 4. Plots of (a) the El Nino-Southern Oscillation Index (ENSO, the normalised surface pressure di fference between Tahiti and Darwin) , [b) the Murray-Darling Basin annual rainfall, and (c) the Victorian annual rainfall. Thin lines are the annual values and heavy lines the 5-year ru nn ing means.

no rth of the Victorian dividing range. T his view is strengthened by the emergence globally of a warming trend si nce the 1950s, indicating the growing effect of increasing greenhouse gas concentrations (I PCC, 2007) . If so, then these "drought" co nditions will likely continue as a more permanent climate change, with the possible exception of the El N ino affected area in southern Queensland, NSW and northern Victoria.

Even in the latter El Nifio-affecred region, rhe recent trend to more severe, longer and more frequent El Ninos might be partly attributable to the enhanced greenhouse effect. If so, then the El Nino-type drought area will have short respites as the ENSO oscillation continues, bur these respites will be short-l ived and insufficient to replenish water storages that in Australia typically require several years of above average rainfall to fill.

Further north and west, the trend to increased summer monsoon rai nfall may well continue, although this trend may be moderared by decreases in aerosol pollution in southeast Asia in coming decades. More frequent large-scale floods may thus be expected in these regions, exrending on occasions further south into southern Queensland, NSW and even northern Victoria (Pittock et al., 2006).

Amo ngst the key unce rtainties is the question of how soon and how serious the changes to climate will be. Here it is instructive to look at a number of factors that point to more rapid changes than have been projected based on existing cli mate models. These factors (Pittock, 2006) incl ude: • T he climate sensitivity (the stabi lised global warm ing due to a doubli ng of CO 2 in the atmosphere), which for more than a decade has been assumed to be in the range 1.5 to 4.5°C. The fact is that recent studies suggest it may be in the higher part of this range, well above 3°C (e.g. Annan and H argreaves, 2006; Heger! et al., 2006; Piani et al., 2005; To rn and Harte, 2006) .

• "Global dimming", or cooling due to particulate pollution, is decreasing. This has hidden some of the greenhouse warming, and now the full warm ing will become evident (An drae et al., 2005; Delworth et al., 2005).

• Permafrost is melti ng, leading to increased release of methane and carbon dioxide (greenhouse gases) from unfrozen peat bogs (ACIA, 2004; Nelson, 2003; Overland, 2006).

• Global biomass is turning from a sink or absorber of carbo n dioxide into a source, thus accelerating the greenhouse effect (Angert et al, 2005; Bellamy et al., 2005;

Journal of the Australian Water Association

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JUNE 2007 45

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climate change Canadell et al., 2007; Matthews et al., 200 5; Scheffer et al., 200 6).

• Arctic ice and seaso nal snow cover are d ecreasing rapidly, increasing absorption of sunlight (Co miso, 2006; Overland, 2006; Serreze and Francis, 2006) .

• Air and sea circulation changes are transferring heat to high latitudes more rapidly accelerating ice mass disintegration in G reenland and Antarctica (Cai et al., 2005 and 2006; Carril et al., 2005; Marshall et al., 2006) .

• Newly observed mechanisms are accelerating outflow glaciers in Greenlan d and Antarctica, including disintegratio n of floati ng ice shelves, surface melrwater penetration , and undercutting of tidewater glaciers ( those with valley fl oors below sea level). These are reviewed in Shepherd and Wi ngham (2007) who co nclude that "there are suspected triggers for the accelerated ice discharge . .. over the course of the 21 st century ... [and) these processes could rapidly counteract the snowfall gains pred icted by present coupled climate models."

Such mechanisms are co ntributing to the observed more rap id rise in sea level (Church and White, 2006) and to global warming near che maximum of the range of previous projectio ns by th e Intergovernmental Panel on C limate Chan ge (IPCC, 2001: Rahmsto rf et al., 2007). The IPCC in its 20 07 report on the science has noted so me of these effe cts but has not yet caught up with how serious this is, especially for sea level, which may well rise by more than a metre by 2100 (Rahmstorf, 20 07).

Australia?

Given the above caveats, which suggest that changes may o ccur more rapidly than climate model simulations presently indicate, what are the main trends affecting Australian water resources that are likely in the next cen tury?

Firstly consider the mo nso on. Projected warming seems likely to continue to warm the Australian continent faster than the seas to the north, thereby strengthening the driving fo rce fo r the Australian sum mer monsoon (Wardle and Smi th, 2004). H owever, there is the possible effect of the particulate pollution in sou theast Asia, which may well have reinforced the strengthening of the Austral ian monsoon in recent decades (Rotstayn et al., 2006, bu t see also Shi et al. , 200 7 who question thi s). If the particulate pollution over southeast As ia is reduced in future decades then this reinforcing effect may well d ecrease.

46 JUNE 2007

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However, this will take several decades, and meanwhile global warming is continu ing, so it is not likely that the monsoon will in fact decline in strength.

More likely it will continue to increase, but at a slower rate. Moreover, generally warmer air will have an increased waterbearing capacity (greater absolute humidity) and chus be capable of higher races of rainfal l. W e should therefore expect greater summer rai ns and greater flooding in monsoon-affected areas.

Co mbined with the expected further southward movement of the mid-latitude westerlies, this may also result in more intense summer outbreaks of tropical storms into more southern parts of Australia, with more fl ash flooding an d in some cases widespread basin floodin g where monsoon lows and trop ical storms penetrate further south (Pittock et al., 200 6).

As regards the south coast, the more southerly locatio n of the westerlies associated with a strengthening of the SAM, largely attributed to enhanced greenho use warming, is likely to continue, and indeed strengthen further. This is d espite the possibility of a slow recovery of the stratospheric ozone layer in h igh southern latitudes, since this effect on th e SAM is likely smaller than the potentially increasing effect of further global warming. Autumn, and also winter and spring rainfall alo ng the south coast is therefore likely to decrease fu rther.

M o re problematic is the expected change in rainfall in eastern Australia. If the trend in recent decades to a more negative SO I continues then rainfall is likely to continue to decrease, but with episodic returns to wetter La Nina conditions. Increasingly higher temperatures and evaporative losses, esp ecially in the summer half year, are likely to make drought conditions more acute in El N ino years, and reduce runoff in La Nina years even when rainfall is average or above. T his could however, be partly compensated for by more extreme rainfall in La Nina years due to generally higher temperatures increasing the waterholding capacity of the air masses.

Cl imate models remain ambivalent regarding the future behavio ur of the ENSO system. They all suggest that the oscillations will continue, bu t whether this will be about a more El Nino-like mean state is uncertain , with some models suggesting th is, and others suggesting the co ntrary (Cane, 2005; Joseph and N igram, 2006; Philip and van O ldenborgh., 2006; van Oldenborgh et al., 2005 ; Yamaguchi and Noda, 2006; Zelle et al., 2005 ).

Whatever the ch anges in the ENSO

Journal of the Australian Water Association

B - - --• •. • system, it is not obvious that a return to more freq uent La Nina events would relieve water shortages outside the main area of influence of ENS O , which does not include the south coast of Australia.

Most major Australian water storages are multi-year in capacity, and are intended to tide water supplies over multiple drought years. T his means that t hey do not in general refi ll in one or two years of average or above average rain, but rather respond to long-term trends by integrating runoff over a number of years. T his makes them quite vulnerable to long-term trends such as a trend to increased evaporative losses d ue to global warmi ng (Nicholls, 2004), desp ite high year-co-year variab ility in rainfall.

Rapid sea level rise will also adversely affect freshwater resources by increasing salinity in estuaries and groundwater in coastal margins, leading to less reliable groundwater extractio n in populated coastal areas.

Conclusion Climate change and sea-level rise are already happening in a way broadly consistent with our understand ing of the potential impacts of increasing greenhouse gases in the atmosphere, albeit somewhat faster than expected. This is already having large effects on water supply in Australia.

Although uncertain, reasonable projections suggest chat the situation will get worse, especially in southern Australia and very possibly in eastern Australia also. A switch from an El Nino to a La Nina will nor solve all our water supply problems, as it will be at best short-term and will likely have relatively li ttle effect on many coastal cities and on longer-term water storages.

Part 2 of this paper will discuss further the projected impacts of climate change in relation to Australian water resources, and what might be do ne ab out it.

Acknowledgments Thanks are due to the Chief of CSIRO Marine and Atmospheric Science fo r continuing my Honorary Fellowship, and to Tim Cowan of CSIRO for help with Figures. I also wish to thank Wenju Cai , Roger Jones and Ian Smith of CSI RO for their critical com ments which have been most helpful.

The Author Dr Barrie Pittock is an H onorary Fellow CSIRO Marine and Atmospheric Research. H e retired in 1999 as Leader of the CSIRO Climate Impacts Group, and was awarded a Public Service Medal. H e is the author of Climate Change: Turning Up

the Heat (CSIRO Publishing, 2005), email: bpiccock@bigpond.com; barrie.piccock@csiro.au

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climate change Hendon, H .H., Thompson, D .W.J., and M.C. Wheeler (2007), Australian rainfall and surface remperacure variations associated wirh the Southern Hemisphere Annular Mode. /.

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Pircock, A.B. (1983). Recent climatic change in Australia: implications for a CO2-warmed Earth. Climatic Change, 5, 321-340.

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Pirrock, A.B. (2005). Climate Change: Turning Up the Heat, CSIRO Publishing, 3 16 pp.

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.....

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THE ECONOMICS OF SUPPLY AND DEMAND OPTIONS: PROBLEMS WITH LEVELISED COST R Beatty, S O'Brien Abstract

Initial Workshopping

Screening Criteria • Environmental • Social • Economic ~

The idea that the economic assessment of all supply and demand options can be undertaken with the universal application of Levelised Costs (so called Least Cost Planning approaches) is an oversimplification of the Integrated Water Reso urces Planning process. Ir can lead to the si tuation where a sub-optimal portfolio of demand and supply options is presented as the preferred option without due consideration of the environmental , social and economic impacts.

/

Goal setting ~ Identification of long list (supply and demand options) Coarse screening

Supply Option Assessment • Cost • Environmental • Social

Demand Analysis • Climate correction • Sector analysis • NRW assessment

Demand Option Assessment/

End Use Model

Ranking • Water savings • Treatment and transfer savings • Capttal delay/downsizing • Hot water/emissions savings

Development

+- •Breakdown in use • Demand drivers • Baseline forecast

+ +

Selection of Preferred Supply Option

Scenario Building/ Bundling of Measures

• Examination of trade--0ffs/ • Revision of goals ~

Introduction

Assessment of Scenarios

In the evaluation of the economics of demand management and water supply ampl ification options, a range of economic evaluation approaches have been used. T he concept of"Levelised Cost" is increasingly being used to evaluate the cost-effectiveness of supply and demand management options in IW RP efforts.

Fane and White (2003) define "Levelised Cose" as the opportunity cost of capital divided by water savings discou nted in the same manner as the coses: '

c = V ,L

I

_LC,, (l +r);; _11_ =1_ _ _ __ I

I

.Z: v,, o+ r i it=!

• Water savings .__ _ _ _ _ _ • Treatment and transfer savings • Capital delay/downsizing • Hot water savings / Opportunities for ~ stakeholder input

Selection of Preferred Scenario - - - - - - • Examination of trade-offs / • Revision of goals ~

This discussion paper ourlines a number of concerns about rhe application of the Levelised Cost for mulation in the comparison of rhe cost-effectiveness of supply and demand options.

Levelised costs calculations lack assessment of avoided costs.

~-----------

Figure 1. A Typica l Integrated Water Resources Planning Methodology.

What is the Levelised Cost?

T he concept of levelised cost has it's origins in the concept of Average Incremental Cost (AIC) which is derived from rhe need to equate the unit cost of an irem for which the revenue equals total costs in the long run. This can be expressed as: r

I

t

The authors suggest chat the discounting of rhe water savings with rime rakes account of rhe time preference for rhe utility provided by water use. T hus it is implied char warer saved earlier results in improved cost effectiveness.

Compatibility/ Interaction of Measures

_L AIC,,x V,,(l + r) ;; n=I

I

= _LC.(l+ri n=I

Because the AIC is constant at every rime step we can rearrange the fo rmula to: I

1

I

I

= _L C.(l +r) ;;

AICX _LV. (l +r);;

11=1

n•I

Thus our formula for AIC becomes: r

I

_LC,,(l+r) ;;

AJC = .:..:"-= s 1_ _ _ __ r

I

L v.(l + ri

speaking, the term "cost" is a little misleading. In an IWRP context, the AIC should be seen as the volume-based revenue required to recoup a capital and operational outlay over rime. The suggestion that the denominator of the equation represents an eco nomic utility associated with the rime preference of consu mption is simply incorrect. The discounted water savings represent the volumetric component of the opportunity cost associated with revenue flows.

T he AIC approach has been used previously in the assessment of the Average Incremental Cost for whole supply systems (Warner 1996). This application to full supply systems is nor being addressed or critiqued here, bur rather the application for comparison of supply and demand op tions in an Integrated Water Resources Planning (IWRP) framewo rk.

n=I

which is the Levelised Cost fo rmulation ourlined by Fane and White. Conceptually

There are a number of examples of the appl ication of Levelised Cost to assess demand management and supply

Journal of the Australian Water Association

Water

JUNE 2007 49

technical features

demand management amplification options . One recent example was in a review of the supply and demand options for South East Q ueensland (ISF and Cardno, 2007).

What is Integrated Water Resources Planning?

IWRP involves rhe assessment of a range of supply and dema nd management measures in the planning for future water supply security. To chat end , IW RP requires a planni ng framework char fac ilitates nor only the con sideratio n of the costs and benefi ts of optio ns, bur also rhe trade-offs between the various environmental, so cial and economic outco mes inherent in different water futures (Figure 1) . The IWRP framework needs to be flexible, allowing the level of focus and effort to be reduced to an ap propriate scale when planning for smaller communities . Ir also n eeds to lend itself to the engagement of stakeholders, which is an essential part of inregrared planning across all areas of urban infrastructure, no r just water.

The framework has four key elements:

• Understanding ofdemand drivers. Ir is essential char the many and varied influences on water demands are well understood.

• Estimating the impact ofdifferent demand management and source substitution options.

This is best accomplished with rhe use of an end use model, where estimates of the water use against "end uses" in each sector can b e m ade. End use models differ from traditional "top down " forecast ing models in char rhey generate forecasts by summing up component end uses.

• Assessment ofsupply options, which involves a consideration of the environmental, social and economic outcomes associated with each; and

• Assessment ofscenarios. T his involves examining the en vironmen tal, social and economic outco mes associated with different bundles of demand and supply options; including the examination of the trade-offs between competing outcomes.

Allowing stakeholders to examine a number of different water futures provides the best mechanism whereby trade-offs b etween coses and outcomes can be examined (Figure 2 ).

The approach where all demand and supply options are assessed with a simple costeffectiveness fo rmula (so called "Lease Cost Planning" approaches) are an oversimp li fication of rhe level of sophistication requi red in gen uine IWRP efforts.

50 JUNE 2007

water

Net Economic Impact

Environmental Benefit

Env. Benefit -,,.Extraction 1' Water quality -,,. Emissions

Zero

Level of Investment

Figure 2. Impacts from Increasing Levels of Integrated Water Cycle Management (Beatty, O'Brien and Stewart, 2005).

What are the Problems with Levelised Cost?

There are significant problems with rhe application of Levelised Cost in an Integrated Water Resources Planning Framework. Issues relate to the application of rhe Levelised Cost model and the inherent bias in rhe resulrs ir produces.

Some of these problems are illustrated in rhe examples set our below.

The failure to recognise the planning context

If we examine the planning context of decisio ns abou t demand management and supply augmentation options, we appreciate char the coral cost of any portfolio of options will b e dependent on a complex interaction of costs and avoided costs (benefits). The d emand forecast will determine the timing and sizing of capital expenditure and the costs of the rrearment and transfer of both potable and recycled water. Calculation of rh e total net cost may also need to rake into account changes in outcomes from carbon and water trading and savings to customers from reductions in energy use associated with rhe hearing of water.

T he Levelised Cose formu lation h olds rhe inherent assumption char there will be a stream of revenue resulting fro m the implementation of a measure. Indeed there will be a stream of avoided co ses (e.g. capital, treatment, transfer and water hearing) accompanying rhe implementation of a demand management measure. These costs are nor considered in the Levelised Cost calculation. lf we rake a simple example of a water supply system with a current avoided costs

Journal of the Australian Water Association

of $0.30 per kL and a future supply amplification with a Levelised Cose of $ 1.00 per kl. (Note chat the current system avoided coses will increase as che time for the amplification of rh e supply system gets closer). In a Least Cose Planning approach, all demand management measures with a cost less char $1 .00 per kL would be recommended fo r adoption. However if the current avoided costs are only $0.30 per kL, then it is nor cost ben eficial for a measure to be implemented unless the cost is below $0.30 per kL. In this context, rhe idea chat decisions on rhe implementation of options can b e made o n the basis of Levelised Co se is an over si mplification of che economics of rhe management of supply, demand and avoided coses.

Bias generated from the profile of water supplied of saved The application o f the levelised cost form ulation to d ifferent profiles of water saved can result in b iases in cosceffecciveness outcomes. As an example, consider three different demand management o r supply amplification profiles with identical present values of cost, bur with different water savings profiles (Figure 3). A falling water savings profile is typical of some retrofit programs such as ch ose for dual flush to ilets, where che comparison of rhe amount of water saved with the business as usual case will fall over rime due co rhe expected narural increase in the p roportion of dual flu sh toilers char would occur in any case. The relatively constant level of water savings would be typical of a leakage reduction or community education program. The increasing level of water savings would be

technical features

typical of a measure that targeted new development such as the mandatory installation of water efficient fixtures, dual reticulation or rainwater ranks.

• Identical NPV of Costs • Identical Total Volume of Water Saved

If our goal is co free up supp ly capacity at some p oint in che future then the Levelised Cost a pproach gives us a misleading picture of cost effectiveness. Indeed ic is not hard co imagine circumstances in wh ich the adoption of some measures with a low Levelised Cost could actually result in an increase in the coral cost of a portfolio of options.

The failure to apply a consistent time period to the analysis O ne of the common p itfalls in the application of Levelised Cost is the failure co apply a consistent time period co che analysis. As an example, co nsider a supply ampl ification costing $ 1,000,000 (in teal terms) in the year of amplification with an ultimate volume of water supplied of I 00,000 ML/an num (Figure 4). If we exam ine the Level ised Cost of each option, with the calculations undertaken in all cases over years I co 30, we can see that the cost effectiveness is biased by both the t im ing of the initial capital o utlay and the time period for the esti mation of the water supplied.

The Levelised Costs are: • pushed down due to the delay in capital investment and • pushed up due to the failure co accou nt fo r the fu ll period of water supplied in the discounted water supplied.

This illustrates an important point - that if we are to compare supply and demand options using Levelised Cost - we must assume that all options are implemented in year zero. T ypically practi t ioners u se a fixed time frame for the calculations with the date for the introduction of the supply measures being determined by demand triggers.

Time Figure 3. Levelised Cost Outcomes for Different Water Savings Profiles.

manner, the Levelised Cost formulatio n does not include enough information o n avoided costs to serve as a basis for decision m aking. If our goal is to generate water savi ngs in the medium and lo ng term, then it may be more appropriate to use the formulation wh ich provides and indication of water saved in a particular year rather than use the Levelised Cose formulation which rewards water savi ngs in rhe near term and penalises those in che m edium an d long term. Biases can also be generated in the use of a fixed time frame for an analysis.

Due to these shortcomings ir is considered that Levelised Cose is an inappropriate form ulation for use in the comparison of supply and demand op tions. It is an economic model applied in the wrong context.

The examples above provide us with important information about what we are measuring when it comes co costeffectiveness formulat ions. If our goal is to provide water savings in a cost effective

T he best approaches fo r compari ng options are those which simulate the costs and water supply security over time. The most common approach is to examine the total NPV of different bundles of supply and demand options, each of which provides long term security of supply. If comparisons are to be made of individual op tions, then the comparison should adopt: • Cost effectiveness indices that do not introduce unwanted biases in the results of the analysis, i.e. the annualised cost or the Levelised Cost concept as defi ned by Dziegiliski et al (1993); • Benefit cost analysis (benefits of avoided costs divided by cost of demand management measures); or • Total system simulation .

Impact of Time Frame on Levelised Cost Outcomes (Fixed Time Frame) Fixed Analysis Time Fram e

100,000

An inappropriate evaluation approach We have seen above that, mathematically speaking, the concept of Levelised Cost (Average Incremental Cost) is correct and useful in estimating the constant cost per unit volume required co cover costs over time. The analysis of the p roperties of the Levelised Cost formulatio n however, clearly shows that it m ay provide results that are inappropriate in the IWRP context.

What are the Alternatives?

£llil

:¥

Year of implementation: 1 NPV of costs:S934,579 NPV of water savings: 444,603

80,000

a.

C. :,

Levelised cost: $2 .10 - - ~ - - - - -

II)

,S ~

60 ,000

0

~

Year of implementation: 21

40,000

NPVof costs:S241 ,513 NPV of water savings: 115,797 Levelised cost: S2.09

:,

~ 20,000

0 0

5

10

15

20

25

30

35

40

Year of Implementation

Figure 4. Impact of Time Fram e on Levelised Cost Calculations.

Journal of the Australian Water Association

water

JUNE 2007 51

technical features

demand management Different supply options have rheir own complexities with economic, social and environmental impacts . Decisions on the supply options need to be made th rough the examination of the trade-offs inherent in each op tion, resulting in rhe adoption of a preferred supply strategy. Considering both supply and demand management options in simple cost effectiveness framewo rk is both an over simplification of rhe IWRP process and lacks transparency.

Stakeholders need to be presented with a number of differen t portfolios of demand management and sup ply measures, where rhey can examine the trade-offs inherent in each before coming to a conclusion. Thus the authors would strongly recommend that supply measures be evaluated in a separate framework to demand measures and that once a preferred supply strategy is developed, the impact of increasing levels of demand management on rhe total costs of supply (either the Net Present Value or some measure of the long-run marginal cost).

A key aspect of IWR P approaches is that stakeholders are presented with a range of different portfolios where they can understand the rrade-offs economic, social and environmental trade-offs inherent in each (Figure 5), nor a single "Least Cost" solutio n.

Cost per unit volume approaches, of which Levelised Cost is just one variant, should no t be used for anything other than a coarse screening tool fo r different demand management options. Even then, practi rioners need to be aware of the properties of rhe type of cost effectiveness formu lation being used and the potential for a biasing of results. These approaches should not be used for a co mp rehensive evaluation of supply and demand options.

....,,coo 1">,COO

300,000

""¡""

100,000

"¡"'° Yu,

Figure 5. Impact of Demand Management of Supply Amplifications.

Association (AWWA 20 06) advocates the use of Benefit Co se analysis approaches.

T oral system scenario plan ning appro aches are important at rhe regional scale to understand the dynamics of water demand supply systems. Climate d riven variations in both the replenishment of supply so urces and demand are simulated to understand rhe reliability of the system as a whole.

T his type of simulation is particularly important when assessing the effectiveness o f rainwater ranks, wh ich have the advantage of supplying water from small rainfall events char typically do not provide

significant replenish men t to groundwater and surface water sup plies. In ad dition , due to the spacial separation of urban areas and catchments, as a distributed source rainwater tanks often provide water when surface and groundwater catchments are in d rought, and vice-versa. This increase in the reliability of rhe supply system as a whole means chat the cost effectiveness of rainwater ranks can be assessed from a total system perspective and not on the basis of the "one house, one rank simulations chat are typically undertaken. Examples of chis total system simulatio n wo rk can be found in Coombes et al (20 02 and 200 3).

Benefit cost analysis approaches examine the benefits accruing to both the water utility and the wider community from avoided capital, operating and water heating coses and the costs associated with the implementation and sou rce su bsricurion efforrs (Figure 6). The advantage of this approach is char it seeks co simulate che operation of a water su pply system over nme.

There are a number of examples of the applicatio n of benefit cost analysis (Beatty, Chapman and Maddaus 2002, Montgomery Watson, 2000) and che end use model used in the NSW Integrated Water Cycle Management program has an in-bu ilt module for calculating avoided costs (DEUS 20 05). T he recencly released Water Conservation Programs Planning Manual of the American Water Works 52 JUNE 2007

water

Figure 6. Factors Considered in Benefit Cost Analysis.

Journal of the Australian Water Association

Conclusions While the concept of Levelised Cost has some application in the assessment of long run marginal coses of water supply systems as a whole, it is inappropriate for use in che comparison of different demand management options. Levelised Coses calculations lack a planning context for the assessment of avoided costs and may bias che cosc-effecriveness calculations co favour options which have water savings profiles char are incompatible wich our water resources plan n ing goals.

The idea char che economic assessment of all supply and demand options can be undertaken with che un iversal application of Levelised Coses (so called Lease Cose Planning approaches) is an oversi mplification of the lnregrared Water Resources Planning process. le can lead to che situation where a sub-optimal portfolio of demand and supply options is presented as the preferred option without due consideration of che environmental, social and econo mic impacts.

In many ways ic would be desirable co have a more simple approach.

Incegraced Water Resources Planning exercises are derailed in their need co consider a much wider range of alternatives char traditional wacer supply plann ing approaches. T he widely recognised need to undertake fucure water resources planning in an integrated manner means char rhe planning process will be more involved and will requ ire che engagemenc of stakeholders. T his is in concrasr to the simpler and less co nsultative approaches char we have used in rhe pasr. Unforcunarely che use of Levelised Cost to examine demand and supply opti ons in a single eco nomic framework does not provide us with a valid methodology for simplifying our Incegrated Water Resources Planning efforrs.

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The Authors Russell Beatty is Leader Water Sustainability with MWH Australia (russell. beatry@au.mwhglobal.com) and Shane O'Brien is Principal Planni ng Engineer with MWH Australia.

Pista 360°

References American Water Works Association (A WWA) 2006, Water Conservation

Programs -A Planning Manual - Manual of Water Supply Planning Practices M52.

Bearry R., Chapman S ., Maddaus W., Benefit Cost Analysis with an End Use Model, A WWA Water Sources, Las Vegas, January 2002 Beatty, R., O'Brien, S. and Stewart, B., (2005). Integrated Water Cycle Management - Getting the Economics Right. Ozwater Watershed, May 2005.

Coombes P.J., G. Kuczera, J.D. Kalma and J.R. Argue. An evaluation of the benefits of source control measures at the regional scale. Urban Water.

4(4). London, UK. 2002.

Coombes P.J., and G. Kuczera. Analysis of the performance of rainwater ranks in Australian capital cit ies. Proceedings of the 28th International Hydrology and Water Resources Symposium. Wollongong, Australia.

2003.

Department of Energy, Utilities and Sustainability (DEUS), 2005, NSW,

Tertiary Treatment • Microfilters to 5 micron • Berson Ultraviolet Disinfection

Demand Side Management least Cost Planning Decision Support System, June 2005 Dziegielewski B., Opi tz E. , Kiefer J., and Baumann D. (1993), Evaluating Urban Water Conservation Programs: A Procedures Manual, A WWA Carbondale IL, USA. Fane, S . and White, S. 2003, Levelised cost, a general formula for calculations of unir cost in integrated resource planning, Efficiency 2003 : Efficient Use and Management of Water for Urban Supply Conference, Tenerife, 2-4 April 2003 . lnsriture for Sustainable Futures (ISF) and Cardno, 2007, Review of Water Supply-Demand Options for South East Queensland, February 2007 Montgomery Warson, 2000, improving Water Use Efficiency in Queensland's Urban Communities, report prepared for the Queensland Deparrmenr of Natural Resources, November 2000 Warner, R, 1996, Water Pricing and the Marginal Cost of Wate1; Urban Water Reseai-ch Association ofAustralia, Occasional Paper No. I, December 1996

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Journal of the Australian Water Association

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JUN E 2007 53

technical features

THE BRISBANE AQUIFER PROJECT P Evans, N J Arunakumaren, A Moore JEHA ·.

Introduction At the time of preparation of this abstract the catchment areas of the major water supply storages in South East Queensland remain in rhe grip of one of rhe most severe droughts in over a centu ry. Brisbane City Council has been addressing rhe water shortage through a range of water saving and water p roduction initiatives, o ne of which is the Brisbane Aquifer Project.

T he Brisbane Aquifer Project initially aims to produce 20 ML/d of groundwater to provi de supplementary town water supplies for Brisbane City. The project is being del ivered in rwo main phases. The initial phase of rhe project to establish a series of up to nine borefi elds across Brisbane has been accomplished as a partnership between specialist hydrological consulting firm EH A and the water supplier fo r Brisbane C ity, Brisbane Water. The requ ired exploration and production bore d rilling and testing services have been supplied by p rivate sector contractors with assistance from the Queensland Department of Natural Resources and Water. The second phase of the project to deliver borefield water treatment plants and associated power and reticulatio n is currently being achieved under an alliance structure with Brisbane Water, MWH Australia Pty Ltd and Aquatec-Maxcon Pry Ltd together with a series of sub-alliance partners.

Brisbane Aquifer Project Aim The aim of rhe Brisbane Aquifer Project is to obtain supply of 20 ML/d for mainly potable supply with a 3- 5 year timeframe to assist in the current drought situation and comply with the legislated direction.

T he key elements of the project are:

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• Undertake a parallel process of investigation, d evelopmen t and assessment aquifer systems in Brisbane City;

Figure 1. Typical production bore construction in Tertiary age sediments.

• Development of decentralised water treatment and infrastructure to allow injection into existing water supply system;

adap tive management framework to manage rhe resource;

• Collection of suitable baseline data and execu tion of supporting environmental and hydrological monitoring to support an

The Brisbane Aquifer Project is one of the ways Brisbane is boosting its water resources.

54 JUNE 2007

Water

Ptter Evans

Qt.TE COM'LETEO: 261(11(2(»6

TOTAL DEPTH: 137 REFERE~EPOINr: Gl. NATUFW. SlffACE ELEVATION (rrAHO): 6631 9111.(mbGL) : 27A5 M!asorernert Om: 06/11/2006 EASIING: 5100<!8.154 ~RTHNG: 694)909.129 Coord ~ w:;~

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Qt.TE STARTED: 201(11(2006

REGISIEREO ~: ORIWNGCONTAACTOR: ORILUNGI\/ETHOO: ORIWNGEQUIPMNT: 9M'IJNGI\/ETHOO:

Ganvna (API)

Brisbane Aquifer Study· Phase 2

• Review of hydrological and environmental impact and resource sustainability; and • Potentially development o f artificial recharge to augment sustainability

Brisbane Aquifer Project Team The key to the implementation of the Brisbane Aquifer Project to date has been the coordination of a large mult idisciplinary ream as follows:

Journal of the Australian Water Association

• Brisbane Water (client) - project management, logistical support, development of operation p lans; • EHA Pry Led - hydrogeological planning, supervisio n, analysis, support for environmental planning; • Brisbane City Works (BCC) - logistical support (s ire set up, water management and rehabilitatio n); • City Design (BCC) - environmental management for construction and op erations, town planning support;

technical features lfereed paper

• Marcom - community consulcacion support in conjunction with BCC staff; • Safe-T-M an (Les Norton) - safety management;

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Brisbane Aquifer Project Background Planning One of the key features of the Brisbane Aquifer Project has been the detailed backgrou nd plann ing chat has preceded the field implementation activities. T his background planning has included a detailed review of historical geo logical and hydrogeological reporcs (mainly 1950s and 1960s vintage) and drill core held at the Geological Survey of Queensland Explorati on Data Centre; review of historical hard-copy and electronic fo rmat Q ueensland Department of Natural Resources and Water (NRW) reco rds and discuss ions with key NRW staff; detailed discuss io ns with key water boring co ntractors; and a program co locate, test and sample key existing water bores.

Armed with considerable hydrogeological and geo logical knowledge obtained from these preliminary processes preliminary hyd rogeological targets were developed. A systematic process followed, chat in volved che comparison of likely hydrogeological targets with GIS coverages of parcels of BCC owned land, land parcels listed on the Queensland Environmental Protection Agency (EPA) Environmental Management Register and sites recognised co hose weclands associated with signi ficant groundwater discharge.

O nce che revised targets we re developed, an additional systematic process was undertaken co rank the key sites (groundwater development units) based on likely yield, vo lume likely co be available, and groundwater quality. A key requirement in che development of borefield targets was a pragmatic economi c criteria chat no bore should yield less than 5 Lis and no borefield should yield less than 25 Lis. Once che targets were refined a process of prelimi nary costing and scheduling was undertaken adopting reasonable success rares in the various areas

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• Drill ing contractors (five separate operations including the Q ueensland Department of Natural Resources and Water); • Test pumping contractors; and • Des ign and construction Alliance (Brisbane Water, MWH Australia Pcy Led and Aquacec-Maxcon Pcy Led) - des ign/ delivery of bore pumps, reciculacion, water treatment planes and control systems

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• Brisbane Water SAS Laboratory - water sampl ing/analysis;

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Because of limitations in available data regarding aquifer recharge and discharge rares, wherever possible and practical, deeper aqui fe r systems co nsidered co have more limited hydrological linkages co local streams and wetlands have been targeted over shallower, more intimately connected systems

Brisbane Project Raw Water Source Development Process Exploration and development drill ing was commenced in March 2006 and che production bores were completed and tested by che end of February 2007.

T he raw water source development process essentially consisted of the fo llowing processes:

• Drill rest holes and geologically and geophysically log che holes co confirm aquife r identity, geometry and lich ology (including target water bed grain size from sieve analysis of disturbed samples); • Where appropriate case che test holes with 50 mm diameter uPVC casing and ai rl ift pump/free flow che observation bores co obtain preliminary assessments of aq uife r yield and salini ty;

• If che hydrogeological data from che test holes was fa vou rable, drill production bores with screen locations determined from the logs and screen sizes from analysis of the sieve analysis data; • Com piece che production bores with suitable casing (uPVC or steel in diameters general ly rangi ng from 152 - 203 mm), gravel pack, and annular seals and grouting and airlift pump to remove fines from the gravel pack and screens and provide additional assessment of yield (usually

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Journal of the Australian Water Association

water

JUNE 2007 55

technic~I features t ,fereed paper

discharging over a rectangular or v-notch weir board); • Run in a test pump and undertake a scoping test for 60 - 120 minutes duration analyse the scoping test data and select a suitable test rate for lo ng-duration testing; • Undertake 100 hour test pumping whilst measuring groundwater levels in the pumping bore and observation bores, collecting routine water quality samples and continually monitoring pH, temperature and salinity using in line instruments and data loggers;

i

1.

• Analyse the test pumping data to select initial design production rates appropriate bore spacings; • Collate test pumping data for all bores within a target borefield area including gro undwater quality; and • Undertake analytical modelling to support determination of final design borefield rates.

Figure 1 provides an example of the construction of EMKl 00-P, one of the production bores tapping water beds of the Tertiary age Darra Formation at Eight Mile Plains. Figures 2 and 3 provide a summary details for the test pumping of bore EMKlO0-P. Figure 4 provides a schematic geological cross section indicating the location of bore EMKl 00-P. Figures 1 and 4 illustrate the value of routine use of down-hole geophysical logging (gamma, point resistivity and self potential) to support aquifer water bed identification and defin itio n and ready

**

....

-

-.......

Figure 4. Schematic geological cross section in Eight Mile Plains North borefield area. hydrogeological correlation between boreholes to assist in aquifer boundary defi nition.

It should also be noted that Brisbane City Council and Brisbane Water are very cognisant of the linkages between groundwater systems and su rface water and wetland systems and in co njunction with the implementation of the aquifer project have initiated a environmental assessment includi ng monitoring of flora, fauna and hydrological conditions to support a process of ongoing adaptive management.

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The treated water supply development process is not addressed in derail herein, suffice to note that an Alliance team was formed to build on preliminary work by Brisbane Water to develop reticulation, treatment, operation and controls fo r the borefield. The design of water treatment process and the co ntrol systems has included but not necessarily been restricted to filtrat io n, pH correction , aeration, iron and manganese removal, disinfection, blending into mains and reservoirs to achieve salinity targets.

Brisbane Aquifer Project Key Challenges

BCC borefleld

_,

56 JUNE 2007

Brisbane Project Treated Water Supply Development Process

Journal of the Australian Water Association

The key challenges for the proj ect to dare have revolved around the execu tion of a major groundwater investigation, development and assessment program and approval process in parallel and against a tight timeframe. These challenges have been compounded by restrictions associated with working in an urban area such as ensuring protection of key surface and subsurface infrastructure, management of sire access and safety management, management of water and drilling wastes (cuttings and mud) and site rehabilitation.

T he key to addressing these challen ges has been to identify the key issues and appropriately plan and resource management activities whilst actively undertaking communication with potentially impacted stakeholders. In addition, prior to commencement of drilling, a formal process of site clearance is undertaken to ensure th at sensitive

technical features ?fereed paper

Table 1. Summary of borefield development progress.

Borefield area

Geological Target Bore depth age of target formation/s range (m) formations

Nature of aquHers

Number of production bores proposed to be ooerated

Approximate target borefield yield (MUd)

GroundWater electrical conductlvlty range (ÂľSiem)

Comment

3

2.59

240 - 370

Bores completed & tested

Unconfined / 21.5 ¡ 24.5 semlconfined sands & sandstones

Sunnybank

sunnyt>ank Formation

Tertiary

Calamvale

Darra Formation

Tertiary

52.0 - 106.0

Confined sands & gravels

4

2.16

590 - 900 (blend 670)

Bores completed & tested

Runcorn Eight Mlle Plains south

Sunnyt>ank Formation, Corinda Formation.

Darra Formation

Tertiary

24.5- 138.0

unconfined I semiconfined I confined sands, gravels & sandstones

6

5.96

150 - 1,280 (blend 450)

Bores completed & tested

Eight Mlle Plains North

Darra Formation

Tertiary

119.0 - 130.0

Confined sands & gravels

3

3.11

150 - 610 (blend 335)

Bores completed & tested

Forest Lake

Woogaroo Sub-Group

Mesozoic

120.0 - 149.0

Semi-confined / confined fractured sandstones

3

2.59

930 - 1,600 (-1,300 blend)

Bores completed & tested, blending of groundWater Into reservoir required

Chandler

Neranlelgh Femvale Beds

Semi-confined / fractured metasedlments

7

4.23

680 - 2,200 (-1 ,230 blend)

Bores completed & tested, blending of groundWater Into high-capacity main required

Darra

Darra Formation

0.52

400

Tanker stallon commlslsoned

Palaeozoic 120.0 - 173.0

Tertiary

41.0 - 100.0

Confined sands & gravels

vegetation and underground services are not damaged.

T he coordination of the site management teams and the coordination of up to fi ve drillers and two test pum ping crews simultaneously has required regular (weekly-minimum) fo rmal project management planning meetings incorporating the use of "live" electronic format GIS and sched uling tools to allow rapid assimilati on of issues across the supporting multidisciplinary team. T his has substantially overcome stand-by delay costs fo r drilli ng contractors.

T he key technical challenges for the raw warer sou rce development portion of the project have involved the prevalence of artesian conditions in some areas of the Tertiary age Darra Formation where significa nt heads have developed in confi ned aquifers (up to 9.5 m above ground level). The presence of artesian conditions complicates the construction of both investigation and production bores with carefu l weighting of drilling muds being required to overcome aqui fe r pressure in relatively shallow bores (circa 100 m compared to typical Great Artesian Basin aquife rs which are many hundreds of metres d eep). Such bores have req ui red annular cementi ng to allow control of flows with bore construction supervised by drill ing supervisors holding Class 3

~

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Journal of the Australian Water Association

Water

JUNE 2007 57

technical features ,fereed paper

summarises the borefield development progress and Figure 5 indicates the general locations of the borefields over che published geological mapping (GSQ. 2002).

Currencly the project is proposed co consist of seven borefields consisting of a coral of approximately 27 operating production bores yielding a raw water supply in the order of 22 ML/d.

(Artesian) Water Bore Driller's licenses.

The prevalence of artesian conditions also greacly complicated the process of monitoring aquifer piezomecric levels in observation bores during cesc pumping.

Brisbane Aquifer Project Progress Overview Ac che outset, it was envisaged chat approximately 70 investigation holes and 40 production bores would be required co ach ieve the development of a 20 ML/cl raw water source. As it has transpired ch is assessment has been reasonably accurate. To dace approximately 10 km of drilling has been undertaken including 88 invescigacion/monicoring bores and 31 production bores. Borefields have been established at Sunnybank, Runcorn - Eight Mile Plains South , Eight Mile Plains North, Calamvale, Forest Lake and Chandler. A canker station co supply raw water for construction an d ocher uses has been commissioned at Darra. Prospective borefield sites ac Manly, Sunnybank Hills, Larrapinca and Oxley have been subj ect to initial investigation and development has been suspended ac these sites. T able 1

Brisbane Aquifer Project Status Ac the time of preparation of chis paper the Brisbane Aquifer Project is on track co deliver a short-term contingency supply of 20 ML/cl. There will be a need fo r ongoing monitoring and management of the resources and there is potential for longerterm access co these supplies, however arti ficial recharge may need co be undertaken in some of the aquifers co ensure sustainability.

An ongoing hydrological and hydrogeochemical monitoring program for the project is being undertaken co support management and the determination of refi ned aquifer yield estimates.

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Conclusion The Brisbane Aquifer Project is on crack co deliver 20 ML/d for contingency cown water supply. T here will be a need fo r ongoing monitori ng and management of the aquife rs and the potential for artificial recharge can occur after aquifer performance is assessed d uri ng borefield operation.

The key lesson is chat urban groundwater supplies can be implemented and relatively quickly, however closely coordinated multidisciplinary teams are essential.

Because drilling is expensive, careful planning is viral as is down-hole geophysical logging co ensure chat bore construction is optimised. There is also much co be gained in discussions with experienced local water boring contractors, both active and retired.

Finally groundwater is often "where you fin d it". Some previously overlooked and somewhat maligned rock units such as the Neranleigh Fernvale Group have proved to be useful aq uifers.

Acknowledgments T he permission of Brisbane Water co publish chis paper is gratefully acknowledged. The valuable assistance of drilling contractors Henry Vietheer, Ken Dippel, Jon Henderson, Graham H offman and Nevi lle Scells in the collation of drilling data for the planni ng of the Brisbane Aquifer Project is also gracefully acknowledged.

The implementation of chis project could have been achieved without the enormous efforrs of the drilling and test pumping concracco rs, geological support crews, field support teams, the water treatment and reticulation Alliance team and a focussed management team and these efforts are thankfully acknowledged.

Special acknowledgement is made of the invaluable assistance of Wesley Burrows who coordinated the geophysical logging operations fo r the project.

The Authors Peter Evans (peter.evans@envhyd.co m. au) and N Jerome Arunakumaren (jerome@envhyd. com.au) are with EHA Pcy Led, and Andy Moore (ajmcivilptylcd@bigpond.com) is with AJM Civil Pcy Led.

References Geological Survey of Q ueensland, 2002 SouthEast Queensland Region Geoscience Data Set - SEQ GIS Version 2, Ocrober.

58

JUNE 2007

Water

Journal of the Australian Water Association

technical features

MEMBRANE DISTILLATION - A LOW ENERGY DESALTING TECHNIQUE? B Bolto, T Tran, M Hoang Abstract Membrane distillation (MD) is a relatively new process, havi ng been introduced commercially only in rhe lase few years. Ir involves the transport of water vapour through a hydrophobic membrane chat rejects the liquid phase of water, bur vapour can readily permeate the membrane.

Condensation rakes place on the cooler side of the membrane. The driving fo rce is the temperature difference, and hence the vapour pressure difference, between the warm and cool surfaces. Low-grade energy sources can be utilised, the energy requirement being significantly less rhan for thermal distillation. The process in effect combines the advantages of reverse osmosis (RO), b ut has higher yields and che possibi lity of using cheap waste heat energy.

The differential in vapou r pressure of the water is rhe driving fo rce rather than the total pressure. RO is nor adequate for the treatment of high salinity waters and is seen as energy intensive and lacki ng in efficiency as regards the yield of desalted water.

Introduction MD involves the transport of water vapour through a membrane that separates two solutions (Lawson and Lloyd, 1997; EIBourawi et al., 2006) . The general scheme is as shown in Figure I. The process has been explored in various configurations: • direct contact membrane disrillacion (DCMD) has the condensing fl uid in direct contact with the membrane • air gap membrane disti llation (AGMD), where an air gap separates the condensi ng surface from the membrane • sweep gas membrane discillarion (SGMD), which is similar bur utilises air and steam in the gap • vacuum membrane distillation (VMD), which is simi lar to pervaporation bur differs in char the separation is determined by vapour-liquid equilibria rather than selectivity imparted by the membrane.

Solute

tt>mn:ffll

Figure 1. The general principle of MD.

aqueous medium such as wastewater, orange juice or blood. It requires rhe lease equipment and is rhe si mplest to operate.

Fluxes as high as 79 L/m2h have been obtained (Sirkar and Li, 2003) which are competitive with RO, and sale rejections of nearly I 00%, which can nor be achieved with RO at high fluxes (Lawson and Lloyd, 1997). The effects of feed temperature, sale concen tration, feed velocity and partial air pressure on overall DCMD performance have been determined (Schofield et al., I 990a, 19906). Performance on a specific system is highly dependent on rhe membrane used and rhe design of the membrane module. One of the problems with DCMD is rhe relatively low efficiency of heat utilisation, as a large amount of the heat is lost by co nduction through rhe membrane. An answer ro chis is to increase rhe conductive hear transfer resistance by placing an air gap between rhe permeate side of the membrane and the condensing surface.

system is de-aerated. AGMD fluxes are therefore lower than for ocher MD configurations, a recent study using lowgrade thermal energy (hoc side temperatures between 13°C and 75°C) from a salegradient solar pond reporting fl uxes up to 6 L/m 2h (Wal con et al., 2004). The flux was hear transfer limited, and only weakly responsive to vapour pressure gradients between rhe feed and rhe cooling waters.

The method has been applied successfu lly to pure water production and the concentration of various non-volatile solutes. The configuration is the most general and can be used for many applications. Other low-grade hear sources have been suggested, such as thermally stratified waters and ground/air temperature differences.

Sweep Gas Membrane Distillation Ai r or steam stripping with a membrane, as in AGMD, combines the low conductive hear loss of AGMD with the reduced mass transfer resistance of DCMD. Instead of a stagnant layer of air separating the membrane and the condensing surface, air is blown over rhe membrane surface and rhe permeate is condensed in an c:: xrernal condenser. However, the co ndenser muse do a lot more work in this configuration as a ti ny volume of permeate is vaporised in a large volume of sweep gas. Ir has been shown that rhe fl ux is independent of the temperature of the sweep gas. As rhe gas velocity increases to a maximu m, the fl ux increases, bur then stares to decrease because the pressure of the sweep gas also increases so that the resistance in rhe boundary layer increases. There is hence an optimum in the flu x versus gas velocity graph. The approach is especially useful fo r rhe removal of volatile compounds.

Vacuum Membrane Distillation W ith VMD rhe conductive hear loss through rhe membrane is negligible. Ir is most often used to remove volarile

Air Gap Membrane Distillation Direct Contact Membrane Distillation DCMD is best suited co systems where the major component is water, as in desalination or the concentration of an

AGMD substantially reduces the conductive hear loss through the membrane, but in doing chis the mass transfer resistance also increases unless rhe

Increasing mention at membrane conferences of the interesting technique.

Journal of the Australian Water Association

Water

JUNE 2007 59

components from dilute aqueous solutions, but special care muse be taken to prevent membrane wetting, as t.Pinrcrfacc is typically higher than for ocher MD configurations. A fl ux of 70 L/m2h has been obtained with brine at 85°C, higher than for the same cesc module in DCMD mode, which yielded a flux of 54 kg/m 2h (Sirkar and Li, 2003).

The approach is useful for volatile compound removal from aqueous solutions.

With hollow fibre systems having a variety of plasma-polymerised microporous silicone fl uoropolymer coatings, chose wirh the more open coating, more porous membrane wall and larger pore size, lead to greater water vapour permeation (Li and Sirkar, (2005).

Membrane Materials The commercially available membranes chat have been used for MD (Lawson and Lloyd, I 997) include polypropylene (PP), polyvinylidene fluo ride (PVDF), polycecrafluoroechylene (PTFE) and silicone rubber. T he membrane: • muse be porous and have a high permeability • should not be wetted • should not allow capillary condensation to occur inside che pores • muse not alter che vapour-liquid equilibrium of the components in che feed • must have at lease one side in direct contact with the feed water • have a low heat transfer coefficient • should be as chin as possible, to minimise membrane area requirements.

The pore size needs to be small enough co minimise liquid water penetration, yet large enough co give che desired flux. In practice it ranges from 0.02 co l µm, and the membrane is generally 25 co 150 µm chick.

Hollow fibre PP membranes of 200-330 µm internal diameter and wall thickness 50-150 µm have been employed recently (Sirkar and Li, 2003). Ocher workers indicate chat the preferred characteristics fo r a PVDF membrane for VMD are mesoporous structures in a hollow fibre format with pore sizes of 0.05 co 0.2 µm and a high permeability (Cabassud and Wirch, 2003).

60

JUNE 2007

Water

Membrane Fouling DCMD has been observed co give less fou ling than pressure-driven membrane processes in the treatment of waters containing 30 mg/L of soil-derived humic acids, using PVDF and PTFE membranes (Khayec et al., 2004). The membranes showed insignificant fouling at elevated sale concentrations, in contrast with nanofilcracion results, suggesti ng chat membrane distillation is a better process for separating humic acids than pressure driven processes (Khayec and Mengual, 2004).

Experiments with a flat sheet PVDF membrane in DCMD showed a negligible (< 6%) decline in flux with feed waters containing I 160mg/L of NaCl and up co JOO mg/L of soil-derived humic acid (Srisurichan et al., 2005). The presence of calcium reduced che flux considerably when the Ca2 • concentration exceeded the critical coagulation concentration of 0.5-1 rnM. Raisi ng the feed water temperature from 50 co 70°C was also detrimental, increasing the amount of hu mic acid precipitated from 61 co 68%. Performa nce could be easily controlled as che fouling was physical, che loosely packed deposit being easily removed with 0.1 M NaOH, givi ng a 100% fl ux recovery.

Some rather extreme MD experiments using a PP capillary membrane and che sale solution from the processing of animal intestines resulted in severe foul ing of the membrane (Gryta et al., 2001). T he gel layer chat formed on the membrane was composed mainly of protein and NaCl, and could easily be removed with 2 we% citric acid. The problem was avoided by boiling rhe feed, which separated the organic matter as a solid chat co uld be filtered off.

Membrane Wetting There have been some serious problems with membrane wetting causing MD co slow down and, in the worse cases, being brought co a hale (Peng et al., 2005) . The pores of the membrane may become clogged with water even during prolonged use, leading co a decrease in the flux of water vapour (Korin et al., 1996).

Hydrophilic membranes have therefore been explored.

Journal of the Australian Water Association

A membrane has been made from poly(vinyl alcohol) blended with poly(erhylene glycol) and crosslinked with a dialdehyde (Peng et al., 2005). le was investigated as a composite MD membrane by usi ng a PVDF membrane of 0.2 µm pore size as a substrate, precreacing it with an oxidant (potassium dichromace/ sulphuric acid solution) and casting che polymer mixture to produce a membrane having one surface char is hydrophilic. With the hydrophilic layer placed in contact with 3.5% NaCl solution, 9 I% of the fl ux obtained with a hydrophobic membrane was achieved at a separation efficiency above 99% when the temperature of the feed was 70°C. The lower the cooling temperature, which varied from 12-25°C, rhe higher che flux, with a range of 26-23.5 L/m2h. The wetting problem facing traditional MD with che hydrophobic membrane was avoided by using che hydrophilic surface layer.

The reverse type of composite porous hydrophobic/hydrophilic membrane has been proposed, using a polyecherimide as a hydrophilic base polymer to which was added fluorinated surface-modifying macromolecules of MW ~IO kDa (Khayec and Matsuura, 2003; Khayet et al., 2003, 2005a) . The membranes were prepared in one casti ng step, using a phase inversion method with a solution containing che hydrophilic host polymer and che fl uorinated additive. The fluorinated macromolecules migrate co the surface and the fluorine end groups orient themselves cowards the air-polymer interface, reducing rhe surface energy of the hydrophilic base polymer to values close to chat of PTFE. Because only small amounts of the added polymer are required, the bulk properties of the base polymer remain relatively unchanged. The exposed external surface of the membrane was rhus significantly more hydrophobic then che bulk membrane phase. The mean pore size was smaller than char of the unmodified membrane, but there was a lower conductive heat loss through the membrane because of the chick hydrophilic sub-layer chat was filled with water. A comparison of the mechanism of transport through che unmodified

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hyd rophobic membrane and rhe composite hydrophobic/hydrophilic memb rane is schematically represented in Figure 2. The permeate fl ux fo r one product was higher than that of com mercial PTFE membranes, because the composite membranes had a chinner hydrop hobic porous top layer responsible fo r water vapour rransport. T he layer (< 8 µm) was thi nner by an order of magnitude than rhat of co mmercial membranes, resu lting in a lower resisrance to mass transport because of the shorter length of the water vapour transport route. This was despi te the pore size of the composite memb rane bei ng an order of magnitude smaller than that of the commercial membranes. Such a structure could provide an ideal arrangement, with rhe pores being hyd rophilic, facilitati ng condensate draini ng, and rhe membrane surfaces remain ing hydrophobic.

Costs Capi tal costs are difficu lt co esti mate as a large-scale MD plant has yet to be bui lt, bur cap ital and operati ng coses should be significantly less than fo r RO (Walto n et al., 2004). T he process performs best at very low pressures, so chinner pipi ng is employed and fewer problems arise with

leaks and pump failures. Assumi ng the same capi tal cost as sea water RO, the total cost as a fu nctio n of thermal energy cost can be determ ined, and has been found to range from 0.375 to 1.255 US$/ m3 for thermal energy costs of nil to 0.0200 US$/kWh, givi ng an MD/RO cost ratio of 0.50 to 1.67 (Wangnick, 2000) . T hus MD ca n only be co mpetitive when low cost thermal energy is available and/or the sou rce water is too di fficul t for RO treatment. Comparisons for energy costs are 0.025 US$/kWh for natural gas and 0.005-0 .0 15 US$/kWh for large solar ponds. A compariso n ofVM D with RO (T able I ) has shown chat it can compete energetically with RO, bur the fl ux is lower so that a higher membrane area would need to be installed (Cabassud and Wirch, 2003) . More recent estimates pu r the fur ther energy need at l .6 kWh/ m3 when there is energy recovery (Service, 2006).

Memb ranes that are very chi n and are very porous could give a l 00-fold greater permeability, and were shown, in theory, co be co mpetitive at 25°C on energy consump tion and with rhe same level of permeate fl ux . If operated at high temperature and coupled with solar energy, the fl ux could be increased from 5-15 to 40-85 L/m 2 h, reducing the

Capable of processing up to 396 m3/ hr.

Suitable for commercial, industrial, municipal and water treatment applications.

CAST IRON AND STAINLESS STEEL PUMPS

Suitable for commercial, industrial, municipal and wa ter treatment applications.

CARTRIDGE AND BAG FILTERS Capable of withstanding up to 600kPa. Suitable for commercial and water treatment applications.

ELECTRONIC COAGULATION Precipitates and coagulates a wide range of contaminants.

Table 1. Performances of RO and VMD (Cabassud and Wirth, 2003 ).

Suitable for grey water recycling applications.

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technical features

amount of membrane surface needed, and VMD then would clearly be very competitive with RO. With more concentrated salt solutions water fluxes decrease sharply when the co ncentration is above 25% (Yun et al., 2006). Water fl uxes increased as there was an increase in feed temperature and fl ow rare, and when the permeate temperature and salt concentration were decreased. At high salt levels membrane fouling was severe.

Conclusions T he major advantages of MD are (Lawson and Lloyd, 1997; Walton et al., 20 04): • greater simplicity, such as gravity flow through the membrane mo dule • use of very low grade heat, down to 30°C, but typically 60 to 90°C

could give a 100- fo ld faster flux (Cabassud and Wirth, 2003). This would make them competitive at 25°C with RO on energy consumption and with the same level of permeate fl ux. If o perated at h igh temperature and coupled with solar energy, the fl ux could be further increased, so that MD would then clearly be very competitive with RO .

The unknown long-term performance as regards flux and uncertain economic costs have long been emphasised (Lawson and Lloyd, 1997). Flux decay can arise from biofouling, scaling, or the presence of colloidal material in the feed water.

Membrane wetting is another hurdle that can be overcome though by a hydrophobic composite membrane that has an appropriate hydroph ilic surface.

The Authors

• the ability to treat highly concentrated wastes, e.g. reject brine from RO

Dr Brian Bolto, Dr Thuy Tran and Dr Manh Hoang (emails:

• low operating pressures, from zero to a few h undred kPa

brian.bolto@csiro.au; th uy.tran@csiro.au; manh.hoang@csiro.au) work for CS IRO Man ufactu ring and Materials T echnology, C layton, Victoria.

• better p rocess safety • feed water does not req uire extensive pretreatment • reduced chemical interaction between the membrane and feed components • less demanding memb rane mechanical pro perties • complete or very high rejection of salt, colloids, cells and o ther impurities.

The process is claimed to be cost compet itive in several areas: • isolated locations using solar energy (Bier and Plantikow, 1995; Banat et al., 2002; UNESC O C entre fo r Membrane Science and Technology, 2006 ) • waste heat applications, as from electrical generation power plants • geo thermal waters • mobile military applications • treatment of R O concentrate.

Its disadvantages are (El-Bou rawi et al., 20 06): • relatively low permeate fl ux co mpared to RO • flux decay arising from co ncentration and temperature polarisation • membrane and module design for MD • high thermal energy consumptio n • uncertain energy and economic costs foe each MD mode.

Because the fl ux is lower than that fo r RO a higher membrane area is required.

Modelling has shown that M D membranes that are very thin and are very porous

62 JUNE 2007

water

References Banat, F., Jumah, R. and Garaibeh, M. (2002).

Exploitation of solar energy collected by solar stills for desalination by membrane d istillation. Renewable Energy 25, 293-305.

Bier, C. and Plancikow, U . (1995). Solarpowered desalination by membrane distillation. Proc. IDA World Congress, Abu Dhabi.

Cabassud, C. and Wirth, D. (2003). Membrane distillation for water desalination: how to choose an appropriate membrane.

Desalination 157, 307-314.

El-Bourawi, M. S., Ding, Z., Ma, R. and Khayet, M. (2006). A framework for better understanding membrane distillation process.]. Membrane Sci. 285, 4-29.

Gryta, M ., Tomaszewska, M., G rzechulska, J. and Morawski, A. W. (200 1). Membrane distillation of NaCl solution containing natural organic matter. J. Membrane Sci. 181, 279-287.

Khayet, M. and Marsuura, T. (2003).

Application of surface modifying macromolecules for the preparation of membranes for membrane distillat ion .

Desalination 158, 51-56.

Khayet, M., Velazquez, A. and Mengual, J. I. (2004). D irect contact membrane distillarion of humic acid solut ions. J. Membrane Sci. 240, 123- 128.

Khayet, M., Suk, D . E. , Narbaitz, J. P., Santerre, J. P. and Matsuura, T . (2003).

Study on surface modification by surface mod ifying macromolecules and its applications in membrane separation processes. J. Appl. Polym. Sci. 89, 290229 16.

Khayet, M. and Mengual, J. I. (2004). Effect of salt concentrat ion during the treatment of

Journal of the Australian Water Association

humic acid solutions by membrane distillation. Desalination 168, 373-381.

Khayet, M., Mengual, J. I. and Matsuura, T. (2005a). Porous hydrophobic/hydrophilic composite membranes: Application in desalination using direct contact membrane distillation. J. Membrane Sci. 252, 101-113.

Khayet, M., Matsuura, T . and Mengual, J. I. (20056). Porous hydrophobic/hydrophilic composite membranes: Estimation of the hydrophobic layer thickness. J. Membrane Sci. 266, 68-79.

Korin, E., Ladizhensky, I. and Korngold, E. (1996). H ydrophilic hollow fibre membranes for water desalination by the pervaporation method. Chem. Eng. Proc. 35, 451-457.

Lawson, K. W. and Lloyd, D. R. (1997).

Membrane dist illation. J. M embrane Sci. 124, 1-25.

Li, B. and Sirkar, K. K. (2005). Novel membrane and device for vacuum membrane distillation-based desalinat ion process.]. Membrane Sci. 257, 60-75.

Peng, P., Fane, A. G. and Xiaodong, L. (2005).

Desalination by memb rane distillation adopting a hydrophilic membrane.

Desalination 173, 45-54.

Service, R. F. (2006). Desalination freshens up.

Science 313(5790), 1088- 1090.

Schofield, R. W., Fane, A. G., Fell, C. J . D. and Macoun, R. (1990a). Factors affecting flux in membrane dist illat ion. Desalination 77, 279-294.

Schofield, R. W., Fane, A.G., and Fell, C. J. D .

(19906). Gas and vapour transport through microporous membranes. II. Membrane distillation. J. Membrane Sci. 53, 173-185 .

Sirkar, K. K. and Li, B. (2003). Novel membrane and device for direct contact membrane distillat ion-based desalination process: Phase II. Desalination and Water

Purification Research and Development Program Final Report No. 96, US Department of the Interior, Bureau of Reclamation, Denver.

Srisurichan, S., Jiraratananon, R. and Fane, A. G . (2005). Humic acid foul ing in t he membrane distillation process. Desalination 174, 63-72.

UNESCO Centre for Membrane Science and Tech nology (2006). Membrane process applicat ions. http://www.membrane.unsw.edu.au/ research/mpa.htm Walton, J. , Lu, H., Turner, C., Solis, S. and Hein, H. (2004). Solar and waste heat desalination by membrane distillation.

Desalination and Water Purification Research and Development Program Report No. 81, US Department of the Interior, Bureau of Reclamation, Denver. \Xfangnick, K. (2000). Present status of thermal regeneration desalination techniques.

Desalination and Water Reuse Quarterly 10(1 ), 14-21.

Yun, Y., Ma, R., Zhang, W. Fane, A. G. and Li, J. (2006). Direct contact membrane d istillatio n mechanism for high concentration NaCl solutions. Desalination 188, 25 1-262.

tprhnical features

water supply

fereed paper

UV SPECTROMETRY IN DRINKING WATER QUALITY MANAGEMENT C Chow, R Dexter, L Sutherland-Stacey, F Fitzgerald, R Fabris, M Drikas, M Holmes, U Kaeding Abstract

This paper provides a brief overview of current applications of UV/Vis spectrometry in the drinking water industry and particularly the use of UV absorbance as a surrogate measure for dissolved organic carbon (DOC) concentration, chlorine demand and disinfection by-product (DBP) forma tion, such as trihalomethanes (THMs) Mul tiple wavelength spectrophoto metry is compared with the conventional single wavelength (UV254) approach.

Field trials of the S::CAN Spectro::lyser™ (submersible UV /Vis mul tiple wavelength spectrometer) at the Myponga WTP in South Australia to evaluate the on-line capabi lity for real rime chlorine demand prediction are discussed.

Introduction

Natural organic matter (NOM) is an important co nsideration in drinking water quality management. NO M is a complex matrix of hererogenous organic material which co mes from decaying terrestrial and aquatic organisms.

A number of characterisation techniques have been developed to enable a better understanding of the impact of organic compou nds on treatment processes. NOM is more commonly represented by the measurement of total (T OC) or dissolved organic carbon (DOC) concentration due ro the high cost and complexity in quantifying separate compone nts.

Generally, T OC and DOC are determined usi ng an organic carbon analyser. Simple analytical techniques, such as single wavelength UV abso rbance measurements (UY254) or colour (456 nm) can be used as surrogate parameters to monitor the co ncentration of NOM and they are widely applied by water treatment plant (WTP) operators as parameters to assess treatment plant performance.

The Australian Drinking Water Gu ideli nes (ADWG) reco mmends rhac a hazard analysis and critical control point (HACCP) approach be used as an early warning of process upset or deterioration in water quality. This can be achieved by using strategically located, continuous on-

line monitors linked to a supervisory control and data acquisition (SCADA) system. Conti nuous on-li ne UV absorbance monitoring can be used at a number of critical control points including at raw water intake, of clarified water and at prechlorinacion. Further mon itoring can be done at pose-chlorination sites and in the distribution system to feedback to the control sites. This mo nitoring technology has the potential to assess water quality as well as treatment process performance including coagulation and chlorination.

Measurement of single wavelength UV absorbance is one of rhe simplest methods of assessi ng water quality and a range of spectrophotometers including both laboratory and handheld versions are widely available. In contrast to single wavelength devices, the full range UV/Vis absorbance measuring instruments can be used to obtain more accurate and diverse data from which ocher water quality parameters such as DOC concentration can be determined, fo llowing sui table con version ch rough established relationships. The use of differential spectrometry to detect compositional changes and alarm at levels is another benefit of using full spectral devices which would nor be possible for single frequency devices or even calculated standard parameters. The recen c developments in instrument portability have resu lted in a number of rel iable online/in situ monitoring instruments which are now commercially available. Together with the development of chemometric approaches, a number of quantitative analysis techniques, such as principal component regression (PCR) and partial lease-squares (PLS), have been implemented as part of the instrumentation software to improve che reliability of the measurement.

T his paper provides an overview of current applications of UV /Vis spectrometry in the drinking water industry and particularly che use of UV absorbance as a surrogate measure for dissolve organic carbon (DOC) concentration, chlorine demand and disinfection by-product (DBP) formation, such as crihalomechanes (T HMs). Special reference will be made to comparing the use of multiple wavelength quantification with the conventional single wavelength (UV254) approach.

In addition, the field trial results of the S: :CAN Speccro:: lyser™ submersible UV/Vis multiple wavelength spectrometer at the Myponga WTP in South Australia co evaluate the on-line capability for real time chlorine demand pred iction is discussed.

Experimental and Instrumentation

Co nventional labo ratory methods for UV/Vis measurements require a sample to be manually placed in the spectrophotometer using a quartz cuvette.

UV or visible light at a certain wavelength, or range of wavelengths, is transmitted thro ugh the sample. T he spectrophotometer measures how much of the light is absorbed by the sample. There are several types of laboratory UV/Vis spectrophoto meters available, such as si ngle bea m and double beam design, with the use of different types bei ng dependent upon the application.

The S::CAN Speccro::lyser™ hardware (Langergraber et al. 2002), developed in Austria, was supplied by DCM Process Control Led, NZ. Ir is different in chat rather than bringi ng che sample to the unit, the unit is submersible and can go directly into the water. l e co mprises a robust bur sensitive double beam UV /Vis-spectrometer (200 nm to 750nm) with optical pathlength in a selectable range of 0.05 to I 0 cm. The instrument was designed based upon the principle of the phorodiode array (PDA) spectrophoto meter, which has no moving pares and has the advantage of reagent free operation. Full spectrum UV/Vis absorbance measurement provides concenrracion data for a number of parameters and calculated equivalents fo r ochers (such as TOC, DOC, nitrate, nitri te, rurbidicy, total suspended solids and parricle size) . l e has proved to be a useful warni ng tool of any sudden charges of water quality. Co nsequently the S::CAN Spectro: :lyser™ has many diverse

A multiwavelength in-line spectrophotometer can be a helpful tool for real-time monitoring.

Journal of the Australian Water Association

Water

JUNE 2007 63

technical features

applications, including monitoring of drinking water, domestic and industrial waste waters.

Water samples were chosen from seven major water authorities around Australia to represent the wide variation in water quality included both surface and ground waters. A laboratory trial was conducted using standard laboratory procedures for UV254, colour, DOC and rrihalomerhane fo rmation potential (THMfp) measurements (Bennett and Drikas, 1993; APHA et al., 1998).

As per rhe standard methods, sample filtration th rough 0.45 micron fil ter was performed. The comparison focussed on using the S::CAN Spectro::lyser™ in rhe on-l ine/in situ application without prior sample fil tration, as would be rhe case in real-rime monitoring.

forward prediction of coagulant dose (van Leeuwen et al. 2005).

T his technique only requires very simple instrumentation and can be performed by the operators at the treatment plant.

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However, care must be taken when using UV254 as a DOC surrogate, particularly when it is to be used fo r control purposes. Under these conditions, rhe apparent correlations of DOC to UV25 4 must be verified at times of compositional variances.

Good correlations usually occur only in compositionally stable waters. Figure 1 indicates that raw water has higher UV absorbance (UV 254) per unit DOC than treated water. Good prediction can only be obtained from well characterised waters.

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The use of multiple wavelength measurement together with PLS for quantitative calibration is well documented in the literature (Haaland and Thomas, 1988; Thomas and Gallor, 1990, Langergraber et al., 2003).

The analytical results (Figure 2) obtained from standard laboratory methods and rhe S::CAN Specrro::lyser™ co rrelated very well (UV2;f R2 = 0.98; Colour: R2 = 0.96; DOC: R2 = 0.84).

Figure 1. Correlation between DOC and UV 254 for both raw and treated waters.

A two week field trial using the S::CAN Specrro::lyser™ was conducted at the Myponga WTP. The S::CAN Spectro::lyser™ was installed at the filtered water tap (prior to chlorination) at the WTP laboratory. A chlorine demand prediction algorithm based on previous laboratory data was used to determine the real rime chlorine demand of the filtered water. During the two week field trial, 19 grab samples were taken for laboratory chlorine demand measurement. In addition, field chlorine residuals from the routine sampling program at a downstream location (Almond G rove Road - location number 1607) were used to evaluate the concept of "chlorine demand sensor" as a real rime control of chlorine dosing. In terms of

practicality, chlorine demand can also be estimated based on the difference between the chlorine set-point at rhe WTP and the residual at the downstream locations provided rhe water travel time is known.

Results and Discussion UVabs as a surrogate measurement of DOC - the advantages of using multi-wavelength measurement UV 254 has been identified as a useful surrogate measure for DOC although it predominantly represents only rhe aromatic NOM character. UV25 4 is becoming a popular parameter for water treatment operators to assess treatment performance and also as one of the parameters for feed

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Ir should be noted rhar very fine particulates(< 0.45 micro n filter) can contribute to the UV25 4 and colour readings of a water sample obtained using standard optical laboratory instruments.

S::CAN has a mathematical fu nction to compensate for particle related optical effects giving it a distinct advantage over conventional optical devices when used for

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Figure 2. Compari son of analytical results between laboratory standard procedures and S::CAN Spectro:: lyser™ (a) UV254, (b) colou r and (c) DOC. Sample filtration was included in the laboratory standard methods whi le S::CAN Spectro::lyser™ measurement was performed without fi ltration .

64

JUNE 2007

Water

Journal of the Australian Water Association

technical features

app lications when fine particulates are p resent, such as in waters of che lower River Murray. T he advantage of using mu ltiple wavelength measurements PLS calibration (S::CAN) can be seen in Figure 2c, where che p redicted D OC values closely march chose of actual values fo r both raw and treated waters.

Prediction of chlorine demand Conventional meth ods used to determ ine b ulk water chlorine demand an d residual ki netics are contact time dependent and often require several days to comp lete in order to match these to che actual water retentio n rimes in distribution systems.

Water supplies, having variable water quali ry, may have a variable ch lorine demand . T his requi res substantial changes to be made to che app lied d isin fecta nt dose if d isinfectio n res iduals are to be maintained within required ranges th ro ugh out the distribu tion system. This presents a challenge to operators when attem pting to control secondary disinfection as feed back loops are usually of the order of several days, making che p rocess highly react ive.

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2004/11/09 2004/11/13 2004/11/17 2004/11/21 2004/11/25 Figure 3. Comparison of rea l time chorine demand monito ring using o n-line UV absorba nce measurement and ch lorine demand determined in a laborato ry usi ng conventi onal method . Pink line: on-line chlorine dema nd predi ction by S: :CAN Spectro ::lyser™. o : Laboratory chlo rine dema nd measurement from grab samples. + : Determined ch lorine deman d based on chlorine residual at a locatio n (A lmond G rove Road - location number 1607) down stream from the M yponga WTP w ith travel time correcti on.

Based on a 24-monch laboratory study using water samp les rangin g in water quaJiry, UV absorbance measurement was identified as che best surrogate parameter fo r rapid ch lorine demand assess men t. A linear relationsh ip was determ ined betwee n chlorin e demand and UV 254 absorbance from which p redict io n can be made with an accuracy of better than ± l mg/L chlorine d emand (Fitzgerald et al., 2006).

A particularly useful featu re of the S::CAN Speccro:: lyser™ is the on-line/in situ mon itoring capabil ity. During the 2-week on-line monitoring t rial conducted at the Myponga WTP, the S: :CAN Speccro:: lyser™ performed well, with incorporation of specifica lly developed software. On-line chlori ne demand prediction based o n UV absorbance measurement was able to be displayed in real time o n che instru ment (Figure 3) . T he chlorine demand p redictions marched well with th e laboratory measu rements made of grab samples collected d u ring che period.

Note th at grab samp ling did not occu r during events of major changes in chlorine demand as detected by che S::CAN Speccro::lyser™ caused by plane shutdowns . This indicates chat a samp ling p rogram can be refined using a S::CAN Speccro: :lyser™ to enable sam ples to be taken when water quality changes or events occur rather than on a time, flow or random basis.

Furthermore, the "chlorine demand sensor" concept was studied usi ng chlorine residual

Journal of the Australian Water Association

water

JU NE 2007 65

technical features

B .... ' '. '.

water supply measurement at a location (Almond Grove Road) downstream of rhe WTP. 600 The feasibility of using UV absorbance 0 500 measurement (prior to chlorination) to ,-... estimate chlorine demand of the water as 0 0 ~ 400 a way to control chlorine dosing and ;:::l ..__, manage residual in rhe distribution c9- 300 system was assessed. The chlorine demand (field data) shown in Figure 3 200 E-< was estimated based on rhe difference 100 between rhe chlorine sec-point at the WTP and chlorine residual at rhe 0 Almond Grove Road sampling point 0.6 0.2 0.4 0 after travel rime co rrection (travel rime is approximately 2 days), rhe results also marched well with the real time chlorine demand measurements using the Figure 4. Relationship between UV254 and S:: CAN Spectro::lyser™. Although chis THMfp from water samples collected for a study didn't provide a fu ll range of water q uality. demonstration of usi ng on-line UV spectrophotometer fo r chlorine dosing chat is convenient and technically easily control, the results obtained so far indicate achievable. Using single wavelength feasibility of the concept. More case studies (254nm) measuremen t as a surrogate for are required to confirm the practicality of these parameters can only provide limited chis control co ncept. A new project in rhe accuracy of prediction and care must be CRC for Water Quality and Treatment is caken co ensure reliable measurement. The currently underway co evaluate the S::CAN use of a multiple wavelength instrument Speccro::lyser™ in a range of drinking with PLS calibration such as S::CAN water related projects.

Specrro::lyser™, can improve the accuracy Prediction of THM formation potential and reliability of measurement. In addition , In a similar way co DOC and chlorine the optio n of using ir in an on- line/in situ mode provides an extra dimension and demand, a generally linear relationship (R2 = 0.92) was found between UV 25 4 and makes it a potentially helpful tool in managing water treatment operation and THM formation, based on laboratory distribution system performance through analyses of grab samples (Figure 4) . A more automated control. is a useful cool that can derailed comparison between laboratory be used on-line at a critical control point determined and S::CAN Specrro: :lyser™ prior to d isinfection as part of a HACCP determined THMfp results can be found in process to provide early warning of process Mosse (200 3). upset/water quality deterioration.

T he capability for operators co use simple cools such as single wavelength or fu ll Acknowledgement UV/Vis spectrum measurements to predict The authors thank Power and Water THM formation offers a number of Authority, N T ; Gippsland W ater, Vic; advantages when managing distribution South Australian Water Corporation; Gold system performance. As previously discussed , care should be taken when using UV 254 (single wavelength) only for prediction and measurement using a full spectrum (multiple wavelength) d etection instrument such as S::CAN Spectro: :lyser™ is recommended in order to lower the risk of significant errors. Regular cross checking To reach the decision-makers in of S::CAN Spectro::lyser™ output with the water field, you should actual laboratory analysis both during stable consider advertising in Water water conditions and during times of water Journal, the official journal of quality changes is required in order to Australian Water Association. validate the acquired on-line data.

~

Water Advertising

Conclusion For water utilities required to manage a dynamic water distribution system, the application of UV absorbance meas urement enables rapid assessment of water quality

66 JUNE 2007 Water

For information on advertising rates, please contact Brian Rault at Hallmark Editions, Tel (03) 8534 5000 or email brian.rault@halledit.com.au

Journal of the Australian Water Association

Coast Water; Melbourne Water; Sydney Water; and the Water Co rporation,WA, for the coordination of the water sampling programme, and DCM Process Control Ltd for supply of the S:CAN Spectro::lyser™ .

The Authors Christopher Chow (email Chris. Chow@sawater.com .au),

Fiona Fitzgerald, Rolando Fabris, Mary Drikas, are wirh the Co-operat ive Research Centre for Water Quality and Treatment, Australian Water Quality Centre. Rob Dexter, Luke SutherlandStacey are wirh DCM Process Control Ltd, Auckland , New Zealand (Rob@DCMprocesscontrol.com).

Mike Holmes and Uwe Kaeding are with United Water International.

References APHA, AWWA and WEF 1998 Standard

Methods For The Examination of Water and Waste Water, 20th Edition, American Public H ealth Association , Washington, DC. Bennett L. E. and Drikas M. (1993) The evaluation of colour in natural waters. Wat. Res. 27(7), 1209-1218.

Fitzgerald F., Chow C.W.K. and Holmes M .

(2006) Disinfectant demand predict ion using surrogate parameters - A tool to improve disinfection control. j Water SRT - Aqua 55 (6) 391-400.

Haaland D.M. and Thomas E. V. ( 1988) Partial least-squares methods for spectral analyses. 1. relation to other quancitative calibration methods and che extraction of quanricacive information. Anal Chem 60, 1193- 1202.

Lagergraber G , Fleisch mann N and Hofstadter F. (2003) A multivariate calibration procedures for UV/VIS spectrometric quantification of organic maccer and nitrate in wastewater. Water Science and Technology 47(2) 63-71.

Langergraber G., Fleischmann N. and Hofscaedcer F (2002) A multivariate calibration procedure for UV/VIS spectrometric quantification of organic matter and nitrate in wastewater,

Fleischmann N. et al. (Eds.): Proceedings of the International /WA Conference on Automation in Water Quality Monitoring AutMoNet 2002, May 21-22, 2002, University of Agricultural Sciences Vienna (BOKU); Vienna, Austria, pp. 233-240.

Mass e P. (2003) The Measurement of water

quality parameters using the S::CAN Spectro::lyser™. Internal Report, DCM Process Control.

Thomas 0. and Galloc S. (1990) Ulcraviolec mulriwavelengch absorptiomecry (UVMA), for che examination of narural waters and wastewaters Pare I: General considerations.

Fresenius] Anal Chem 338, 234-237. van Leeuwen J., Daly R. and Holmes M. (2005) Modeling the treatment of drinking water to maximize d issolved organic matter removal and minimize disinfection by-produce fo rmation. Desalination 177, 81 -89.

technical features II.

lfereed paper

STRATEGIC WATER QUALITY MONITORING FOR DRINKING WATER SAFETY S Rizak, S E Hrudey Abstract D rinki ng water quality managemenc and treatment muse assure the safety of drinki ng water for pub lic health protection. A water supplier wishing to maximise its ability to detect contaminated drinking water and provide greater public health protection must ensure that adequate resources are dedicated to a strategic, system-specific and evidence-based monitoring system wh ich effectively informs about risk. This requires collecting data char increase understanding of the encire water supp ly system and provide improved insight on hazards, treatment performance and the overall vul nerability of rhe system.

Introduction

Ulrimarely, assuring drinking water safety requires a commitment to a comprehensive approach to risk management. This implies rhe need to develop an effective strategy char is preven rive rather chan reactive and char aims to:

• implement effective measures to manage che risks from those hazards; and • invest resources appropriately to maximise rhe outcomes char are intended.

Understanding che water supply system, che hazards char can compromise drinking water quality and safety, rhe performance of treatment barriers, and the integrity of the distribution system requires an effective monitoring strategy. T he potentials and capabilities of a monitoring system are directly related to, and ofren inseparable from, rhe potentials and capabilities of managi ng rhe system and irs risks.

While intuition may suggest rhar most of our monitoring resources be devoted to checking treated drinking water qual ity (verification or compliance monitoring), chis is nor adequate to guarantee safety. T he inherent limitations in this type of monitoring and rhe difficulties arising in interpretation of results makes ir an

'What, where and when to monitor.

• promote understanding of the encire water supply system and che hazards rhar are present;

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ineffective strategy by itself (Rizak and Hrudey 2007a). A water supp lier wishing to maximise its ability to derecr co nraminared drinking water and provide greater public health protection must ensure rhar adequate resources are dedicated to a strategic, system-specific and evidence-based mo nitoring system which effectively informs about risk. This requires collecting data char increase understanding of the entire water supply system and provide improved insight on hazards, rrearmenc performance and the overall vulnerability of rhe system.

The following is a summary of a recent report of rhe CRC for Water Quality and Treatment entitled, Developing Strategic

Water Quality Monitoring Systems for Drinking Water Safety (Rizak and Hrudey 20076). Derived from an analysis of a number of waterborne disease outbreaks, and supplemented with case studies, important principles and elemenrs of a strategic water quality monitoring system are described. The complete system is illustrated in Figure 1.

JUDGE T REAT ED DRI NKING WATE R QUA LITY

(normal. events. compliance)

\

Ea rly Warning System

• e,,-ents trigger enhanced monitoring

Operational Monitoring

Verification Monitoring

Consumer Satisfaction Monitoring

Figure 1. Strategic water quality mon itoring system for drinking water safety.

Journal of the Australian Water Association

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JUNE 2007 67

technical features 18)

water supply Where to Monitor

Box 1. Treatment Preventio n and Outbreak Prevention.

Source water monitoring

Source water monitoring is che foundation of strategic, evidence-based monitoring as ic provides important info rmation chat enables a water supplier co understand ics catchment, what hazards arise and the contamination challenge they present.

Understanding source water characteristics under a variety of conditions and the level of risk is also essential for ascertaining what level of treatment is appropriate and what improvements may be necessary.

Poor knowledge of the water source and inadequate treatment are typical underlying causes of many waterborne disease outbreaks that have occurred (Hrudey and Hrudey 2004).

Source water monitoring is preventive rather than reactive in that it is earlier in the process and may provide an oppormnity fo r real-time process control (S curdevanc Rees et al 2006, Gullick et al 2003, WHO 2004a}.

Treatment performance/operational monitoring

Diligent operational monitoring of processes and treatment performance is also essential. Because of the lack of realtime measurements of all possible contaminants in water, che advantage of monitoring treatment performance is chat effective operational surrogates can be mo nitored continuously in real-time and potentially identify incidents as they occur.

If water treatment is well understood under a variety of conditions and performance is monitored continuously, then greater confidence in water safety can be assured.

Treatment performance monitoring is the key co identifying ineffective treannent processes such as inadequate disinfection, shortening of fil ter runs and degraded filte red water quality. Deficiencies such as inadequate process control monitoring, not paying attention co changes in process control monitoring (boch gradual and sudden), or not recognising or understanding the significance of process mo ni toring are important risk factors of many waterborne outb reaks (H rudey and Hrudey 2004) . There have been many instances where the significance of treatment performance data is nor understood nor used effectively, missing a valuable opportunity for early recognition of water quality deterioration and potentially preventing or reducing che scope of an outbreak.

Box l provides two recent examples of waterborne disease outbreaks in Canada 68 JUNE 2007

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In the case of Walkerton, Canada in 2000, where manure contamination overwhelmed the fixed chlorine dose, hod the treatment requirements of a chlorine residual of 0.5 mg/Lfor 15 minutes contact time been mai ntained , this would hove been adequate to inactivate the pathogens E. coli 0157: H7 and Compylobac/er spp responsible for 7 deaths and over 2300 illnesses. The monitoring requirements for the Walkerton water system were doily measurement of chlorine residual and the monthly routine sampling of row water and the distribution system for microbiological hazards. However, chlorine residuals were not measured for several days around the contam ination period. Hod mon itoring been conducted as required, the operators should hove been able to detect the problem at least within 24 hours of the contamination, shut the contaminated well down, and reduce the scope of the outbreak (Hrudey and Walker 2005).

Furthermore, hod continuous chlorine residual monitors with on automatic shutoff been implemented, a measure costing only approximately $8000, the outbreak could hove been prevented entirely (O'Connor 2002 pp 14-15).

Similarly in North Bottleford, Canada in 200 1, poor treatment performance was observed for a prolonged period ofter maintenance was carried out on the solids contact unit (SCU). When the SCU wos brought bock online, minimal clarification was being achieved in the SCU due to difficulties in re-establishing on effective floe blanket. This, along with unoptimi sed filtration, resulted in treated water turbidities being much higher than usual. Given the poor treatment performance ond the known vulnerability of the river water source to contamination by Cryplosporidium parvum, the operators should hove recognised the serious risk presented. Although regulatory req uirements were not exceeded, had normal ranges of turbidity and the implications of poor turbidity removal been understood, appropriate actions could have been token to inform public health officials. As it was, this poor performance continued for several weeks and a breakthrough of C. parvum occurred ultimately affecting between 5800 and 7100 people (Laing 2002). where attention had not been given co indications that processes were operating out of normal range. In these and other cases, had greater attention and awareness been placed on understanding processes and treatment performance, effective responses could have been initiated to prevent or reduce the scope of the outbreaks.

Monitoring in the distribution system

Distribution system contamination is a significant problem and is a major cause of waterborne disease outbreaks (Craun and Calderon 2001). The problem of having a

good quality water supply and then fai ling co protect it in the storage and distribution system is a recurring theme co many of these outbreaks including two fatal episodes in Missouri, USA (Box 2).

Because treated drinking water quality monitoring is limited in its ability co provide the real-time operational information necessary for preventing potential contamination from reaching consumers, monitoring systems must also include additional strategies co help detect changes withi n the distribution system and potential contamination more effectively.

Developing and utilising operational

Box 2. Fatal Outbrea ks Caused by Distribution System Contamination.

In January 1990, Cabool, Missouri, USA, a town of approximately 2,100 people, experienced on outbreak of E.coli 0157:H7 causing at least 243 cases of gastrointestinal disease with four people dying (Swerdlow et al 1992). Drinking water for Cabool was a high quality, untreated groundwater supply with largely protected well-heads. Monitoring data for this supply showed that no coliforms had ever been detected in any source water sample. The distribution system however was in poor repair and vulnerable to sewage contam ination at several locations. Records showed that 35% of the total flow was lost, signalling that ma ins were leaking, meters were inaccurate, or that there was unrecognised, unmetered use. The sewer system was also in poor condition and frequently caused sewage back-ups and overflows. The outbreak occurred after replacement of 45 in-ground water meters and two major water main repairs following extreme cold weather temperatures. There was visual evidence of several sewage overflows, which happened regularly in this system, and the most plausible explanation for the outbreak appeared to be direct crosscontamination (Geldreich et al 1992).

A November 1993 outbreak of solmonellosis in Gideon, Missouri USA was attributed to contaminated storage facilities. More than 650 people of the town's 1,100 were estimated to be affected and 7 deaths occurred (Clark et al 1996, Angulo et al 1997). The Gideon water system was sourced from high quality groundwater from two deep (396 m) bores and the water was distributed without disinfection or treatment. The distribution system was in poor condition and large pressure drops were noted during high flow or flushing conditions, indicating problems with system integrity. The system had two municipal storage tanks, one that was connected to a private water storage tonk. Evidence suggested that bird faeces hod conta minated the municipal water storage tonk. The outbreak was believed to hove been triggered when extreme low temperatures caused o thermally-induced turnover in the storage tank thot mixed contaminated water into the water being distributed to the community (Clark et al 1996, Angulo et al 1997).

Journal of the Australian Water Association

technical features

parameters such as turbidity (or particle counts), chlorine residual, pH, pressure, can provide more timely information of changes from normal and better coverage of the distribution system. Monitoring pressure transients is also suggested to id entify and reduce hydraulic conditions char m ight allow water to become contaminated by intrusion (LeChevallier et al 2003).

Furthermore, placing more attention and resources on preventing contamination in the distribution system is imperative for reduci n g the risk of waterborne d isease outb reaks (Craun and Calderon 2001 ).

Cross-connection control programs and approved backflow prevention devices are important p reventive measures. Ocher important m easures should includ e maintaining adequate pressu re and ch lorine residual throughout the system, adequate d isinfection and monitoring after repairs, leak detection programs and replacing aged pipes, covering and protecting storage facilities and inspecti ng chem regularly to ensure small animals and birds cannot gain entry, as well as increasing corrosion control efforts (NHMRC 2004 , Craun and Calderon 200 1, Kramer et al 1996).

When to Monitor Reviews of historical drinking water outbreaks indicate that outbreaks are almost invariably li nked to som e significant change in conditions, environmental or other, char provides a sudd en challenge to a water system.

Therefore, in addition to monitoring the source water, treatment performance and distribution system to understand the water system under normal conditions, a strategic, evidence-based monitoring system should also incorporate collecting in fo rmation on events, whether seasonal or sporadic, to understand what influence

Box 3. Early Detection of Contam ination.

In November 2004, o major contam ination incident affecting the water supply ot Leongatha, Victoria, a town of about 5,000 people, was detected after a dramatic increase in raw water turbidity, and an associated rapid loss of chlorine residual following treatment, was noticed by operators. Initial investigation at the final storage reservoir revealed a noticeable odour and further investigation located the source of contamination to be a burst pipe carrying supernotant from a doiry shed effluent. Approximately 200,000-300,000L of contaminated water was discharged to the 17 M L reservoir.

This early detection allowed immediate actions to be instigated to protect public health and restore water quality. The Leongatha water supply system hos three treated water storages . Initial actions were to stop the plant and flush the affected reservoir until the treated storage dropped to the level that required the plant to restart. When the plant restarted, treated water turbidity was high and there was di fficulty in maintaini ng a chlorine residual so slug dosing of the treated storages was carried out. Microbiological resul ts indicated no f . coli were detected in the treated water or distribution system but viable Cryptosporidium and Giardia were identified in the reservoir and non-viable Cryptosporidium and Giardia were identified in the treated water.

A boi l water alert was issued to warn the public and alternate water supplies were provided to necessary locations before the contamination reached the town system. By the following day, turbidity readings were back to normal and a constant chlorine residual was achieved . Once treated water storage was filled with good quality water, flush ing of the system commenced (Ashworth 2005).

unusual weather and other environmental and operating condit ions have o n source water quality and treatment. Ir is these periods of change from normal steady state operation when the system is most challenged that can provide the most useful in formation on a water sup ply and its vu lnerabilities.

Essentially, any sudden or extreme change in water quality, flow or environmental conditions (extreme weather, rainfall , flooding) , treatment variations, maintenance and repairs, power o utages, should heighten awareness of po tential problems and should trigger increased monitoring throughout che water system.

Even t monitoring also enab les the d evelopment o f early warning systems to promptly identify potential changes to water quality, and thus provid e the opportunity for real-rime process control (Sturdevant Rees et al 2006 , Rizak and Hrudey 20076). Box 3 illustrates a case where early detection of contamination

and effective incident response prevented a potential outbreak.

What to Monitor

Microbial versus chemical Waterborne m icrobial pathogens re present the clearest and m ost acute risk to drinki ng water safety (NHMRC 2004, Hrudey and Hrudey 2004) . Chemical contami nation does occur and has been documented to cause serio us heal ch outcomes via drinking water in some specific cases. However, unl ike the pervasive threat from microbial pathogens, waterborne outbreaks caused by chemicals typically arise from specific natural local conditions or from sitesp ecific human contamination (d istribut ion cross-connections, inadvertent ch emical addition , sabo tage).

Of the some 200 chemical co ntaminants listed in drinking water, only a limited number has established evidence of causing human health impacts via drinking water consumption. These priority contaminants

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Journal of the Australian Water Association

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JUNE 2007

69

technical features

include arsenic, fluoride (in excess of concentrations used for dental protection) and selenium, arising primarily from natural contamination, nitrate arisi ng fro m both natural and agricultural practices, and lead arising primarily from the use of lead in p lumbing. Iron and manganese are also mentioned as frequent sources of aesthet ic water quality problems that may lead consumers to use other water supplies that may be unsafe regarding pathogens (WHO 20046) .

Chemicals used in water treatment may also pose a significant risk because of the potential for inadvertent contamination episodes. Most ocher chemicals are only likely to be an important risk in specific local circu mstances. Hence, these risks do not warrant the same level of pervasive attention as the microbial pathogens or the priority chemicals unless there is some specific evidence or reasonable inference chat they pose an important local problem.

Disinfection by-pro ducts and the concern with possible adverse healch effects sho uld also be monitored bur this issue should never compromise assu ring effective management o f pathogens, wh ich are fou nd everywhere. The health impacts from chronic low-level exposure to ch emicals via drinking water are tenuo us com pared to the certainty of waterborne d isease caused by m icrobial pathogens.

Surrogate parameters Monitoring so urce water for warning of potential, often intermittent, contamination clearly requires timely information that refl ects actual circumstances. In most cases, this impl ies rhe need fo r online, continuous monitoring in real -rime. M ost water quali ty parameters, particularly microbial, are nor amenable to continuous real-rime measurement. Hence, effective operational surrogate parameters amenable to chis should also be developed and mon itored wherever possible throughout the system along with trigger levels fo r actions fo r immediate adjustment and corrective action.

Some useful surrogate parameters include rain fa ll events, turb idity, chlorine residual, flow, pressu re, pH, particle counts, and cond uctivity. These parameters are nor absolute, h owever, so it is essential chat relationships between operational surrogates and water quality parameters be validated and estab lished through systemspecific investigations under a variety of cond itions (i .e. seasonally, during events, when using new treatment chem icals or changes).

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Box 4. Respond ing to Customer Compla ints.

In 1993, Milwa ukee, USA, experienced a cryptosporidiosis outbreak. Difficulty experienced in treatment operation resulted in treated water turbidity reaching levels much higher than normal. Not only did operators not respond to the turbid ity spike that was occurring, they a lso did not recognise the sig nif icance of the increase in consumer complaints that accompanied it. In this instance consumer complaints dramatically increased to nearly 50 complaints one day (against a background of less than 5) around the time of the turb idity spikes suggesting that the quality of water was substantially impa ired (Hrudey and Hrudey 2007). Unfortunately these conditions, ind icative of a serious water quality problem, were not recognised at this time a nd the chance of effective response and immediate corrective action was lost. A number of other documented outbreaks involved some level of consumer detection of problems, usually by sensory means (H rudey and Hrudey 2007) .

Consumer satisfaction monitoring Monitoring consumer satisfaction is another important surveillance mechanism that can p rovide valuable and timely information on potential problems rhar may have gone u n identified th rough monitoring d rin king water q uality (NHMRC 2004). Because consumer feedback is directly related to the quality of drinking water at the consumer's tap, they often can be the fi rst to identify char something is un usual with rhe water. For consu mers, ch anges from rhe no rm are particularly not iceable.

In some waterborne disease o utbreaks, consumer comments and complaints have accompanied changes in water quality or quantity that ultimately led to the outbreak. The sign ifica nce of these complaints, however, went unnoticed by the water supplier, as exampled in Box 4, thereby missing an additional opportunity for early recognition of contamination and initiating any corrective actions.

Consumers are located at every point in a d istribution system and thus potentia lly provide timely in fo rmation o n contamination. An effective consu mer complaint and response system should have close links to operations. Complaints of unusual water quality are important and any complaint of illness warrants particular attention (Whelton and Cooney 2004).

Ultimately, wh at is required are monitoring programs based on systemspecific evidence wh ich recognise the in herent limitations and cap abilities o f monitoring, and p rovide a closer lin kage between monitoring data an d risk management. Essentially, a strategic water quality monitori ng system involves an integrated program of source water, p rocess control and event-driven monitoring when the system is being increasingly challe nged, sup plemented with verifying the effectiven ess of d istr ib ution system preventio n programs, and monitoring co nsu mer satisfaction.

This combination of u nderstanding the contaminant ch allenge to the system, the treatment capability of the system, utilising real rime monitors of treatment performa nce, recognising and respond ing to events, and prevent ing co ntam in ation in the distribution system should provide much greater protection of p ublic health and is a more effective strategy for prevention.

Acknowledgments Financial support from the Australian Cooperative Research Centre fo r Water Quali ty and T reatment, the Canadian Water Network, Alberta H ealth and Wellness, an d the Narural Sciences and Engineering Research Council of Canada are gratefully noted.

Conclusions Overall, d rinking water quality monitoring plays an essential role in drinki ng water safety rhac is often nor fully exploited. A water su pplier wish ing to maximise its ability to detect contaminated drinking water and provide greater p ublic health protection must ensure that monitoring programs are effectively designed to support collecti ng data that increase understanding of an individual water supply system and the risks that are present, both in normal operation and during events.

Journal of the Australian Water Association

The Authors Samantha Rizak is a Research Fellow in the Department of Ep idemiology and P reventive Medicin e and Cooperative Research Centre for Water Quality and Treatment, Monash University, Alfred H ospital, Melb ou rne Vic 300 4. samanrha. rizak@med.monash. edu.au.

Dr Steve Hrudey is a professor of environ mental health sciences and Associate D ean of the Scho ol of P ub lic H eal th, University of Alberta, Edmonton, Canada. sreve.h rudey@ualberra.ca

References Angulo FJ, Tippen S, Sharp DJ, Payne BJ, Collier C, Hill JE, Barren TJ, Clark RM, Geldreich EE, Donnell HD, Swerdlow DL. (1997). A community waterborne outbreak of salmonellosis and the effectiveness of a boil water order. Am. J Public Health 87(4): 580-584.

Ashworth B. (2005). Incident Management in Practice. Water May: 32-33.

Clark RM, Geldreich EF, Fox KR, Rice EW, Johnson CH , Goodrich JA, BarnickJA, Abdesaken F. (1996). Tracking a Salmonella serovar typhimurittm outbreak in Gideon, Missouri: role of contaminant propagation modelling. J Water SRT -Aqua 45(4) : 171- 183.

Craun GF, Calderon RL. (2001). Waterborne disease outbreaks caused by distribution system deficiencies. journal ofthe American Water Works Association 93(9): 64-75.

Geldreich EE, Fox KR, Goodrich JA, Rice EW, Clark RM, Swerdlow DL. (l 992). Searching for a water supply connection in the Cabool, Missouri disease outbreak of Escherichia coli Ol57:H7. Water Res. 26: 1127-1137.

Gullick RW, Grayman WM, Deininger RA, Males RM. (2003) . Design of early warning monitoring systems for source waters. journal

pp. Website [accessed Dec 14 2006] : http://www.norrhbarrlefordwarerinquiry.ca LeChevallier MW, Gullick RW, Karim MR, Friedman M, Funk J E. (2003). The potential for health risks form intrusion of contaminants into the distribution system from pressure transients. J Water Health 1(1): 3-14.

N HMRC (2004) . Australian Drinking Water Guidelines.Canberra, ACT: National H ealth and Medical Research Council. Website [accessed Dec 14 2006] : http://www.nhmrc. gov.au/ publications/synopses/eh l 9syn. h rm O'Connor DR. (2002) . Report ofthe Walkerton

Inquiry. Part 2. A Strategy for Safe Water.

Toronto, T he W alkerton Inquiry: 582 pp.

Website [accessed Dec 14 2006]: h rrp:/ /www.artorneygenera1 .j us.gov.on.ca/ english/abour/pubs/wa!kerron Rizak S, H rudey SE (2007a). Evidence of water quality monitoring limitations for outbreak detection. Environmental Health, 7(1 ): 11-21.

Rizak S, Hrudey SE (20076) . Developing

Strategic water Quality Monitoring Systems for Drinking Water Safety. Research Report.

Cooperative Research Centre fo r Water Quality and Treatment. In press.

Sturdevant Rees PL, Long SC, Baker R, Bordeau DH, Pei R, Barren PK. (2006). Development

ofEvent-based Pathogen Monitoring Strategies for Watersheds. Denver: A WWA Research Foundation.

Swerdlow DL, Woodruff BA, Brady RC, Griffin PM, Tippen S, Donnell HD, Geldreich E, Payne BJ , Meyer A, Wells JG, Greene KO, Bright M, Bean N H , Blake PA. (l 992). A waterborne outbreak in Missouri of Escherichia coli O157:H7 associated with bloody diarrhea and dearh. Ann. Intern. Med. 117(10): 812-819.

Whelton AJ, Cooney MF. (2004). Drinking water surveillance: we need our customers to complain . journal ofthe American Water Works Association 30(11): 3-7.

WHO (2004a) . Water Safety Plans. WHO Guidelines for Drinking Water Quality 3rd Edition. Geneva: World H ealt h Organisation: 54-88 (Chapter 4). Website [accessed Dec 14 2006]: http://www.who. inr/water_sanirarion_healrh/dwq/gdwq3/en/ WHO (20046) Rolling revision of rhe WHO Guidelines for Drinking-water Quality.

Website on managing chemicals [accessed Dec 14 2006]: hcrp://www.who.int/ warer_sanirarion_healrh/dwq/chem icals/ managchemic/en/index.hrml

ofthe American Water Works Association 95(11): 58-72.

Hrudey SE, Hrudey EJ. (2004) . Saft Drinking

Water - lessons from Recent Outbreaks in Affluent Nations. London: IWA Publishing: 5 14 pp.

Hrudey SE, Hrudey EJ . (2007). A nose for rrouble - the role of off-flavours in assuring drinking water safety. Water Science and Technology, 55(5): 239-247.

Hrudey SE, Walker R. (2005). Walkerton - 5 years later. Tragedy could have been prevented. Opjlow. 31(6): 1,4-7.

Kramer M H , H erwaldt BL, Craun GF, Calderon RL, Juranek DD. (1996).

Waterborne disease: I 993 and I 994. journal

ofthe American Water Works Association.

88(9): 66-80.

Laing, R. D . (2002). Report ofthe Commission of

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.fereed paper

RUNOFF ENHANCEMENT IN WATER SUPPLY CATCHMENTS P B Hairsine, J M Perraud, T W Ellis Abstract Runoff enhancement farms (REFs) are rural enterprises chat generate additional runoff by decreasing che permeability of soils co maximise che proportion of rainfall chat becomes runoff. While these enterprises have been extensively used in semi-arid environments both in Australia and overseas, they have received liccle attention in eastern states. This paper reviews the prospects for using runoff enhancement farms within water supply catch ments and provides some analysis of their economic viability and long-term yield. Our analysis suggests chat such REFs cou ld produce significant supplementary flow co ex isting reservoirs in both wee and dry years and produce an income chat compares favourably co existing land uses. Barriers co full-scale operations include the absence of institutional schemes for water agencies co pay for additional runoff generated by runoff enhancement farms (i.e. a screamflow market) and a full analysis of che economics of such enterprises .

Introduction During 2005 , one of the d riest years on record, around 8 million megalicres of rain fell o n the catchment of Sydney's Warragamba reservoir, potentially enough co fill che reservoir four times. Of co urse chis didn't happen because most of che rain soaked inco che soil and lacer evaporated. I n dry years che proportion of rainfall becoming runoff is smaller than in wee years and chis magnifies the influence of below-average rainfall on water security.

In chis paper we exp lore the prospects for runoff enhancement techniques co increase che screamflow in water supply catchments in eastern Australia. The analysis presented suggests chat such enterprises may be viable in creating additional runoff co existing water resources infrastructure.

"Runoff en hancement" or "runoff inducement" has been extensively used co increase surface water flows throughout history (Myers, 1975). There are various techniques for achieving ch is - all decrease che permeability of the soil surface, thereby producing increases in the proportion of rainfall chat becomes runoff. Runoff enhancement has been extensively used in

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Figure 1. A runoff enhancement farm in south west Western Australia (photo: David Stanton, Western Austra lian Department of Ag riculture). semi-arid and arid lands for water supplies (Hillel, 1967, Fink et aL., 1980, and Boers and Ben-Asher, 1982), in the enhancemenr of fo rest growth (Li et aL., 2006) and in micro-catchment systems associated wirh agroforescry.

Runoff enhancement systems are varied in materials and design. Processes used co reduce wacer infilcracion into che soil include che addition of waxes co the surface, che use of sunlighc- resiscant plastic films and the compaction of bare soil.

Richardson et al. (2004) provide a recent review of these methods. This review fou nd chat techniques are normally adapted co a particular application and cheir selection is frequencly influenced by the local soil cype, especially concerning the sealant's abi lity co treat the surface so il texture. Frasier and Myers (1982) provide a handbook of methods of soil treatment including earthworks and related drainage layouts.

Mose runoff enhancement systems have been employed in semi-arid or arid environments in micro (<1000 m 2 ) co small (<2 ha) configurations (Boers and BenAsher, 1982). These catchmen ts generate additional runoff chat either is used for watering high value trees or crops, or provides secure stock water (e .g . Burdass, 1975) . Typically the catchment is fenced co exclude stock damage and che surface is shaped co drain co a small water storage basin .

In Australia chere is extensive experience wich runoff enhancement (Laing, 1981).

Mose of chis experience has been accrued through more chan thirty years of trials and experience in Western Australia. In numerous water supply cacchmencs of farms

Journal of the Australian Water Association

and small rural towns, surface soils were purposely compacted co increase surface runoff (Stanton , 2005). Because the practice uses what would otherwise be undeveloped agricultural or grazing land, the term "Runoff enhancement farms" or "REFs" has come into use. In 1973, there were around 2,500 roaded (i.e. b are and compacted) catchments on fa rms in Western Australia (Burdass, 1975) and they remain extensively used by small rural towns and large vineyards today (David Stanton, Western Australian Department of Agriculture, pers. com.) . Figure 1 shows an aerial view of one of these systems and the associated farm storage dam. This system uses co mpacted bare earth and a small reservoir co provide a secure an imal watering supply.

The use of larger (> I 00 hectares) REFs is possible but it appears cheir use has been limited by che relative abundance of alcernacive wacer supplies.

Scope for Application of REFs Inside Water Supply Catchments In eastern Australia many wacer supply reservoirs have been at record low levels in recent years. As a consequence there has been considerable public debate and m any technical investigation s concerning alcernacive or complementary water sup plies. Runoff enhancement w ithin che water supply catch menr is one complem enrary approach char has received liccle attention. In chis type of application, REFs would noc include local dams as all runoff would be scored in che main reservoir of the catchment.

T able 1 provides a summary of che opportunities and obstacles for REFs in chis environment. Enterprises based around these techniques compare favourably wich

A few percent ofgrazing land converted to impermeable run-off could produce significant extra flow to existing reservoirs.

technical features ~

water supply alternatives such as desalination and access to new groundwater resources. O ne major opportuni ty is rhar REFs rake advantage of rhe existing water treatment and delivery infrastructures, with minimal energy inpu t.

T he major issues are that there are no current mechanisms for rhe payment for production of additional runoff by such enterprises, and that rhe econom ic viab ility of such enterprises in this application is unproven. Most water resources legislation co nsiders rainfall to belong to the stare. In practice, on ly runoff is regulated by providing limits to rhe amount of rainfall harvested by measures such as fa rm dams and through licensing of su rface and groundwater abstraction (see McKay, 2003 for discussion and note this is in a policy environment of current change). REFs convert more rainfall to runoff for downstream use, thereby providing more off sire benefits than considered normal in current legislation .

T here are several issues ro be resolved before the overall viability of ru noff enhancement systems ro increasing the quanti ty of water in urban catchments can be fully assessed. In this paper we discuss some of these issues.

Viability and Reliability of Runoff Enhancement Enterprises REFs are most commonly found in arid and semi-arid settings (Boers and Ben-Asher, 1982). In these environments sufficient rainfall falls for addi tional runoff to be harvested even in relatively dry years (Frasier et al., I 979) . T he relatively low cost of land here contrasted ro higher rainfall areas contributes ro the economic success of these systems.

In theory, an REF enterprise would produce income as a product of rhe volume of additional runoff rhar is generated and its price per volume. The volume of runoff is a product of the area of the REF and the rainfall less rhe losses. In periods of low rainfall, runoff is expected to be lower but the price of a unit of water should be greater, rending to make income si milar in all years. T his effect is exp lored in a case study presented below.

Losses are the portion of rainfall chat does not become runoff. In natural catchments these are typically of the order of 95%, though chis proportion varies greatly with rainfall, ocher climate factors, so ils and vegetation (Hill et al., 1998). Losses are associated with rainfall interception by vegetation (and subsequent evapo ration; typically <15% of rainfall in agricultural land) and infiltration into the soil lost to soil evaporation and plant transpiration (the remainder), while deep drainage (typically

- - --

.... -

Table 1. A summary of potential opportunities and obstacles in relation to runoff enhancement systems if used in water su pply catch ments.

Potential opportunities

Potential obstacles

• Additional runoff can be generated within water supply catchments without the need for change in land tenure.

• There is no current mechanism to pay land owners for the additional runoff they generate.

• Existing water resources infrastructure is used, including reservoi rs, water treatment plants and distribution networks.

• The economic viability of such enterprises is unproven in this setting.

• Grazing land that is of low productivity may be most suitable.

• Substantial income to farming enterprises may be realised.

• Potentially less groundwater recharge in important salt generating areas.

• Less groundwater recharge will occur in proportion to the area treated - this will be a good outcome for areas where control of recharge is im portant to control downstream salinity and a poor o utcome where the recharge of g roundwater resources is important.

<10% of rainfall) adds to groundwater and may ul timately contri bute to srreamflow ar a later stage. In REFs, vegetation is absent and infiltration is reduced to an absolute minimum. Researchers have reported loss rares of approximately 5%, so that runoff is increased many fold in these areas (see reviews by Frasier et al., 1979 and Richardson et al., 2004). Furthermore, in REFs runoff occurs for small rain fall events rhar wo uld not produce any runoff for untreated areas. In all cases the runoff rhar enters rhe natural drainage system is subject ro further losses as ir resides in storages or moves down the drainage system and these losses will reduce total water yield so mewhat.

A Case Study of the Viability of a Runoff Enhancement Farm There are rwo key measures of the success of a REF: 1. The income of an enterprise based around REF. T his measure is a key input ro rhe assessment of viability to the landholder, who is likely to compare rhe income, and rhe reliab ility of rhe income, to char obtainable from alternative uses of the land.

2. The total vol ume of additional runoff made available to the water supply. T his measure may be especially important in dry years and is a key input to the assessment of the water supply agency.

The following case study is an explo ratory analys is in which we calculate these rwo measures for a location within the Warragamba catchment, Sydney's main water supply. We use actual climate data,

• The water quality from REFs varies greatly and pre-treatment immediately downstream may be necessary.

• Potential aesthetic concerns about large areas of bare treated soils.

• Peak flows in floods may be exacerbated though this effect can be migrated by the inclusion of on-farm wetlands in REFs. • Potential environmental concerns about large areas of bare treated soils. These areas will have no biodiversity and decommissioning will need to be considered.

• There is little experience in "farming water" in eastern Australia and investment will be required to develop appropriate technology.

runoff model parameters from the literature and plausible pricing models fo r chis case srudy.

The water pricing model we use is hypothetical bur is loosely based on existing pricing schemes (IPART, 2005; Sydney Water Corporation, 2006), and the dam level thresholds triggering water restrictions in recent history. Figure 2 shows the three functions we use as input to this analysis, where the water unit price is related to the vol ume of water available in the reservoir.

When the reservoir has lower levels the price per uni t water is likely to increase as supplementary options, including desalinisarion and grou ndwater pumping, are considered. T he upper an d lower prices are arbitrary bur serve to illustrate the possible income of such enterprises and co mpariso n ro other water supply supplementation methods. As a consequence rhe reader shou ld interpret rhe income predictions as indicative only and subject to major changes as a result of the operation of the actual water marker.

In this case study we use the 1960 to 2005 rainfall record for Moss Vale, wh ich is adjacent to the portion of the catchment dominated by pastures (Bureau of Meteorology, 2006) as rhe input to the runoff model. This record contains substantial periods of below and above average rainfall.

Dam storage levels and stored volume data were obtain ed from rhe Syd ney Catchment Authority. The few gaps in rhe dam vol ume data were filled, using linear changes in storage, for rhe purpose of this paper. Here we use a very simple runoff model sim ilar

Journal of the Australian Water Association

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JUNE 2007 73

technical features

co che rational method using an initial loss and chen a portion of the remaining rainfall chat becomes runoff. The model simulates runoff chat would have occurred on a daily basis for both created and uncreated areas.

This model has cwo input parameters: che runoff generation th reshold and the slope of the continuous loss compared with rainfall.

The model was calibrated so chat predictions of daily runoff approximated chose in che published field studies as described below. Figure 3 shows model results where che input rainfall-runoff parameters for the uncreated area were sec co 2.5 mm and 0.7, and co 0.5 mm and 0.05 for the wax-treated area, based on the summary cables in Richardson et al. (2004).

It is acknowledged that chis is a simple model chat does not explicitly describe baseflow processes. However these are the only available models chat have been calibrated for such created systems at the hillslope scale.

Figure 3 is presented as a time series of inputs and outputs comprising a) the an nual rainfall, b) che storage levels of the Warragamba dam, and c) the predicted farm income per unit created area of REF, using the price functions shown in Figure 2. Income is calculated on the basis of additional runoff generated above chat chat would have been produced from uncreated areas. This preliminary assessmenc is escimaced from long term studies where surface runoff and groundwater would have concribuced co che scream flow.

Note that the predictions in Figure 3c suggest chat such enterprises will have significanc income in all years in both che "Best" and "Intermed iate" water price models. If the "Worsc" water price model is adopted then income is only significant when reservoir levels are low. Figure 3 also illustrates chat income is generally higher in low reservoir years due co the combined effects of che slope on the water price function, che rainfall runoff function and the slope of the rainfall co runoff relationship. This effect would be useful in providing a steadier coca! far m income as cradicional agricultural production outside che area of che REFs is likely co be reduced in low reservoir periods. The magnitude of the REF income per unit land area compares well with most agricultural uses, though the economic attractiveness of a water enhancemenc encerprise will depend upon nee income after capital and maincenance coses.

To assess the REF land area required for significanc gains in runoff co be obtained within the encire reservoir catchment, we combined che range of expected rainfall 74 JUNE 2007

Water

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Note th at i ncome is only assumed to be generated for additional runoff generated.

with the runoff model. T aking the temporal range of annual rai nfall in the grazing portion of the catchment as 507 co 1686 mm (1960 co 2005), che runoff coefficienc of 0.8 (a conservative estimate allowing for off-farm losses) and che full sup ply capacity of the reservoir as 2027 gigalicres, then che

Journal of the Australian Water Association

area of REF required co add 1% of capacity co the scored volume in che Warragamba reservoir ranges from 1500 co 5000 hectares. While chis is a significanc area, 0.2 co 0.6 percenc of che total cacchmenc, ic is small in comparison co the size of the pastured portion of the catchment.

technical features

Other Factors to Consider in the Design of Runoff Enhancement Farms There is considerable variation in the qualiry of the runoff generated in REFs and a review of so me of these findings is presented in Richardson et al (2005). Two water quality issues need robe assessed for any application: the mobilisation of soil and related catchment pollutants and rhe mobilisation of rhe sealant itself.

Compacted catchments have been found ro yield considerable amounts of sediment (Cluff, 1975 an d see example see turbid water in srorage in Figure 1). The mobilisa rion of poll utants can be greatly reduced through the use of sealing agents includi ng waxes and polymers. In Western Austral ia there are currently trials concern ing food-grade waxes (David Stanton Western Australia Department of Agriculru re - pers. com.).

There may be scope for water supply co nfigurarions that comb ine runoff enhancement areas with small wetlands or bands of filtering vegerarion. These systems could serve to greatly increase runoff while providing so me local enhancement of water quality and the creation of local habitat. It is expected that these sysrems would be configured to slow the delivery of rapid downstream runoff so that flows are less "peaky" and rherefore less erosive within rhe natural drainage system.

Esrimares of the costs of rhese trearments are likely to vary between locations, as in flue nced by soil preparation, soil type, labou r costs and stock exclusion. A recent study by Li et al. (2006) estimated plastic fi lm costs of approximately $3000 per hectare with the film having a lifespan of between 5 and 8 years. Richardson et al.

(2004) reported smaller costs for waxed based systems and the longevity of the surface of greater than 5 years. The actual coses of these systems will depend on local co ndi tions and the development of skill and techniques in local enterprises.

Concluding Remarks The analysis presented in chis paper provides some of rhe basis fo r an assessment of runoff enhancement farms borh as ro rheir porential viabiliry as farming enterprises and as their significance as contriburors of supplemenrary runoff ro urban reservoirs. Ir suggesrs chat if a mechanism for paying for addirional runoff can be devised such enterprises could be attractive to at least some land managers.

T he viability of these enterprises will depend on several local factors some of which have not been considered in detail here. Specifically, the income provided by REFs will be greatly influenced by rhe actual market available fo r sel ling addirional runoff. Other factors to be considered include invesrigation of the required changes to the water market regulation, legislation ro permit payment to privare landholders for additional runoff generared, a derailed invesrigarion of the economics of such enterprises, and intensive monitoring of the quality of runoff generared in specific environments. Furrhermore, ir is nored char experience and measurement of the outcomes of large (thousands of hectares) REFs is nor available, so that future developments should be appropriately cautious.

Frasier, G.W., Cooley, K.R. and Griggs, J.R. (1979) Performance Evaluation of Water Harvesting Catchments. journal ofRange Management 32(6):453-456 Frasier G .W. and Myers L.E. , 1983. H andbook of water harvesting - Un ired Stares Department of Agriculture, Agriculture

Research Service - Agriculture handbook No. 600, 45 p.

ofthe Water Harvesting Symposium, 1974,

Hill P.I., Mein R. and Siriwardena L. I 998.

How much rainfall becomes runoff?: Loss modelling for flood estimation. CRC for Catchment Hydrology Industry Report 98/5.

Available ar http:/ /www.carchmenr.crc.org.au/ pd fs/ industry I 99805.pdf.

Hillel, 0., 1967. Runoffinducement in arid lands. Final Tech. Rep. USDA Projecr A 10-SWC-36. Rehovot, Israel, 142 pp. !PART , Independent Pricing and Regulatory Tribunal of New South Wales, Prices of the water supply, wastewater and srormwarer services (2005), Schedule 2, Water Supply Services, Bulk Raw Water, p I 06, ISBN I 920987 36 3, Available at http://www.iparc. nsw.gov.au/files/ Final%20Derermination%2 0and%20Reporr%20%20SWC%20 H WC% 20SCA%20-%20website%20document.PDF Laing, I.A F. 1981. Rainfall Collection in Australia. In Rainfall Collection for Agriculture in Arid and Semi-Arid Regions: Proceedings of a workshop hosted by the University of Arizona, USA and the Chapingo Postgraduate College, Mexico. p61 -66.

Edited by GR Dutt, CF Hutchinson and M Anaya Garduno. Farnhan Royal, CAB, 1981.

Li, X.-Y, Shi, P.-J., Su n, Y.-L., Tang, J. and Yang, Z.-P. 2006. Influence of various in sim rainwater harvesting methods on soil moismre and growth ofTamarix ramosissima in the semiarid loess region of China. Forest Ecology and Management. 233( 1) 143-148.

McKay, J . 2003. Who owns Australia's water elements of an effective regulatory model.

Water Science and Technology 48(7) I 65-172 .

Myers, L.E. 1975. Water Harvesting- 2000 BC to 1974 AD. In Proceedings ofthe Water Harrmting Symposium, 1974, Phoenix Arizona. pl-7. Berkley, California. Ag. Research Service, Western Region, 1975.

Richardson, L., P.B. Hairsine and T.W. Ellis.

2004. Water farms: A review ofthe physical

Phoen ix Arizona. P8-25. Berkley, California.

Ag. Research Service, Western Region, I 975.

Bureau of Meteorology, 2006. SILO Patched Point data for station: 68045 MOSS VALE (HOSKINS STREET) Lat: -34.54 Long: 150.38. Extracted from Silo on 20060824. http://www.bom.gov.au/silo/ Cluff, C.B. (1975) Engineering Aspects of Water Harvesting Research ar the University of Arizona. In Proceedings ofthe Water Harvesting Symposium, 1974, Phoenix Arizona. p27-39. Berkley, California. Ag. Research Service, Western Region, 1975 .

Fink, D.H ., Frasier, G.W. and Cooley, K.R. ( 1980) Water H arvesting by Wax-treated Soil Surfaces: Progress, Problems and Porenrial. Agricultural Water Management 3:125- 134.

T echnical report 04/6 (available at http://www.carchmenr.crc.org.au/ pd fs/ technical200406. pdf) Stanton, D. 2005. Roaded catchments to improve reliability of farm dams. Bulletin 4660 of the Department of Agriculture Western Australia ISSN 1448-0352.

Available at http://www.agric.wa.gov.au/ pis/ porral30/ docs/FO LO ER/I KMP /LWE/ WATER/ENG/ROADEDCAT CH_BULL. PDF Sydney Water Corporation (2006), Usage charges 2006-2007, SW 226 06/06, Available at http://www.sydneyv,ater.com.au/ Publications/_download.cfm?DownloadFile= FactSheets/UsageCharges. pdf

Acknowledgments The authors gracefully acknowledge rhe co nrriburion of rhe Sydney Catchment Authority for providing the Warragamba dam volume data and David Stanton of the Western Ausrralian Department of Agriculture for information concerning the roaded catchments in WA. We also acknowledge the constructive reviews of David Mitchell, David Power, Albert van Dijk and David Post.

The Authors Peter B Hairsine is a research scientist and leader of the water quality and environmental flows group; Jean-Michel Perraud is a hydrologic modeller and software engineer and Tim Ellis is a research scientist, all ar CS IRO Land and Warer, Canberra (perer. hairsine@csiro.au) .

References Boers Th.M., and Ben-Asher J. 1982. A review of rainwater harvesting, Agric. Water Manage. , Volume: 5, (1982), pp. 145-158 Burdass, W.J. 1975. Water H arvesting for Livesrock in Western Australia. In Proceedings

aspects ofwater harvesting and runoff enhancement in rural landscapes. CRC C H

Journal of the Australian Water Association

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JUNE 2007 75

LARGE COMMERCIAL RAINWATER HARVESTING PROJECTS Australia is in the m idst of the worst drou ght on record. Dam levels are close to all rime lows for most majo r centres. In response, severe water restrictions have been imposed for almost every part of the country.

Water Business aims to keep readers alert to business news and new product releases within the water sector. Media releases should be emailed ro Brian Raulr at brian.raulr@halledit.com.au or Tel (03) 8534 5014.

Generally the response has been to lament the fact that we 'live on the driest continent on Earth'. It is used as justification for energy inten sive desalinatio n plants and major recycling schemes. However, it is often overlooked char whilst the catch ments for rhe dams are in rhe d riest pares, rhe majority of Australians live in areas with an nual rainfalls of up to 1,200mm. This is nor dry.

by subsidy schemes with rebates from $50 0 to $1,500 available per domestic installation.

The Australian population has responded to the water crisis by adopting residen tial rainwater ranks. W hilst desalination and recycl ing ('drinking sewage') remain deeply u npopu lar, there are currently th ree to six month waiti ng rimes to get a domest ic rainwater rank in stalled. Demand is fuelled

Yer one area ofren overlooked, and not specifically addressed by the rebate schemes, are commercial rainwater harvesting options. Collecting rainwater fro m large roof areas can lead to sign ificant water savings at economically far m ore attractive parameters than for residential installations.

Rain Vau It

TM -

AWA wishes to advise readers that Water Business information is supplied by third parries and as such, AWA is nor responsible for th e accuracy, o r otherwise, of the information submitted.

Rainwater Reuse System

There is considerable scope for large commercial rainwater harvesting projects.

Based on the experien ce of rhe au thor, within existing faci lities, 25% of Australia's urban water consumption could readily be reduced through efficiency measures. Of the remainder, another 8% could be supplied by commercially viable rainwater harvesting schemes even under cu rrent low water prices and price d istortions.

Football stadiums can have ideal roofs for rainwater harvesting.

The goal is co build an integrated water supply network where rhe large damsupplied systems work hand-in-hand with thousands o f m ini-dam supplies fou nd in

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JUNE 2007

Water

Journal of the Australian Water Association