Water Journal February 1994

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AUSTRALIAN WATER & WASTEWATER ASSOCIATION

FEBRUARY 1

AUSTRALIAN WATER & WASTEWATER ASSOCIATION

Volume 21, No 1 February 199, Editor Bob Swinton

CONTENTS

Editorial Correspondence

ASSOCIATION NEWS President's Message From the Executive Director

2 4

From the Branches

5

Women in Water

16

MY POINT OF VIEW Bush Fires and Catchment Management

3

Peter Hughes

Focus on Western Australia Coastal Eutrophication: Prevention is Better than Cure The Perth Coastal Water Study

22

DA Lord •

Modifying the Phosphorous Cycle to Achieve Management Objectives in the Oyster Harbour Catchment

28

D M Weaver, LJ Pen, A E G Reed •

Large Scale Catchment Modelling to Predict the Effects of Land Use and Climate

M Sivapalan,

Sodic Soils and Water Quality: Are They Related?

Continuous Monitoring of Sewage and Industrial Effluents

R J O'Halloran,

33

R Viney

T M Skene, J M Oades

Advertising Sales & Administration Margaret Bares Tel (02)413 1288 Fax (02)41 .l 1047 A\XI\Y/ A Federal Office Level 2, ~~ Hampden Road, Arrarmon PO Box 388, Artarmon NS\XI 2064

Editorial Board f R Bishop, Chairman MR Chapman, M Muntisov, P Nadebaum P Draayers, JD Parker, A JPriestley GA Holder, B Lade, W J Dulfer

FEATURES •

4 Pleasant View Crescent Glen Waverley Vic .l 150 Tel/Fax (03) 560 4752

38 17

H Pilkingron , B A Sexron

REPORTS

Branch Correspondents ACT - Alan \Y/ade Tel (06) 207 235 0 Fax (06) 207 6084 New So uth \Y/ales - Mitchell Langinescra Tel (02)4129974 Fax (02)4 129876 Northern Territory - Mike Burgess Tel (089) 82 7111 Fax (089) 82 7430 Queensland - Lyndsay Chapple Tel (07) 835 0222 Fax (07) 832 6335 South Australi a - Phil Thomas Tel (08) 259 0244 Fax (08) 259 0228 Tasmania - Ji m Stephens Tel (002) 31 0656 Fax (002) 34 7334 Victoria - Mike Munrisov Tel (03) 600 1100 Fax (03 ) 600 1300 Western Aus trali a - Tony Hend ry Tel (09)/497 l 344 Fax (09) 497 1281

WATER (ISSN 0310-0367)

Regional Conferences Drinking Water Quality - Technical and Management Issues

8 14

is published six rimes per year February, April, June, August , October, December by

40

Australian Water & Wastewater Inc.

P Thomas Selling Australian Environmental Know-How in Asia

E Wajon, EA Swinron

ARBN 054 253 066 PO Box 388, Arrarmon NSW 2064

DEPARTMENTS International Affiliates

10

Books

21

Industry News Products

42

Meetings

44

43

OUR COVER Rehabilitari on of a bauxire mine in rhe Darling Ranges of \X/esrern Australia: First, the mined-our sire awa iting re-contouring and replacement of the scored topso il before deep ripping; second , five years lacer, already with dense cover. The third photograph (taken fro m adjacent unmined forest) shows young jarrah fo res t after onl y eight yea rs.

Alcoa of Australia Ltd, in conjunction with the \XI A Department of Conservation and Land Managemen t, pioneered the program , which required R&D to suir the_specific soil and cli mar ic condi tions, and t0 compensate fo r phyrnphrhora cinnamoni.

The ai m is nor on ly co resrore the ecology bur co protect che water resources.

The paper on Catchment Modelling (page 33) desc ribes only one aspect of rhe research supporred by the company. Alcoa is the only mining company in the world tO be li sted on the United Nations Global 500 l?oll of Honour for environmental achievement.

Photographs co11rtesJ of Alcoa of Amtralia.

·

Federal President Richard Marks Executive Director Chri s Davi ~ Australian \Y/arer & \Y/asrewarcr Association assumes no responsibility fo r opinions or statements of facts expressed by contributors or advertisers and editorials do nor necessarily represent rhe official policy of rhe organisation.

Display and classified advertisements are included as an informational service

to

readers and are reviewed

by the ediror before publication ro ensure their relevance ro rhe water en vironment and ro the objecrives of rhe Association.

All material in \Vi1ter~s copyright and should nor be reproduced wholly or in part without the written perm ission of the Ediror.

Subscriptions Water is senr to all members of the A\Y/\Y/ A as one of

the priv ileges of membership. Nonmembers can obtain lflater on subscription at an annual subscription rare of $30, this includes cost of surface mail postage.

TECHNOLOGY

CONTINUOUS MONITORING OF SEWAGE AND INDUSTRIAL EFFLUENTS RJ O'Halloran *, NH Pilkington, BA Sexton Abstract A concinuous on-line sewer monitoring sysrem has been developed by a mulri -disciplinary ream in CSIRO for monitorin g a suire of basic physico-chemical paramerers (re mperarure, pH, conducriviry, rurbidiry and dissolved oxygen), whi ch reflecr rhe bulk properries of sewage. Appropri are sensor are mounced in a flow manifold fed by a submersible mucracing pump. Th e inherenc scouring acrion of rhe flowi ng effluenc was found co minimise fouling build-up, and rhe sysrem has been proven to operare reliably in a broad range of effluents for several momhs wirh lirde anencion.

Mose sewer discharges will affecr ar lease one of rhe variables measured , so rhe sysrem is abl e to derecr a wide variery of discharge evenc , ranging from hoc wash warer to elecrroplaring wasres. le can police discharges in induscrial esrares, monitor diurnal rrends in domes ric carchm encs, and can be used to oprimise rreacmenc planc performance. Field rrials have been conducred in a wide range of sewage effluenrs, where ir successfu ll y derecred illegal and unsuspecred discharges.

The sysrem is compacr and readily porcable, and can be used borh ar fixed sires or as a mobile rrade wasre inspecr ion unir. Th e sysrem is now available commerciall y as rhe Sewer Seuti11el1•

Introduction The ci ry of Melbourne, rhe capiral of rhe scare of Vicror ia, has a popular ion approaching 3.5 million and suppom a wide range of indusrries. Melbourne Warer, rhe aurhoriry in charge of its water supply and sewage creacmenc, is responsible for accepri ng and rrearing a large vo lume of chis induscrial waste. Illegal or toxic discharges can compromise rhe safery of ewer workers, may resulr in damage to sewer infrasrruccure and biological rrearmenc processes, and have che pocencial to cau e serious environmental pollurion.

Sewer disc harge poi nts are sa mpl ed and ana lysed reg ularly, bur ir is likely char many harmful discharges will occur outside of the rim es ar which rhese samples are raken.

A continuous on-line moni toring system I. 5

~!ACE lnsrrumenrs Pry Ltd

WATER FEBRUARY 1994

was requi red to enable round-the-clock surveillance. There are severa l ways in which chis mighr be achi eved (Kugelman, 1982): • by co ll ecr in g regular or co mposite samples for subsequenc analysis • by analysing specific components cominuously • by monitoring more general properries of sewage On -lin e monitoring of fresh wacers fo r basic parameters is conducted extensively, and produces valuable data (Kohonen 198 5; Hanson 1981 ; and Schafer et al 1981 ). Sewage is a less traceable med ium , wirh fouling and blockages often preseming a severe problem . onecheless, various devices for monitoring sewage on-line have been developed, including chose wh ich meas ure BOD (F irrh and Cieslek, 1990), oxygen uprake (Wo ng and Smith , 1992), TOC (Ti eman and Wagner, Dr O'Halloran downloadinf!, data from a Sewer 198 1), COD (I anbo and Kunogi, 1981; Sentinel on trial at a Melbourne Suburban Rogalla et al, 1990), and a range of physico- \\1/WTP chemical paramecers (Hey, 1980; Dreicer et al, 1982; Bum and Daigger, 1990; and see robust means of sa mpl ing and sensing be rev iews by Sweeney, 1991; Bri ggs and adopted. Ir was decided to concencrare on Granan, 1990; J olley and Rivera, 1988 , parameters which cou ld be measured reliably 1989; Pin and Demon, 1982). The effecrive- and which would reflecr the bulk properties ness of monitoring accivaced sludge concinu- of sewage. The parameters chosen were cemousl y for a sui ce of parameters has also been peracure, pH, elecrrical conducrivicy, rnrbiddemonsrrared (Srephenson et al, 1981). i cy and disso lved oxygen (DO ). Mo se Despite the many reponed developments disc harges will affecr ac least one of th ese in rhe field of on-line sewage monitoring, no variables - effluents are ofren ac a different suirab le units were available comm erciall y. tern perarure to the sewer, many are acid 01 Consequendy, Melbourne \Xlacer approached alkaline, they may consist of highly saline 0 1 the CSIRO Inscirnce of lnduscrial Technolo- of fresh warer, many indusrrial effluents arE gies in early 1990 to see if ir was possible to turbid, and sewage DO is related to the level develop an on-line sensor system to derecc of biological activity. le has been reporcec hazardous cond irions in rhe sewers. Supponed elsewhere chat conducciviry and curbidiq by funding from the Urban \Xlacer Research g ive informa ri on abour dissolved and sus Associarion of Australi a, rhe CSIRO Division pended so lids load in wascewarer (Vand er of Chemica ls and Polymers and rhe Division borghc and \Xlollasr , 1990), and cha 1 of Materi als Science and Tech nology com- continuous monitoring of river warer wa: menced a feasibility study in October 1990. able ro detect rhe effecrs of illicit operarion: Jc was necessary to develop a continuous on warer qualiry (Kohonen, 1985). on-li ne sewer monitoring syscem capable of Spec ifi c analysi's for parricu lar con cami derecring un usual events which could be cor- nants (s uch as chrom ium or mercury) wa relared with pocencially harmful condirions. rejecred for a number of reaso ns - ir i During in irial discussions with both Divisions, and based on che experience gai ned at rhe CSIRO lower Plenty Field Sracion, it was *R J O'Halloran, CSIRO - Division o recommended ch ar rhe simp lest and most Marerials Science and Technology

unlikely co detect unknown discharges, it can require high capital and maintenance coses, and the measurement technology is often designed for clean environm ents and is not robust enough to give re liable results in complex matrices.

Experimental Sampling. Sampling of sewage has co contend wirh various problems since it contains a wide variety of contaminants, which may be dissolved, colloidal, suspended or immiscible material, and floating or solid objects. Fibrous materials can foul any projecting objects, and greasy or biological films quickly coat most surfaces. The problem was to keep sensors free of fouling so char rhey would function for lengthy periods wirh no maintenance. It has been found char a rapidly circulating effluent stream in narrow bore pipes can be used to continuously sample sewage (Whitby et al, 1983), and CSIRO were already using a similar approach for on1i ne monitoring of dissolved oxygen in sewage (Bridger, 1991 ; Pilkington, Bridger, Raper; 1993). We therefore decided to base our system on a flow-through design co minimise any build-up of fouling.

A range of pumps was trialled in raw sewage in domestic and induscrial wee wells, and ar treatment plants. Surface mounted pump/maceracors proved unsarisfaccory, with the inlet being blocked frequendy by foreign objects (a mop head and a shire were rwo of the most memorable). They were also prone to air leaks on the suction side, which upset sensor readings.

Sensors. An array of physico-chemical sensors for pH, temperature, conductivity, turbidity and dissolved oxygen was specially developed. A 4-electrode conducriviry flow ce ll, which is largely immune to effects caused by electrode fouling, was designed to replace the original 2-elemode unit, and chis has given excellent service. A customised fibre optic nephelomerer was employed , based on a CSIRO parented design. This was used to illuminate the flowing scream through the wall of rhe acrylic sensor module, thus eliminating direct contact with sewage and minimising fouling. The original DO electrode had a replaceable ceflon membrane, secured by an O-ring. This was prone co leakage, with the fast flowing sewage and pressure fluctuations in the flow manifold causing variable membrane pressures which gradually evacuated the elecrrolyte. It was replaced with one using a sealed membrane capsule, and chis has provided trouble-free operation.

The sensors presently comprise: • a planar, non-fouling pH elemode 2.

• a solid state temperature sensor • a custom-designed fou ling- resistant 4elemode conductivity cell.

• a fibre-optic infra-red nephelomecer (noncontacc cype)l.

• a sealed dissolved oxygen Clark cell 4.

Elecrronics for each sensor are integrated 18

onro a single circuit board, and temperature compensation of DO, pH and conductivity is done in software. The sensors are mounted in a modular flow manifold mad e from machined case acrylic (Figure 1). A constant flow of sewage above a critical velocity (1-2 m/sec) is maintained co preve nt fouling build-up. The see-through design enables visual inspeccion for signs of fouling, as well as a direct view of the effluent being rested.

Each sensor module is easily dismountable, thereby making maintenance a simple cask.

A slight accumu lation of biofilm on the working surfaces is normal, and it was found chat chis stabilises after several days. Therefore , che unit is preconditioned for this rime and then recalibrated before being ready for regular use. We have found chat periodic recalibration of sensors, and occasional repolishing of internal manifold walls or sensor replacement, is the only long-term maintenance required.

A HydroMACE 2000 dacalogger\ with cuscomised PC-based software, controls the sensor package and records data. Ir includes speech synthesis which reporcs alarm condicion s aucomarical ly to selected phone numbers.

Field Trials CSIRO Lower Plenty site. CSIRO Division of Chemicals and Pol ymers has a field station on the site of the former Melbourne Water sewage treatment plane at Lower Plenty. The sewage is from a mainly domesric catchment in Melbourne's noreheasrern suburbs. The first sewer monicoring procorype was developed and tested ar chis location before it was released for general field trials.

Remits. The parameters monicored showed a reproducible diurnal variation, which could be correlated with domestic habits in this shore catchment (Figure 2). The low flows during rhe night showed high DO and also high conducriviry (possibly due co infiltration of ground water). On a normal weekday, from 6. 30 a.m . onwards, domestic flows from toilers, kitchens and laundries commenced , with rising temperature, pH and turbidity. As the BOD load increased , DO dropped to almost anaerobic levels. The conductivity dropped because of dilution by mains supply water. Ar weekends, as shown in Figure 3, these patterns of activity were spread over a broader time scale, consistent with suburban habits. Industrial discharges (s uch as pH or conducrivicy events) were found to be very rare on chis primarily domestic sewer. The prototype was then relocated co CSIRO's Claycon site.

Clayton test site. The Clayton rest site was located at a wee well on the main sewer line through the CSIRO complex. (The sewer services a technological park, comprised of light industries). A ']'-shaped pipe was inserted inco the outlet main to provide a small weir for sampl in g purposes. The volume of chis weir was too small co provide

Figure 1 Th e .rewer monitoring system showing modular acrylic flow manifold, sensors and elel'tronic endosttre.

Vertical scales Friday, May 31. 1991

-

Cond 0-5mS/c m

.......•. pH 0-14

---- Temp 10-•o "C - --Turb().1000NTU - · · - 0.0 . 0-10~

/ ------f-1/ _____ ------------------• I

~

I :I ...... , ..l 1''---------c--------. __ _ . ' II I/ ., .I\.Jl :/\.

:I ,

J• ,. '

·'·--r_, --<.; . .__)'-.. . ,-. ___ ),1__

·, .,

'I

j\_,.... ..,.

.A-.r..._

-...Jv

'

12 15 T ime, hr

Figure 2 Sewer data from CSIRO Lower Plenty site on a Friday, 31 May 1991.

Vertical sca les

Saturday, June 1, 1991

-

Cond 0-SmS lcm

......... pH 0- 1'

---Temp 10.-.0 °C -

·-

Turb 0.1000 NTU

- - - D.O 0-10mg/l

,. " Figure 3 Sewer data from CSIRO Lowe,' Plenty site on a Saturday, 1June 1991.

Time , hr

sign ificant buffering of any discharges. A Mono 'Grifter ' pump-maceracor 6 was insralled on the surface, with an 80 mm PVC inlet pipe immersed in the weir. The 25 mm outlet was piped into a sire shed containing the field prototype and computer. The first trial was aborted when a mop head was sucked into the inlet, and fouled the maceracor. Consequently, a bell mouthed adapcor was fitted co the inlet pipe. This was directed downstream, to deflect large objects and reduce inlet velocity. This approach was successful, with the pump being able to then operate for several weelts before fouling .

Results. Typical results for the liquid phase showed frequent and large excursions 2 3 4 6, 7

Sensorex, CHK Engineering Pry Ltd .

Anal ite 156, McVan Instruments Pry Ltd .

Danfoss Australia Pry Ltd. Mono Pumps (Austral ia) Pry Ltd .

WATER FEBRUARY 1994

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Vertical sca les

I· ·I I ·I 1.

I I.

November 30, 1991

-Cond 0-10ms1cm .......... pH 0-1 4

- - - T,mp 10-4o 0c

- · -Turb 0-1000NTU - - - o .O: 0·I0mg(L

ii

/Y\

. · ·. . . . . . ./. . · · · f· ·IT:,,c:< . . . . f .v........... ,r

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v-; ----i, !

,-~"1 •. __ _

I iI .~ 1!l ii .,_.- · - · - - - - - - - - - t- 1;-j-.--7r,I- '"""-- ----.:::,r--- --

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Figure 4 Sewer data from CSIRO Clayton

site on 30 event.

ovember 1991 . ote large turbidity

Ve rtical scales December 8 , 199 1

-

COnd CH0mS /cm

· ······ PH 0-14

- - - T•mp 10-,o"C -

- - Turb 0-!000NTU

······!\················· ..... //······· ···················································· -~1\i~ ___ ___ __ /--- --------- - -- --

Jjl _,.- ·--- - -- - - -

------·--- -- -,a

12 Time, hr

21

,.

Figure 5 Sewer data from Brushy Creek on 8 December 1991 showing turbid event at abottt 1.30 a.m.

Ve rt ica l sca les M arch 30, 1992

-

Cond 0-lmS / c m ··· pH 0-14

- - -T,mp 10-• o 0c -

·-

Ti.ub 0.5000 NTU

1'

,1,iI

1, (\

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---- ...p .:- .--:=:~--""·-.

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12 Time, hr

Figure 6 Sewer dat~ f rom the Levanswell Rd site on 30 March I 992 showing regular hot water episodes. and acid discharge at about 7.30 Cl . Ill.

in most parameters, as opposed to the case at Lower Plenty. The Clayton sewer was fed by a small num be r of di sc hargers, so char their individual effects were noticeable. A recurrent extremely turbid event was found to be due to discharge of pumice wastes from an indusrrial cleaning process (Figure 4).

Brushy Creek treatment plant.

Me lbourne Water has a number of sma ll regional and neighbourhood sewage treatment planes throughout rhe metropoli tan area. The Brushy Creek plane in Croydon treats mainly dom estic waste, with only a small conr riburion from industry. Various sampling sires were tried around the plane before it was found char the portable Mono 'Grifrer' pump/maceraror could operate sarisWATER FEBRUARY 1994

factori ly from rhe V-norch weir feeding one of rhe treatment ranks . There were, however, problems with fo uling of the inlet, so it was necessa ry to install a coarse scree n filter which the plant operator cleaned regularly.

The parameter traces showed the typical diurnal pat tern associated with domestic activity, bur also signs of industrial activity were evident (Figure 5). Melbourne Water had been alerted char one of the few major industries in the area had been dumping its process ranks after-hours. Examination of the logged data showed a large turbid discharge every morning between 1-2 a.m. , com mencing December 8, 199 1 (apparently the leadup to Christmas is an ideal rime for some industria l housekeep ing). Th ese resu lts enabled Melbourne Water to confront rhe offender and stop the illegal discharge.

The tr ial continued for 2 months , and demonstrated char raw sewage influent can be monitored continuo usly ar treatm ent plants, and char sign ificant discharges can be detected . However, the surface mounted pump was nor adequate for long term unattended use.

Levanswell Road, Moordialloc.

The sewer monitor was then relocated co a test sire in rhe busy indusrrial esrare of Levanswe ll Road, Moordiall oc . The sur face mounted pump was now replaced with a submersible ABS Piranha 17-30 pump1, which was located in a wee well fed by the main sewer lines, with the sensors and electronics situated ad jacentl y in a small on-sire caravan.

This configuration proved very reliable, and operated continuously for three months with no pump problems.

Results. After the first week of moniroring , several features became apparent (Figure 6). The temperature in rhe we e we ll was risi ng regularly by up ro 10°C above normal (the actual discharge wou ld be much hotter, considering dilurion and distance from rhe wet we ll). -Ir was eventually traced to discharges of hoc water from an indusrrial cleaning process. Melbourne Water regulates such discharges because they can ourgas substantial amounts of noxious vapours from the

sewage. A regular discharge of acid effluent (pH 2) was occurring around 7.30 a.m. every Monday, Tuesday and Wednesday. Thi s pH was low enough to damage the sewer pipes, and it was traced ro a metal finisher illegally dumpi ng acid wastes into the sewer.

Another regular fea ture was for opaque and highly coloured discharges to be evident for periods of more than an hour. The turbidiry could exceed 10 ,000 NIU (abo ut the same value as full strength mi lk 1) . Highly turbid discharges are often correlated with large amounts of solids, which are a significant facror in rhe cost of sewage treatment.

All of these ev.ents were totally unsuspected, and of considerable interest to Melbourne Water. However, characterisation of these discharges requires char samples be collected when an event is detected. The most practicable means to do chis would require insrallarion of an aurosampler, triggered by rhe data logger.

Hunter Water Corporation. The sewer mon ito r was th en tri al led ar the Hunter Water Corporation in Newcastle. Ir was installed for two months mon itoring sewage influent ro Burwood Beach and Edgeworth trearment plants, where ir performed flawlessly (chis si re is over 900 km from our laboratory in Melbourne, so no specialised attention was possible). Burwood Beach had been experiencing sporadic odour problems of unknown cause, bur results from this monito ring trial proviped a possib le answer.

There was found ro be a very large diurnal change in conductivity of sewage influent , with practically fresh water being received for several houi's during the middle of the day, and very saline water at night (Figure 7). Ir is suspected char a recent earthquake had fractured sewer pipes , lea ding to ingress of groundwater. These fluctuations in salinity are nor optimal for the digesror biomass, so ch ar its ab ility co metaboli se wastes efficien tly could be compromi sed. This aga in showed rhe value of on-line moniroring.

Mitcham Pan Depot. Melbourn e Water has several depots where domest ic septic rank wastes are discharged by commer-

Table 1 Rernlts for feptic tank sludges (domestic unless otherwise indicated) Load No 01 0l (after 10 mins) 04 07 08 ll 12 13

14' 15 16 17 18 19 20· 21'

2

Conductivi ty (mS/cm)

pH

4.07 3.8 2.0 2.7' 4. 1' l. 3 0.9 2.6 l.4 l.6' 2.2 2.1 l.8 l.9 005 0.05

2 7.2 7.3 167 7.6 7.4 6.6 7.0 6.7 58 67 7.0 7.3 6.4 67 7.8

Parameter value not yet at equ il ibrium Treatment plant settled sludge

.l 4

Temp

DO

(OC)

Turbidity (NTU)

(mg/L)

21.4 21.5 21.6 25 6 19.5 210 21.4 20.8 20.5 21.8 21.8 20.9 22.8 21.4 22 .8 23. 7

1900 1800 1500 !600 , 2100 1100 >2 100 2000 700 ,2 100 >2! 0 1500 1900 1500 450 550

0.8 0.7 3.4 5.2 ' 6.0' 35 2' 0.6 05 l.3 ' 0.6 l.6' 2.3' 0.4 4.0 4.4

Public coilet sludge Septic tank cleaned out only 6 months previously

19

rure and turbidity sensors had an indefinite with no fa ilures in over one year of lifetime, - - - T.mp 10-40°C use.

The pH ·eleccrode generally survived for - · ·-DO o-1• mgJ1_ abom 6 monrhs before replacement was necessary. Th e DO elec trod e lasted from 2-6 monch s, dependin g on th e narure of rh e was re stream.

Calibration. The conductivity and temperature se nso rs pe rfor med flawl ess ly for more than 6 monchs, with negligible calibration drift.

Turbidity sensor perform ance depe nd ed Tlme, hr on the waste scream, bur it generally required Figure 7 Characteristics of sewage influent at Burwood Beach, ewcastle on Tuesday, 10 Sep- an initi al bedding- in pe riod of 2-3 days, tember 1992. ote the large variations in conduc- when the fou ling build -up would stabilise.

The sensor could then be ca librated, and tivity. needed co be checked weekl y co ensure accurate results.

Vertical scales The DO elect rode slowly accu mulated 0.5mS lc m o.u in so lubl e sil ve r sulfi de deposits, and the membrane thi ckness was reduced gradually by abrasion from rhe flo wing stream. Thus .... high flow rate, high solids and high levels of hydrogen sulfide all increased the rare of DO \ _- -- ·se nso r dereri ora ri on. Th e DO elec trod e needed chec king weekly co see if recalibration was needed.

The pH electrode was found ro generall y Tlme, minutes drift abour 0. 2 pH units per monrh , and was Figure 8 Emtern S!ptics (AGJ-481, Ticket thus calibrated monthly.

Ir was poss ibl e ro monicor ca lib rati on 5808) d11ri ng discharge of domestic septic tank dri ft by obse rving se nsor readings on rh e sludge (9 February 1993). daily charrs. These generall y showed a particcial waste disposal co mpanies. Th ere is a ular diurnal pattern , so char at a certain tim e con cern that industrial wastes could be (usuall y lace at night) repeatable readings mixed wirh domesti c efflu ents, because rhe were observed. The need for recalibration same tankers can be used co dispose of both could then be determ ined by watching the types of wastes . Indu strial wastes are sub- drift in these valu es . In many cases, sm all jeered co pre-treatment and analysis before calibration errors were nor significant if large they can be discharged co sewer, whe reas discharge evencs were the im porranc observadomestic waste is pumped co a holding pit nons. and then released inco the sewer with no Sampling Pumps. After the initial trials treatment or cesnng. with the surface-mounced pump-mace rarors, The sewer monicor was used for checking the solution was found ro be the submersible cankers as they discharged septic tank sludges pump (the ABS Piranha) wh ich has an ingeat the Melbourne War,er Mitcham pan depot. niou s se lf- cleanin g mutratin g impell er The trial was successful , and esrabl ished a design. This pump was found to fun ction means of monicoring discharges reliably from flawless ly fo r several monch s of continuou s ·septic waste tankers during rhe few minutes operation in all sewer locati ons reseed, unafof their discharge. It was possible co readi ly fected by gravel, or paper and plastic objects. detect if the pH were ourside the allowable limit, and rhe parameter "fingerprint" can be Conclusions The sewer monitoring sysrem has been used to confirm the source and suirabiliry for refi ned successful ly during more rhan 2 years disposal of each load (Figure 8).

Results. Twenty one ranker loads were ex tensive resea rch and development. It has res eed , and selected results are shown in been demon strated success fully in a wid e Table 1. The septi c sludges generally showed range of locati ons, including raw sewage in only small variations in pH and cemperarure, dom esti c and industrial sewers, influ ent at bur varied widely in DO, conductivity and treatmenc planes, and at septic pan di sposal rurbidity. This is nor surprising, as rurbidiry cenrres. Irs success has been due ro rhe fl owis ·a function of the suspended so lid s level , through des ign, the reliability of all of irs DO depend s oo th e prese nce of organi c componencs, and rhe fac t rhat very useful matter and the level of biological ac tivit y, inform ation was obta ined from monitoring and conductiv ity is related co the amounr of simple physico-chemical parameters. Ir provides concinuous surveill ance, being able ro dissolved solids. operate reliably for several monrhs with littl e Equipment attention , and is operable by non- techni ca l Sensor performance. pe r onnel. It can eas il y be tran sported to Reliability. The co ndu ctivity, tempera- various locations, and requ ire no consumabl es Vertical scales

September 10, 1992

-Co11a 0·5mS/cm

· ······ PH O·U

-

12

Feb1uary 9. 1993

. -Tu rb 0-5000 NTU

15

-

Cona

.... pH

- - - T..-np \(M.O•C -

·-

TVID0-3000NTU

- · - - D O 0- 1Smg1L

\

"

20

------ ~--

except mains po"'4;r and water. Mainrenance is straightforward , with sensor replacement only raking a few minutes. The sewer monicor also provides an excellent platform for incorporating specific sensors at a lacer dare.

The dara collected can be used ro characteri se sewage, and showed vari ati ons which co rrelated with expec ted pa ttern s of di scharges . Thi s in fo rmation forms a valuable data-base whi ch assists in sewer catchment managemenr , enables discharge evenrs to be idencified, and helps ro ensure chat offenders are detected. Th e system has co nsiderab le potential as a cosc-effective means ro protect sewer workers, rhe sewer fa bri c, trea tment planrs and the environmenr.

It can also be used as a mobile inspection unit for investigating suspect effluenrs, and some systems may be permanencl y arrached to the discharge poinrs of problem indusrries.

It has appli ca tion s as a di sc harge li ce nce enforcemenc rool, and makes more effective use of rrade waste officers.

It also offers a means of esrim aring di scharge loads of particular indusrries , by using an appropriate effluent metering algorithm (eg correlating turbidit y wirh suspe nded solids). Thi s would enable sewage rrearment authorities to more accurately assess and levy trade waste charges.

The sewer monicoring system could also be co nn ec ted to an autosa mpler, enablin g spec ifi e sa mples to be collec ted wh en an unu sual evenc otc urs, so th at sa mples are more likely to reflec t a rea l problem. Thi s 'intellige nt ' event-trigge red aurosampl ing wou ld be,.more effective rhan random or fi xed schedule sampling.

Acknowledgments Th e authors th ank th e Urb an Water Research Association of Australia (UWRAA) and Melbourne Warer who provid ed partial fundin g fo r th e pro jec t. We also th ank MACE Pry led for rh eir permi ss ion co publi sh chis paper. The early part of rh is work is published in UWRAA Resea rch Report o. 50.

References Albrecht.DR (1988), Ruhr R, ver Polluti on: 1988- Pol icy.

Economr. Management . and Appropriate Technolog)'· Proceedings of a Symposium , 27 1-28 1. American Water Resources Association, Bethesda, Maryland .

Bridge r, J ; CS IRO Di visio n of Chemicals and Polrme rs (199 1), Personal comm unicarion.

Bridger, J ; Pilkington.N H: Raper. WGC (199.l), Flow· Proporc ional Operation of Sewage Treatment Pilot Plants: Why and How. Proc. A\'I/WI A I 5th Federal Convention:

o- -81.l.

Briggs, R; Grat ta n, KT V ( 1990). Instr umentation and Control in the K W/arer Industry: A Review. Proceedings of th e 5th IAW/ PR C work shop, Yokohama and Kyoto. Japan, 1990, 2i-l,8. Perga mon Press, New York.

Bu ttz, J : Daigger. G ( 1990). Rea l-T, me B,olog,ca l Process Oprim izauon Using On-Line Monitoring. Proceedmgs of the 5th IAWPRC Work shop. Yokohama and Kyoto.

Japan. 1990 . .\4.\-.l 9. Pergamon Press. New York.

Dreicer, M: Care.) L: Rueppel. D W: ll untziner. CJ: Gonzalez, MA (1982). On- Line Liquid-Efn uenr Monitoring of Se wage ,u Lawrence Li ve rmore National Labo rato ry, National Technical lnformarion Sm ·ice, Springfield.VA. 2216 1. Report No. UCR L-884 25.

Firth B K; Cieslek, P R (1990), Biosensing for the Protection of\XlarerQuality, TappijounMI, 73, 91-95 .

Hanson, CA (1981), Dara Acquisition for River Management, \Vnte.- Science <11u/Tech11ology, .13, 687-692.

Hey. A E (1980), Continuous Monitoring for Sewage Treatment Purposes, \Valer Pollution Co11trnl, 79, 477-484.

Jolley, R L; Rivera, A L (1988), Continuous Monitoring , Automated Analysis, and Sampling Procedures, j\11/CPF.

60, 799-801.

Jolley, R L; Rivera, A L (I 989), Continuous Monitoring, Automated Analj•sis, and Sampling Procedures,JW'CPF,

61, -82-785.

Kohonen, T (1985), Availability of Automatic \Xlacec Quality Monitoring for Finnish \Xlacercourses, 1 ational Board of \Xlaters, Finland . \Xlater Research Institute Publication, No 62, 3- 19.

Kugelman, I J : Houthoofd, J ; Schuk, \XI (1982). Operarion and Maintenance of \Xlastewater Sysrems Inc luding lnstrumencacion and Automation, j\11/PCF, 54, 642-646.

Nanbo, K; Kunogi, R (1981), Continuous \Xlater Quality Monitoring System Using Telemetry in the City of Osaka, \Va/e,- Science a11d1'ech11ology, 13, 639-644.

Pitt,\'(/\'(/ Jr; Demon, MS (1982), Continuous Monitoring, Automated Analysis, and Sampling Procedures, j\11/PCF. 54 , 576-583.

Rogalla, F; Roudon, G; Ravarini , P; Bourdon, F (I 990), Continuous Follow-Up of Aerated Granular Biofilre rs with On- Line Sensors, Proceedings of the Sch IA \XIPRC \Xlorkshop, Yokohama and Kyoto, Japan, 1990, 89-96.

Pergamon Press, New York.

Schafer, J; Schumann , H; 1iemi tz, \V/; \V/iesmann, U (I 981), Evaluation of \V/ater Qualiry Dara Received by Automatic Control Stations at the Teltow-Canal in Berlin (\V/esc), Water Science and Tech110/ogy, 13, 663-670.

Stephenson, J P; Luxon, E G; Monaghan, B A; Gillespie, R G (1981), Evaluation of Instruments for Continuous Activated Sludge Moni toring. Water Sciwce and Tech110logy, 13, 721-728.

Sweeney, M \V/ (1991), Instrumentation and Automation, Res. j\YIPCF, 63, 424-425 Tieman, A; \Xlagner, B (198 1), Development and Use of a Continuous TOC -Measurement Device in \Xlasrewater Purification, \Vate,· Science a11d Tech11ology, 13, 211 -

216.

Vanderborght, J-P; \V/ollasr, P (1990), Continuous Monitoring of \V/asrewarer Composition in Sewers and Stormwacer Overfl ows, \\1/ate.- Scie11re and Terlmology, 22,

271-275. \V/hirby, F J ; Cottrell , DR ; L1u, D C-\V/; Bishop, E (1983), Evaluation of a Sampler fo r Liquid Effluents, \Valer Research, 17, 1491-1498. \Xiong , \XI K; Smith , D \XI (1992), Evaluation of an On-Line Specific Oxygen Uptake Race Monitoring Apparatus at the Gold Bar \V/astewarer Treatment Plant, E11viro11111w 1t,I Technology (Letters), 13, 45-54.

BOOKS An Introduction to Project Evaluation Malcolm Hollick, Longman Cheshire, 1993, ISBN O 582 87579 3, 261 pp in 7

chapters, This book is intended to serve as a rexr for final year students in ci vii engineering, or as a guide for pracri rion ers who need ro appreciate rhe range of avai lable evaluation techniques better. The chapters cover: introduction to aspects of decision making; cosrbenefir analysis; extended CBA (intangibles, externalities and equity); dealing with uncertainty; alternatives ro Cl3A (ie planning ba lance sheets and quali ta tive methods); statutory eval uation processes; and publ ic involvement.

Hollick has a relaxed but critical style of writing and deftly conveys rhe srrengrhs and wea knesses of all the techniques cove red.

Throughout the boo k, worked exam pies illustrate the methods as well as throwing up anomalies to demonstrate che pitfall s.

The inclusion of a chapter on public partici parion is most welcome, sin ce it is in there rhar many projects have faltered . Suggestions go as far as ind icating searing plans conducive to non-threatening communication at meetings.

Although, as the author warns, rhe depth of coverage is not sufficient to make an expert of rhe reader, it wou ld be inval uable for anyone wishing to appreciate (and to be suitably cynical about) rhe evaluation techniques applied by 'experts'.

Hollick wrote from a Perth base and rhe examples he quotes are all Australian, includ ing several relating to water. Thar , coupled with che coverage of Austra lian statutory processes, makes rhe book all che more relevan r to local readers.

C Davis

Wastewater Management in Coastal Areas

Editors:J Bontoux and J Bebin. Per! man Press. ISBN 0080421911 . 300 pag Cost: £70 This book (Water Science and Technolo 25, (12), 1992) reports rhe IAW PF Specialised Conference, France, Apri l 19 and comprises rhirry rwo papers togetlwirh a summary and conclus ions by o of rhe editors.

The authors of rhe paper concentrated achieving water quality that presented lit risk to rhe environment or ro people, whed from sewage and ind ustrial wastewater from contaminated stormwarer. Some pap< stressed the need for env ironmental imp, studies and mathe matical mode lli ng ensure wastewater management options Wf fu ll y investigated . A number of amhc described marine di sposal of waste wi appropriate rrearment, including a range disinfection methods. The im portan ce diffuse poll ut ion and the imporrance of cc lection storage and treatment of stormwar were discussed. While a number of papf concentrated on marine discharge for coast towns , other solutions such as agricu lrur use, rourist tjevelopments such as golf cours and groundwater disposa l ro combat sa intrusion were seen as valid solutions.

The conference appeared ro come up wi two•approaches, first a river basin manag ment approach ro control eurrophicarion ar second if management of wastewater is be effective, it must be carried our on global basis.

The conference concluded rhar we ha• the rools necessary for management bur mo research and experimentation is necessary.

Frank Bish(

Authors Dr Roger O' Halloran is a Principal Research Scientist in the CSIR O Division of Materials Science and Technology. He gained his PhD in electrochemistry, and worked in marine environmental analysis with the Department of Defence, as Principal Chemist with the EPA (Vic), then with Melbourne \\1/ater, before joining CSIROin 1990 to work on this project.

Dr Brett Sexton gained his PhD in s111face science, and initially worked for General Motors in USA , before joining CSIRO to w01·k on smface analysis techniques. He is a Project Leader in the same Division.

Mr Norman Pilkington is a Principal Research Scientist in the Water and Wastewater Technology Program of the Division of Chemicals and Polymers. He commenced working in 1973 on water reclamation from sewage, and has since worked on projects mch as disinfection by-prod11cts and ion exchange, his partimlar expertise being in analytical t1Spects.

WATER FEBRUARY 1994

Apology In the report on the BOOT semi nar, page 39/40 of the December issue, Figure l was inadvertently omitted. The missing fig ure is reprod uced below, and describes rhe complex linkages between the parries involved in rhe contract for the Yan Yean Water Treatment Plant.

MELBOURNE WA TE R C ORPORATION ICUSTOMERl

_____

NORTH WE ST WATE R A US T RALIA PTY. L TO. !OPER A. TO RI

._

YAN YE AN WA T ER PTY. LTD. I OWNERI

__. ' ' \ '

NORTH WES T WAT ER INTE RN AT IONA L LTD.

!PROCESS DESIGNER)

CONTR AC T

''

REVIE W

''

\ -------

DES IGNE R CAMP SCOTT FUR PHY P TY. LTD. !CON SUL TING ENGINEER S)

T RA N SF IELO CONST RUC TI ON PTY. L TO. ITURNICEY CONT RACTORI

SUB CONT RACTORS ANO SUPPLIERS

T RANSFIELD C ON S TRUC TION SITE

YAN YEAN WATER TRE ATMENT PLANT PROJECT ORGANISATION CHART

2

MANAGEMENT

COASTAL EUTROPHICATION: PREVENTION IS BETTER THAN CURE THE PERTH COASTAL WATER STUDY ~

DA Lord* Abstract Growing populations imply increasing requirements for the provision of potable water and for the disposal of created wastewater. The Water Authori ty of Western Australia (the Authority) has the responsibi li ty for providing these services to metropolitan Perch, where flows of treated wastewater are anticipated to increase at a rare of about 3% per year up until the year 2040.

At present, virt ually all of the created wastewater from Perth is discharged to sea through well designed marine outfalls from three locarions. Regu lar moniroring has shown char beaches are always wit hin the most stringent health criteria, whi le sed iments and marine organisms are free from elevated levels of heavy merals or rrace organic compounds. Nutrient enrichment of coastal waters is the main concern with any future increases in discharges of crea ted wastewater.

The Authority is presently preparing a strategy for the disposal of created wasrewarer for the next 50 years . This programme Wastewater 2040 - includes comprehensive community consultation, detai led evaluations of alternative (land) disposal options, and a thorough study of the influences of present discharges to sea as well as a forecast of the effects of increases in discharges of created wastewater co sea. This latter study is the Perth Coastal Waters Study (PCWS).

Perch 's coastal waters are shallow, clear, moderate energy, and of low productivity.

Nitrogen is considered to be the li mit ing nutrient in these waters. An integrated ecological model COASEC (Coastal Ecology) is be-ing deve loped to represent the main marine process of interest with regard to nutrient enrichment. In COASEC, physical processes are bei ng represented by a 2dimensional 2-layer barocropic hydrodynamic model. Concentrations of chemicals in the water column are determined using advecrion/dispersion relationships, while the main bio log ical processes bein g depicted are 22

primary production, light attenuation, and nutrient recycling.

Models provide an invaluable aid for the rational observation of complex environments. Ecological models oversimplify conditions, and forecas ts are seldom sufficiently precise for use in management. Well designed monitoring programmes are necessary to meet chat objective.

Introduction The Water Authority of Western Australia (the Authority) has the responsibility for providing potable water and treating wastewater in Western Australia. For Perch, the Authority operates a sewage collection and treatment system based on three major wastewater treatment plants (WWTP 's) which discharge created wastewater to sea via submarine outlets (Figure 1). Traditionally there are three main concerns associated with wastewater discharge to sea. These are: microbiologica l quality of bathing waters; accumu lation of heavy metals and organic compounds in sed iments and marine animals; and, enhanced primary prod uction as a result of nutrient enrichment.

Microbiological quality. Barbing water quality is normally assessed using bacterial indicators such as faecal co liform, and in Australi a is evaluated against NHMRC cri teria ( HMRC, 1990). Summarised values for Perth's popular northern bathing beaches are shown in Table 1, where it is clear that bathing waters are always well within acceptab le criteria. Cr iteria for bathing water in Australia are comparable with international levels, although they are not the most srringent. This honour belongs to Hong Kong, where a seasonal log mean E. coli of less than 24 is needed to ach ieve an A raring, which equates to a risk factor of0 per 1000 of population for gasrro-intesrinal infection (Cheung et al, 1991).

However, only 9 our of 42 of Hong · Kong's beaches meet chis high standard , whereas all of Perth's bathing beaches meet

the Hong Kong A criteria. Clearly, what is more important is nor necessari ly the level at which criteria are sec, bur the actual levels that are ach ieved .

Persistent contaminants (heavy metals and persistent organic compounds) . Surveys for persistent contam i-

nants (heavy metals and persistent organic compounds) have been conducted in the vicinity of the outlets, and include measurements on sediment and biota (lobster, abalone , filter fe€'ding runi cares , and mussels). The most recent of these were conducted at Ocean Reef in 1991 (BBG, 1992) and Cape Peron in 1992 (HGM, 1992).

The resuTrs of these rwo studies both indicated no significant (statistically speaking) elevation of heavy meta ls or pe rsistent organic compounds in either sediment or biota, wh ile all of the biota samples contained levels which were well within food standards (WA Food Regs, 1987). These results are nor surprising as only a small component (approximately 10%) of the flow to WWTP's in Perth is from indusrrial sources, and these have to meet stringent crireria before being accepted into the sewer sys rem.

Within the Perth Coastal Waters, rhe only significant case of heavy metal contamination has occurred with rri-buryl tin (TBT).

Regional sediment surveys have identified a number of·sires with elevated TBT levels (EPA, 1993). These are close to harbour areas south of Fremantle and along the east side of.

Cockburn Sound , as well as in Thompsons Bay, Rottnesr Island. Elevated TBT levels are associated with the use ofTBT in antifouling paints. The use of TBT-concaining paints in Western Austra lia has been prohibited on boars with hulls under 25m in length. Boars over 25m are allowed fo use low leaching forms of this paint, while internationa l vessels are outside local jurisdiction.

*D A lord Associates WATER FEBRUARY 1994

Nutri eots, eutrophication, an c the conce pt of lim iting nutrient

SOUT H WE ST W ESTEAN AUSTR ALIA

~"'"~/

I I

8/BEAC H

i i

O c ean Ree1

i i

I ~ ! ', I

', 1·-~ ., .

1

IND/A N OCEAN

Ocean Reef Ocean Ou clets B 1820 195 10 85 ni l 85

A

Overall length (m) Diffuser length (m) Di ffuser depth (m) Exisring capaciry 1990 fl ow (ML/d) 2040 fl ow (ML/d)

1620 195 10 65 57 65

Effl uent qual ity (mg/I) NO3- N NH3 -N PO4- P TSS BOD

Swanbourne Ocean Ouclet A 1000 91 II

100 50 65

Cape Peron Ou clet A 4100 324 20 125 84 250

27 2 10 25 5

37 10 13 II

11 0 180

Secondary (acrivared sludge) from Beenyup

Secondary (anivared sludge) from Beenyup

Primary from \Xlood mans Point and Cape Peron

>l ll

Trearmenr

Figu re 1 Perth coastal waters showing ocean 011tlets and bathing beaches WATER FEBRUARY 1994

Incidences of nurrient enrichment causin! environmental degradation in coastal area: are numerous. The most celebrated of these include Chesapeake Bay, Tokyo Harbour, anc the northern Adriatic, wirh examples frorr Western Australia bein g Prin cess Roya Harbour, the Peel- Harvey estuary, and Cock burn Sound (Walker and McComb, 1992).

Marin e and es ruarine sysrems arounc southern Ausrral'i a would have been olig atrophic (low in nutrients) before huma, impacts, and consequently, are particular!: susceptible· to an additi onal injection o nutri ents. utrient enrichment stimulates plant algal producriviry, lead ing ro a build-up o organic matter in rhe water column and sedi ment, wirh ultimate reductions in dissolve, oxygen in rhe warer body following decom posi rion of this organic mareri al. Orhe earlier manifestations of nurrient enrichmen ma y include reduced diversity, shifts i1 species composition particularly in the phy roplankton , increased phytoplankton bloom1 especially of toxic species, increased macroal gal biomass , loss of seagrasses, a shift fron filter feeders to deposit feeders, and in sever cases, increased disease in larger invenebrare and verrebrates (eg. fish and crabs) (Nixon 1993). The nutrients of most concern ar th erefo re those which Stirn ular e plan growth , usually rhe "macro-nutrients", nirro ge n, phosphorus and somet imes sil ico and/or iron.

In general, freshwater sysrems are phos phort!s-limired while temperate open marin syst ems are nitroge n-li mited. Tropica mar in e sys rems are often phosphorus · limited , due to removal of phosphorus b adsorption onto carbonate sediments. Th dilemma is furrher increased by recognisin, rhat there may be seasonal changes in limit ing nutrient ac any sire. This is particular! true for phytoplankton comm unities , wher for example, the phytoplankton could var from diaroms (ultim atel y silicon limited: through to dinoflagellaces (nitrogen or phm phorus limited), to blue green algae whic can fix atmospheric nitrogen and are thert fore phosphorus limited.

Ic is se ldom that only one nutri ent i always lim iting in a water body. Howeve nitrogen is normally implicated in the limi ration of macrophyte producriviry in olig atrophic waters of low phytop lankto content , and is the nutrient of attention i the Perth Coastal Waters Study. This decisio was made based on the known oligotrophi starus of Perth Coastal Waters, plus the N/ ratios in treated wastewater of 6.6 - 11.4/i which are far lower that the Redfield rati which indicates rhat the relative requirt ments of nitrogen and phosphoru s fc primary production is 16/1. It is therefo, valid ro identity nitrogen as rhe limirin nutrient in oligotrophic marine system: with an awareness that phosphorus may !:

Table 1 Microbiological Q11ality of Perth's Northern Bathing Beaches 1963-1993 FAECAL COLIFORMS PER l00ML l 962/63 (N =54) AN UAL % % MEDIA 1 >150 >500 Port Beach Cottesloe Swanbourne City Beach Scarborough Sorrento Mullaloo Ocean Reef Burns Beach

4 9 9

2

0 5

1972/73 (N =74) At UAL % % MEDIA , 150 >5 00 4 15 7 4 9

0 0

8 11 0 0 4

0 4 0 0 3

1982183 (N=55) ANNUAL % % MEDIAN >150 >500 0 6

0

0 4 2 4 2 4

0

2

0 2

2 2 2 0 0 0

l 992/93( =20) A 11 UAL % % MEDIA1 >150 >500 2 20 0 2 0 0 0 0 0 0 0 0 0 0 5 5 5 2 16 5

Note: Australian criteria for primary contact waters are: Median of fueca l coliform levels not to exceed 150/100ml in a minimum of five samples taken at intervals of no less than one month . 80% of samples to be less than 600 per 100ml (NHMRC, 1990).

Table 2a Total Loads of Nitl'Ogen (Dissolved Inorganic) from Land Based Sources to Sea . SOURCE Groundwater Industry Treated wastewater Surface drainage Atmosphere Rivers/estuaries TOTALS

TONNES 290 1l62 l035 l9 85 l071 3663

1979 % OF TOTAL 7.9

3l.7 28.3 0.5 2.3 29.2 l00.0

Table 2b Nitrogen Loads from Ocean Exchange

TONNES 445 638 2974 32 l44 l270 ;930

1990 % OF TOTAL 8.1 l l.6 54.0 0.5 2.6 23.0 l00.0

2040 TONNES % OF TOTAL 396 4.5 7920 42 20 l l500 l0033

3.9 <l.0 78.9 0.5 2.0 l4.9 lO0.0

the future loads of nitrogen chat can be discharged co these coastal waters and retain l. Perth Coastal \'(/aters (lOkm x l50km x lOm) acceptable environmental values. Further, as Volume: l.5 x lO"m' one of the discharges enters the Marmion Exchange rate/turnover time: 20 days Marine Park, only minimal environmental (ie. l8 times per year) disturbance is considered acceptable.

Total nitrogen concentration (TN) 200 µg /1 Nitrogen enters the coastal waters from a Total dissolved inorganic nitrogen concentration (TDIN): l0 µg /1 number of sources, including industrial dis2. itrogen from ocean exchange charges, drains, groundwater, rivers and estuT : 52.5 x 10' tpa aries, ocean exchange, deposition from the TDIN: 2.6 x l0' tpa air, and created wastewa ter. Ar present, 3. itrogen from terrestrial sources wastewater contributes about half of the total TN = TDIN: l990 - 6 x l0' tpa load of dissolved inorganic nitrogen (DIN) TN = TDIN: 2040 - 10 x 10' tpa from terrestrial sources to coastal waters; this important under particular cond itions, such proportion will increase with rime (Table 2a and 26). as water column anoxia.

A comparison of nitrogen loads from land Wastewater 2040 based discharges with chose from oceanexPerch's population is expected to increase change, (Table 26), shows chat DIN loads to about 2.6 million by the year 2040, with from land can elevate local ocean concentraconcurrent increases of treated wascewace'r tions (ie up to 2km) but provide a small fracflows from 220Ml per day (1993) to 600ML tion of the total ni rrogen load to the area.

Models for determining eutroper day (2040), (Figure 2). To meet chis demand the Authority has embarked on a phication of marine systems. The sysprogramme to produce a wastewater disposal tematic exam in ation of eurrophicari on of strategy chat is environmencall y, socially and aquatic systems has ranged from the use of economically acceptable to the community, empirical relationships to the implementation of detailed determini st ic ecologica l and is called Wastewater 2040.

The Wastewater 2040 programme has models.

Empirical models. Empirical models have three main components: • Community information and consultation en joyed wide use in freshwater systems, where cause (n utri ent loading) and effect programme. (e urroph icarion) have been successfu ll y • Perth Coastal Waters Study. related. The best known of these links phos• Alternative effluent disposal options. phorus loading into lakes to their eurrophicaPerth Coastal Waters Study. cion status (Vo ll enweider, 1976). These Determination of acceptable nutri- relationships have been used to develop manent loading rates. Nitrogen loads to agement strategies wh ich are relatively Perth Coastal Waters. The principal objec- scraighcforward, with load reduction usually tive of the PCWS is to examine in detail the being required where eutrophicarion is occurhistorical and present influences of nutri ent ring, or may occur.

Similar empirical relationships have been discharges to sea off Perch, and to determine 24

applied ro various ma!iine systems but with less success, for a number of reasons. First, marine systems cannot as easily be described as being only nitrogen - or phosphorus limited (sometimes a system will display both characteristics) and second, the far more variable and complex hydrodynamics of marine systems mean char a single estimate for flushing or water exchange is nor representative.

Consequently, a marine system may oscillate between trophic states as a result of variations in physical conditions. onecheless, some useful yardsticks have been deve loped for evaluating the "potential" for coastal eucrophicacion based on nutrient load. For example, J aworsk i (1981) suggested a relationship based on annual loading rares char showed char eucrophi cacion would not occur with loads less than 5.4g N/m2/a for nitrogen limited systems, and 0. 75g P/m2/a for phosphorus limited systems. The shortcoming of Jaworski 's system is the lack of incorporation of a facror co cake account of flushing , or water exchange. A simi lar application of empirical loading rares of nitrogen as a function of water exchange has been usefully applied to evaluate the potential for eucrophicacion for sires proposed for mariculture in Hong Kong. (Broom et al, 1991). This relationship included a geographic facror co cater for che distance from the sire of concern to the open boundary where water exchange occurs.

Applying similar considerations ro Perth's coastal waters, existing, and potential future nitrogen loads were calculated (Table 3) and assessed with regard to thei r likelihood of eli citing eurro; hi carion. For chi s purpose, comparative daca from Cockburn Sound were used , where it has been forecast that seagrasses would be unaffected by nitrogen loads of 500kg per day (Pearce, 1991 ) bur rim eurrophicacion effects may commence at , loads of as low as 1000kg per day. For Cockburn Sound, chis translates co nitrogen loads of 125mg N per m2 per flush and 250mg N per m2 per flu sh respectively.

Applying this simple criterion to che areas co which Perth's outfalls discharge, it is concluded char nitrogen mediated eurrophicarion is: • unlikely in che Whirfords lagoon which contains part of the Marmion Marine Pack in the foreseeable future , • most unlikely in the vicinity of the outlet of the Swanbourne outfall, • possible in che vicinity of the Cape Peron outfall after the year 2000.

Simple empirica l re lationships of this kind provide a rapid indication of the possible consequences of nutrient loading.

However, they may not be valid when considering the effects of an increase in loading, as cause/effect relationships are seldom linear.

Under these conditions a more dececminiscic ecological model is required. These models require extensive field measurements for validation and calib ration of the physical and chemical components , and field as well as laboratory studies for examining effects of WATER FEBRUARY 1994

increased loads. The Au choricy has elecced ro develop such a de rail ed eco logica l model which is called COASEC ro supporc ics developm enr of wasce wace r di sposal scracegies (l ord , 1993).

The COASEC Model Model description. An inregra ced

Table 3 Nitrogen Loads to Coastal Waters 1990 and 2040 LOCATIO

\'(lh irfords Lagoon (Ocean Reef Outler) Gage Road - Trigg ls (Swanbourne Outler) Sepia Depression I (Cape Peron Outler) Cockburn Sound

DIME S!ONS LXW! N km D! N m

FLUS H! G TIME DAYS

JO x 5 IO I 5x(6-1 5) 15 5X 5 20 l7 X 7 20

l -2 (2) approx 3 (3)

NITROGEN LOAD! G TPA g/m7a mg/m7flu sh 613 (1642] 860 (11 18] 1350 (3166} 1095 (180]

13.072 33.0 11.7 15.2 18.0 42.0 92 1.4

COMME TS

WQC mer. No evidence of 177

eutrophicarion.

96

WQC mer.

126 197 462 766 125

eurroph icarion.

1

o evidence of

WQC mer. No evidence of 2-4 ecological model is being prepared ro repre(4) eurrophicarion . sent che phys ical, chemica l, and bio log ica l Loss of seagrass.

10-60 processes ch ar ace domi nanr in che coascal (30) Estimated safe level fo r seagrass. wacers off Perch , and is k nown as che Possi ble localised esr 50-350 688 1950km' 7500 3.8 COASEC (Coascal Ecology) model. Prorocype Parr Phillip Bay eutrophicarion. (l00) Melbourne 13 model development has conceocraced on the l ocalised eu trophicarion.

450km' 51 2200 462.0 6800 Naraganserr Bay USA Ocean Reef area.

5 Physical processes. Ph ys ical processes in Tokyo Harbour Localised eucrophicarion.

40 12 00 1400km' 89.0 9770 35 che mode l are rep rese nted by a cwo- laye r barocropic model (Backhaus, 1985). Reg ional Noce l: For each location 1990 loads are presented. \'(/here available anricipated 2040 loads are shown in square brackets. circulaci oo paccero s are co ncroll ed largely Nore 2: Values for basin dimensions and flushing rimes for \'(lesrern Australian waters from van Senden 0991). Flushing rime by che l ee uwin Curreor and wind stress used fo r load calculations in round brackets. and influenced by local ropography. Simulaced sur face flo w pacce rn s fo e a reg ion Table 4 1 11trients off Ocean Reef Outlet approx im acely 15 0k m (norch -s our h) by I000+ m BACKGROUND D!FF SER 250m i00m 50km (ease- wesr), (Fi gure 3) show rhe domi10-20 80- 100 20-.l0 <10 30--40 oaoc southward flow of offs hore waters (ie NH3 µg /1 10-50 15-200 40-50 15-50 30-60 TIN[tg/1 greater than 20m) regardles of wind direc10-20 7- 15 20-30 PO4 µg/1 70--80 50- 70 tion, as well as an ed dy south of Rocrn est Island und er most conditi ons (Pattiaratchi Table 5 Biomass of Pri111a1y Producers in Perth Coastal Waters and Backhaus, 1992).

Hydrodynamic models are also being preBIOMA SS: MEA A 10 STA NDARD DEVIATION g dry wt m·' pared for rhe imm edi ate vicin ity of each of HA BITAT \'(I i 1TER AUTU MN CATEGORY SPR ING SUM MER the outfa lls using a 25 0m x 25 0m grid . For Seagrass th e Ocea n Reef area rhe mode l domain 250 (50) 375 (75) Seagrass 3.l0 (130) 500 (100) - Posidonia 2 (2) 100(100) 25 (25) 5S.(55) Epiphytes ex tends 10km (norch- ouch) by 5km (easr700 (140) 600 (120) 420 (170) 800 (160) - Amphibolis Seagrass wesr). Ac present, rhe reg ional model and che 180 (180) Epiphytes (roral) 410 (230) 600 (600) 350 (350) local models are nor nested, and are run inde4 (4) 2 (I) 6(6) 2 (2) Epiphytes (leaves) pendently. The rime seep for chis application Reef 600 (600) 1200 (1200) Kelp (Ecklonia) 200 ( 130) 1800 (1800).

(700) 0 (1000) 700 Kelp (Sargassum) of che local model is 1 hour.

Pavemenr nm presenr l000 600 (600) 160 (90) 1800 (1800) 1200 (1200) Wind srress for mode l co mpurari on is Coastal platform Kelp (Eck Ionia) provi ded by a simulaced wind fie ld , using real wind informacion from Ocean Reef, Fre- ocher materials assumed co behave conserva- l agoon ro rw ice bac kground levels up co manc le, and Rocrnesr Island. Dara fo r Ror- tively and co have no cransporr between cells. 2km from rh e diffuse r. Summa ry medi an rnesr Island are rhen reprodu ced anoch er Sources, such as groundwacer, ouc fa ll s, or values for nucrients in surface sampl es fo r che 20km fur ther norch co provid e a simulaced nmriencs from reminerali sacion processes in period 198 1-1 99 1 are shown in Tabl e 4 offshore reference sire. rhe seclim enr are in clud ed in app ropri ate (Kinhill , 1991).

Model ca lib racion makes use large ly of cells.

Ir is kn own rh ar rh e plum e from ch e The rim e seep for rhe calculation of con- Ocean Reef oucler is scill buoyant upon surcurrenc merer reco rd s. For ch e summ er period , flow s in rhe \Xfhirfords l agoon area cencracion fi eld s is rhe same as for the hydro- fac ing and full mixing of rhe warer column are large ly wind driven; correlati on during dynamic segmem, namely, 1 hour. onl y occurs ar some distance from rhe oucler, rh e wi nrer pe ri od is less significa nr , wirh Water quality. Plum e charac reri sri cs ch is dista nce bei ng very depende nt on rhe winds being li ghter and more vari able in and warer quali cy derails which are used for degree of scracificari on in rhe wacer column. model valiclari on are obtained from a combiA rheoreri ca l an alys is (Pacciararchi and direction .

Res idence rim e of wacer wichin che \Xfhic- nation of physical (CTD) and chemical mea- Imberge r, 1991) of che effluent plum e indiford s l agoo n area, whi ch is defin ed as an sure ments. Surv eys co nfirm a number of caces char after che plu me reaches the surface, envelope 10km long by 5km wide, is esc i- feamres of rhe area, such as: ic will be loca ted ar a depth of lm . Th e maced as usuall y less chan cwo clays, wirh che • inshore waters are cooler/lowe r salinity in plum e subseq uenrl y undergoes a hydraulic main exchange mechani sm being .cross shelf winter, and warmer/higher sa linity in jum p and is mi xed ro a depth of 3m. Field exchange, as well as wind-d riven along-shore smclies have confirm ed chis behaviour (ibid) . summer, • bac kground sra ri c nurrient and chloro- Full verc ical mixing of rhe plume can occur cransporc.

Transport and advection/disperph yll levels vary subscanti all y. Summer within 05- 1.0km (from fi eld results, wirh sion. The concencraci on of chemical maceri valu es are usua ll y lowe r rh an wint er strong wind induced mixing) or up ro 12km als in the wacer column is represented using a levels, and (theorerical value, wich no wind mi xing and cransporc expression char considers di ffusion • rhe plume from rhe Ocean Reef omler is onl y vertical cli ffusion)(ibfd). (horizontal and verci cal) as well as loss or gain srill buoyanc ar che surface.

The fu ll mixing of rhe plu me is an imporof material uch as che setcling of particulaces Th e routin e wace r qu ali cy programm e ta nt consideration in eva lua ting ecological or the reminerali sati on of organic materi al. char has been undertaken by the Aurhoriry in effeccs on beochic planes, as chei r response is Ac present, dissolved inorganic nicrogen, par- che vici nity of che Ocean Reef oucler shows mecli aced in pare by acmal nucrient concenci cul are orga ni cs and phyrop lankton are char che discharge comm only elevares surface rrarions ro which rhey are exposed. in clu ded in ch e rransporr equ ation , wirh nucriem and bacceri al leve ls in rhe \Xlhicforcls Typical resulcs from incense wacer column

WATER FEBRUARY 1994

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Figure 2 Estimated increases in population and treated wastewater flows for Perth to 2040. Estimates are based on an average rate of population increase of 3%, as well as the deep sewerage of the remaining 25 % of Perth that ispresently 1msewered : : : : 11111 11 ;::111111:\ 111111 \ I ! Ll l I I I l I lII

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WIND AND SEA CONDITIONS

Top: 5.6 cm/sec at 190°

Wind : 12 - 15 knots from NNW

Bottom : 5.7 cm/sec at 164°

Sea : 2 - 3m swell

Figure 3 Simulated S111/ace flow patterns in Perth coastal waters after 48 hours under

constant conditions. Note the dominant south-wards flow of offshore waters (Greater thttn 20m) regardless of wind direction. Also, ctn eddy is·generttted south of Rottnest Island 11nder most conditions.

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Figure 4 Tin in water colutnn along plumeaxis: O~ean reef- 10 Augmt 1993 26

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stud ies of stati c ~ ucrient levels in winter support these views (Figure 4), where the surface plume is clearly defined up to 750m from the outfall, and where complete mixing has occurred about 2.2 km away, and where nutrienr levels in bottom waters are consisten tl y lower than chose in surface waters.

Many of these processes have been averaged for represencacion within che COASEC model, where , for example, the model portrays a two-layer sysrem with a constant depth of 3m ascribed ro che upper layer. In addition , COASEC provides a constant hori zo ntal diffus ion c.oefficienc whi ch is nor dependent on wind srrengch or direction.

Ecology. The main processes of signi ficance whi ch are includ ed in the COASEC model are shown schematically in Figure 5.

The mod el represents the stimulation of primar y production of 5 se parate plant gro ups. These are: phytoplankton; 2 species of seagrasses namely Posidonitt and Atnphibolis; and 2 groups of macroa lgae, namely kelp which includes Sttrgassum and Ecklonitt, and macroalgae assemblages, which includes all ocher macroalgal species. Epiphycic growth occurs on seagrass leaves , and fi eld studies distinguish filamentous, fol iose, and encrusting forms , even though epiphyces are considered as a single group in the model.

Particulates can be formed from eroding or decomposing plane material, while organic mate ri al that se ttle s to the sea floor is included in the dw ical pool, and is available for remineralisacion.

Li g ht attenuat ion wit hin the water column is .j! feature of major concern, with any reductions in light to seagrass leaves due co shading (especially from epiphyces) of importance.

The model is not able to represent subtle changes in co mmuni ties of plants and animals. For example, it is known that one of the fi rsc indicators of nucrienr enrichm ent in these oligot rophi c waters is the in creased presence of green algae such as -Chladophora.

Viva, and Enteromorpha. Such information is collected as pare of a routine sampling programm e close co, and at a distance from, the outfalls .

The COASEC ecology module calculates responses over differenr time scales. Phyroplankton concentrations (and therefore light) are calculated for each three hour period , while plane growth and animal responses are calculated each day, or even each week. Apart from the phytoplankton, all of the ecological features that are represented are sessile planes, animals, and detritus .

Each of the 25 0m x 25 0m grid cells in the model is ascribed one habitat type. The matrix used co prepare the habitat allocation includes fiv e ge omor'pholog ica l uni cs, namely: sand , pavement, low reef, high reef, and coastal platforms. Sandy substrates can be defined as bare, or with seagrass meadows (either Posidonitt or Amphibolis). The remai ning unit s are all hard substra tes , and are defined in terms of cover by kelp or macroWATER FEBRUARY 1994

CIRCULATION MOONG EXC HANGE

LI GHT

lll

PHYTOPLAN KTO N

EPIPHYn-:s

T•

FI LTER FEED ERS

~EAG RASSES 2 Six,cics

SEAWEEDS -Kelp

-M acro-algae

Figure 5 Marine processes inc!Hded in the COASEC model

algae. Field information used to define these coastal zone policies and warer quali ty guidehabitat types has been mapped at a scale of 1 1ines , simpl e and effective procedures fo r in 10000, using a rec tified im age from a managi ng nutri ent di scharges to coas ral warers srill elicit much debate.

GEOSCAN MkII image.

For rhe area around rhe rwo northern outThe "Ass im ilarive Capacicy" approach, fa lls, approximate habi tat disrriburi ons are: initially much supporred, has virtually disapseagrasses 14%; sand 48%; hard subsrrares peared from rh e lirerarure, and has been 38%. There is no seagrass within 4km of the replaced by more general policies such as rhe southern ourfall (Cape Peron). Inirial model "Precautionary Pri nciple". However, none of condi ri ons, as well as data for model valida- rhese policies has been convened inro practition and for monitoring, have been obtained cal and purposeful management programmes from local as well as comparable studi es. Sub- char can be applied across a broad range of stanti al season al variation s in biom ass of marine systems. The reason for this is probaimportant primary producers occurs; exam- bl y no more complex than co accept ch ar ples are given in Table 5 (Kinhill , 1993). nurrienr cycl ing processes vary significantly The present detailed fie ld studies will be from place to place, and that the response of providing further model validati on dara, as concern, for example plankton bl ooms, are well as establ ishing reference information for frequently relianr on the right combi nation the future use of indicators for rhe moni tor- of physical conditions (meteorology, oceanoging of incipient eurrophicarion, such as pres- raphy, rai nfall , ere.) and not only on existi ng ence of green algae, community structure of discharges of nutrients.

Perhaps then there is no pressing need to epiph yres, epi phyre to leaf biomass ratios, and sig nifi cance of encrusting epiphyres in co nstruct co mplex marin e manage ment the epiphyre biom ass as measured by epi- protocols , but rather to accept and implemenr the fai rly well -cried process of estabphyre calcium carbonate content.

Empirical esrimares (Sect ion 3) of nutri - li shing appropriate enviro nm ental va lues ent loading rares to these waters indi cate (previo usly know n as benefic ial uses) fo r eurrophicarion unlikely ar present, bur possi- marine systems of concern , and then reguble in the future. Consequently, the forecast- · larly measuring selecred variables within the ing of future infl ue nces is an im porta nt system to ensure the maintenance of these requirement of the PCWS. Laboratory exper- environmental values.

Ir is in the cask of determining which variimentation is being used to determine rhe effects of planes co rhe continuous exposure of ables are to be measured, as well as recommending rhe ranges of "acceptable" values for elevated concentrations of nutrients.

Seagrasses constitute a known "sensitive" rhese variables, char models and the modelplane rype in these waters, with light reduc- ling process are of considerable value. Models tion due to increases in water column rurbid- are valuable cools for integrating rhe signifiiry, epiphytes and algal asse mblages bei ng cant features of complex marine systems, and the main cause for thei r demise. Despite the fo r guid ing measu rement and moni cori ng relatively low seagrass component of the area programmes.

Ph ysical (or hydrodynamic) models are of interest, rhe PCWS continues to use seagrasses as one of rhe importanr indicators of sufficienrly well developed to provide reliable change , bur mindful of the face char rh e es rimares of fea rures such as water column sysrem may be well advanced towards nutri- stru ct ure, and flo ws. Eco log ical models ent enrichment before a decline in seagrasses cannot achieve chis precision, and because of the oversimplifica tion chat is a necessity in is observed. ecological modelling, ecological models are Managing Nutrient nor able to provide forecasts char are suitable Discharges in Coastal for direct use in management. Well designed Systems monitoring programm es are essential to meet Despite rhe inrernarional proliferation of char objective.

WATER FEB RUARY 1994

Refere9ces

Backhaus, J (1985). A three dimensional model for rhe si, lacion of shelf sea dynamics. Dt Hydrog,· Z, 38, 165-11 BBG (1992). 1orchern Mecropolican Waters Study. Me and pesticides su rvey. Report co Water Authority Western Austral ia by Bowman, Bishaw, Gorham. 25pJ Broom, MJ ,Johnson, D, and Maskell, ] M (199 1). Modell as an environmencal management tool for mariculmn Hong Kong. ln Environmental Hydraul ics (Eds. Lee: Cheung). Balkema, pp 87 1-875.

Cheung, W H S, Hung, R P S, Chang K C K, and Kleev, J \Y/ L ( l 99 l ). Epidemiological study of beach water I lutio n and health related bath ing water standards Hong Kong. \Valer Sci. Tech110/, 23 , 243-252.

Environmental Protection Authori ty (1993). Southern Me poli can Waters cudy Prog ress Report. Environmei Protection Authority, \Y/escern Australia.

1-IGM (1992). Cape Peron Ocean Ouclet. Intensive monitor programme 1992 . Report co Water Authority of West Austral ia by Halpern Glick Maunsell. 70pp.

Jaworski, N A (1981 ). Sources of nutrients and che seal, eucrophicacion problems. In Estuaries and ucriencs (! ielson and Cron in). Humana Press.

Ki nhill (1 99 1). Nort hern Metropo litan \Y/a ce rs Stu Beenyup Outlet. Impacts of the existi ng ouclec. Repor \Y/acer Authority of Western Australia. December 19 l7pp.

Kinhill 0993). PC\Y/S Project E2 . Time series changes marine communities. Review of COASEC e ology m0< Unpu blished report co WA\Y/ A. Oct l 993, 5pp.

Lord , D A (l 993). Models for the long term managemem Perth coastal waters. Proceedings: 15th Federal Conv cion A\Y/\Y/A , April 1993. Vol II , pp 578-584.

HMRC (1990). Austral ian guidelines for recreation.al us, wacec. (National Health and Medical Research Council c ixon ( l 993). ucrients and Coastal Waters - coo much , good thing. Orea1111J 36: 38-47.

Pacciaracchi, C, and Backhaus, J (1992). Circulation pam on the cont inental shelf off Perch Western Auscra Application of a 3-D baroclinic model. U\Y/A , Proce ings 6th lnrernacional Biennial Conference on Physic: Estuaries and Coastal Seas, Dec 1992, Margaret Ri WA,pp 23 l.

Pacciaracchi, CB, and lmberger, J (199 1). Physical proces, rJie vicinity of the Beenyup outfall. Review and analy Report co the Water Authori ty of \Y/escern Auscra Ce ntre fo r Wate r Researc h, U\Y/ A, Report ~ WP635CP 39pp.

Pearce, R J (199 1). Management of the marine ecosystem Western Australia; An ecosystem approach. Mar. Poll 8111/, 23 , 567-572.

Van Senden, DC (199 1). Review of the physical oceanograJ of Perch metropolitan waters. Report co \Y/ A\Y/ A, 2( plus figu res.

Vollenweider (1975). Input - Output models with special erence co the phosphorus oad ing concept of limnolo Sch weiz Z Hydro /, 37 , 53-84. Walk er, DI , a McComb, A J (l 992). Seagrass degradation in Austral Coastal Waters. Mar. Po/1111. 8 111/, 25, 196- 199. 'I Food Regulations (l 987).

Acknowledgments

The encouragement of the WA Bran of rhe AWWA in rhe preparation of er paper is apprec iated. Special thanks are d to C Parriararchi, D van Send en, D Walk and K Hillman for providing access co da incl uded in unpubli shed repo rts, and co Stearne and C Mellarsh for typing rhe man script, as usual, under duress.

Author

Desmond Lorq is project manager for t Water Aurhoriry of Western Ausrralia's mt ridisciplinary Perch Coasral Waters Study. Ihas worked wi ch industrial, research, and ac demic insrirurions in Australia, Canada a1 Sourh Africa, most recenrly, as Associate Pr fessor of Oceanography, University of Pc Elizabeth , Sourh Africa.

MANAGEMENT

MODIFYING THE PHOSPHORUS CYCLE TO ACHIEVE MANAGEMENT OBJECTIVES IN THE OYSTER HARBOUR CATCHMENT D M Weaver\ L] Pen and A E G Reed Summary

che once-abundant seagrasses have diminished Oyster Harbour, adjacent ro the rown of by up ro 90%. This diminution of seagrass is Albany on Western Australia's south coast, thought ro result from excessive algal grow th , suffers from macroalgal domination because of curring off light ro che seagrass. excessive nutri ent input from diffuse agriculEnvironmenral srndies identifi ed diffuse tural sources. Seagrass beds chat once sup- agricu lrural sources as rhe major conrriburor ported the ecosystem have declined by 90% of nutrients ro Oysrer Harbour (EPA, 1990a). because algae resuicts light reaching rhe eaIn 1990 rhe Wesrern Ausrralian Environgrass. Many of the soils in rhe harbour's carch- mental Prorecrion Aurhoriry (EPA) recomment have received ferriliser applications for mended rh ar nurrienr input ro Oysre r more than 30 years and now 56% have a high Harbour should nor exceed irs assimilarive phosphorus (P) status. Mosr of the P loss from capaciry (Table 1). Specific recommendarions rh ese soils occurs in runoff during in cense were established for each source of nutrients rainfall events. More than 70% of the P lose (indu trial , agriculrural and urban areas) and can be conventionally termed particulate and a rime-frame of four years was sec ro achieve manag ement is now based on runoff and nurri enr load rargers . The agriculrural sector erosion control as well as appropriate fertiliser was all oca red alm osr all rh e ra rger load application . Recent surveys of the condition (99 %) because nurrienr input from indusof the foreshores and riparian vegetation of trial and urban areas was considered negligithe maj or tributary entering the harbour ble (EPA , 19906).

(Kalgan River) highligh t the need for rehabilThis paper examines some aspects of the itation of the river sysrem. Most of the nutri- P cycle in rhe catchment and river sysrem of ent buffering capacity of the river system has Oyster Harbour and argues char rhese can be been depleted through active and passive modified to conrribure ro rhe dual, objecrives clearing, with undegraded buffer remaining of sustainable agr icul rure and lwa lrhi er only on a sma ll parr of rh e river's main warerways. channel. Given char mosr lower order srreams c:urrently have no riparian buffer, rhere is Regional Background The Oysrer Harbour catch ment is domiscope ro modify rhe P cycle rhrough the use of harvesrable buffer scrips adjacent ro screams or nared by a Medirerranean climare, wirh cool upslope. In rhis way nurrienrs can be recycled wer winters and dry, temperate su mm ers. back rn paddocks from which rhey were losr, Annual average rainfall varies from 400 mm rhe life of sueaml ine buffers can be extended in the north ease of che catchment to 900 mm and rhe dual benefits of healthi er waterways near the coasr (Figure l). Mosr rain fa lls from and a contriburion ro susrainable agriculrure April co Occober, with Jul y and August being the wettest months. Gently undulating plains can be achieved. developed predominantly on rerci ary sediIntroduction ments dominate rhe landscape with occasional The pursuit of conventional dryland agri- granitic hills. Duplex soils are common and culrure has contribured ro a decline in water consist of shallow, grey, acidic, siliceous sands quality in Oyster Harbour, next ro the town overlying lacerice and clay high in the land of Albany, Western Australia. The change in scape. Sands and sandy gravels are common at land use from one dominated by narural bush lower elevations with sands in valleys. ro one dom inated by agriculture has brought about changes in soi l ferti lity, catchment Table 1 Catchment area. assimilative capachydrology and subsequently water quality. ity targets. and associated taiget n11trient loss to Yearly application of phosphorus (P) has Oyster Harbour increased agricu lrnral producciviry on rhe natTarget nulrienr urally infertile soils of che catchment and aug- Catchment Assimilative capacity targets (Tonnes) loss (kh/ha) mented the loss of nutrients to waterways. area (ha) Phosphorus Nitrogen Phosphorus Nitrogen The harbour is now dominated by macroalgae <I < 108 <0.05 <0.36 because of che increased nutrient inpur, and 30 092 28

In che main , agriculrure consists of broad scale grazi ng (cartle and sheep) in che south , wirh increased cropping in rhe north. Small zones of intensive agriculrure are located close co regional centres. Ferriliser management practices are generally based on chose developed when che land was first cleared, and includ e annual fertiliser app li ca tion , regardless of soil nmrient starns. Land management usually does not cake inro account pocencial off-site impacts.

Phosphorus in the Catchment Soils Sandy soils were implicared in the eucrophicacion of the Peel-Harvey esrnarine system because of the lat'.k of P-sorb ing substances such as iron and aluminium oxides and clay minerals in the catchments soils . Likewise, early studies of nutrient rransport to Oysrer Harbou r focussed on the siliceous sandy soils

Figure 1 Catchment bo11ndaries of Princess Royal ancl Oyster Harbour with associated streamlines and rainfall isohyets (mm) . Shaded area indirates extent of Kalgan River catchment to ga11ging site.

*D M Weaver, Deparrmenc of Agriculture WATER FEBRUARY 1994

60 (low reactive iron) as being the "most prone co Reactive Iron (ppm) leac hing" and the most likely co require man1l 0-100 50 agement ro reduce P loads (EPA, 1990a).

'1 More convencional thin king focuses on E 100-200 "".c"' 0. :i: -8> 40 the relationship between soil P levels and P 0..

200-400 loss in "runoff' and a number of srudies have :0" "' 30 demonstra ted a close pos itive relati onship Iii 400-800 ti tl>< between these variables (Sharpley et al, 1978; llitl 800-1600 Sharpl ey et al, 1986; Vaithiyanathan and " 20 ~ >1600 C Correll , 1992). Dara collected in the Oyster 0 .0 Harbour catchmenc demonstrate that 56% of @ u 10 the catchm ent's soil s contain P in excess of iii plant requirem ents (Wea ver and Prout , 0 1993).

P status standards Uncleared 1979-1989 1959-1979 Prior to 1959 Further to chi s, the data indi cated chat Time at which conventional fanning began soil P depended on soil reactive iron and che Figure 2 Effect of ti111e 11nder conventional farming practices and soil reactive iron (ppm) on soil length of time that the soil had been conventionally farmed (Figure 2). The highest soil P bicarbonate P (ppm). Soil P statm standards indicating bicarbonate P above or below u1hich P statm is was associated with the highest reactive iron high or low is at fa r left. (> 1600 ppm) for soils that had been far med for similar lengths of rime. In add ition , soi l P ro id enti fy rh e best type and placement of of the river flow occurs in Ju ly and August, was highest where conventional farming had management pracnces. although unseasonal summer scorms resulted been established rhe longest (>30 years). The in rhe highes t recorded flow in January of P in soi ls with low reactive iron changed Phosphorus Transport 1982. The regress ion mode ls showed ch at little after 10 years whilst those with high Major runoff events, lasting a few days , on ly terms related to river discharge (P<0.05 ) reactive iron conci nued to increase after more can account for most of the annual flow to were significan tl y correlated with tota l P. rhan 30 years of P applications.

Oyster Harbour. Coincident with these major The incl usion of a surrogate for the riming of Standards for soil P status whi ch were runoff events is an increase in coral P concen- fertil iser appli cation (% of annual P applied deve loped ro indi ca te P requi rement for rrarion in the runoff waters. The concomitant in each month) did nor improve the model's annual clover-based pasru res in rhe >700 mm increase in coral P conce ntrat ion wi rh river predi ctions or aci d any further sig nifi ca nt mean annual rainfall areas of rhe sourh coast discharge means char most nutrient in pur co terms co rhe model. In aclclir ion , samples colof \YIA (F igure 2) show char status (low, Oys ter Harbour occurs in relative ly few lec ted from runoff plots on three soil types medium or high) is related to ava ilable soil scorm events. In a three day period in July showed no significant effect (P<0.05 ) of P P and reactive iron (P sorption). In low starus 199 1 (<1 % of rhe year) th e Kalgan Ri ve r app li ca tion on• P concentration in runoff. soils, clover exhib its good growth response delivered more than 90 % (3 6 tonnes) of its Thi s, in part, im plies char the prim ary P to applied P. In medium starus soils, clover annual P load (39 tonnes) to Oyster Harbour. source is nor fertil iser, bm is more likely co shows little response to P and in high earns The nutrient load limits set by the EPA be a s~co nd ary so urce such as plant and so il s there is no response co P. The criti ca l fo r Oysrer Harbour cou ld easily have been an imal res idues and soil particulates (Ward et level that defines high P status is exceeded met in 1991 if rhe "sa mpling window " of al, 1989). Alternative reasons for find ing no most ly in rh ose soi ls whe re conventio nal Monday to Friday had nor been extended co effect of fert iliser application on coral P confarm ing has been established for more than incl ude the weekend fo r chis event. centrations in rhe Kalgan River include the 30 years.

Reg ression mod els were used ro deter- dec reasi ng abi Iiry to resolve speci fi e causa l Phosphorus is applied to more rhan 70% mine whether rhe increase in coral P concen- impacts on water quality as catchm ent size of all paddocks, irrespective of whether the tration in rhe Kalgan Ri ver was a funct ion of increases (Ongley, 1982). These scale effects so il P sra ru s was low, medium or hi gh. increased river discharge or fe rtiliser applica- (Prairi e and Kalff, 1986) appear co operate in Nin ety percent of paddocks with a high P tion. Of the P appl ications each year (>2000 rhe Kalgan River catchment and are due in stat us rece ived P app li ca tions, probab ly ronnes; SCEP, 199 1), most is applied at rhe part co crave! rime and the abi lity of the river because far mers do nor want co risk reduced break of rhe season, in April and May. Mose system co assimil ate nutri ents under different production from their best paddocks.

1200 Given ch ar fertiliser manage ment has remained relative ly constant and independent 1000 of so il reac tive iron and soil P starus sin ce fa rming began in the catchment, one might Cl 800 e ask, "where is all rhe P char has been appl ied 'O(IS co rhe low reacrive iron soils )" Ir also becomes .Q 600 evident from Figure 2 char the soi Is char have a. ~ 400 rhe grea resr "pote ntial '' co lose P are chose 'iii 0 char have high reactive iron and a long fer• ' 200 tiliser hiscory, if they are prone co eros ion .

These high react ive iron soil s have scored I I >, >, Q) .c much of rh e P app li ed co chem ove r many ~ t5 cii cii (IS <ii cii C 'S :::, (IS a. ~ .0 .0 .0 .0 :::, -., (IS ~ :::, Cl 0 yea rs, whilst rhe low reac tive iron soils have -., < E E E :::, ~ Q) 0 Q) Q) ..0 < Q) u > sco red little. Rain fa ll eve nts , parti cul arl y 0 0..

Q) LL 0 Q) z 0 Cl) chose char cause soil co erode, will result in cl] P associated with particulates (>0.45 µm) nutr ient loss commens urate with th e so il 's potential (P score) It is important therefore to Filterable Reactive P (<0.45 µm) determine the dri vi ng fo rces for the movement of P fro m rhe catchment ro its waterFigure 3 Ti111e series shou•ing co11ve11tiont1I separation of P forms transported in the Kalgan River ways and rhe fo rms in which iris transported in 1992

•• • •

I

I.. I

i-

l

•

WATER FEBRUARY 1994

29

flow reg im es (Simmons and Cheng, 1985).

Inirial invesrigarions into nurrient rransport to Oysrer Harbour from its carchment found chat 85 % of the P load was in a soluble form which was readily avai lable for aquatic plant growrh (E PA, 1990a). Our inves rigacions suggesr char 70% of rhe P is transported in an in so luble form (Figure 3) and recen tl y published papers offer valid reasons as to why chis is an underesrimare.

Figure 3 shows a recent assessment of rhe nurri ent load discharged from rhe Kalgan River to Oysrer Harbour in 1992. Standard methods were used and included the fie ld fi lcration of samples rhrough O.4 5µ.m fi lters and analysis of sampies for reacri ve P as well as rhe determinarion of coral P on unfiltered samples. The difference berween total P and fi lrerable reacrive P is conventionally termed particulate P. Sediment concentrations were also derermined on separare sa mples. In excess of 4500 tonnes of suspended sediment were discharged from rhe Kalgan River to Oyster Harbour in 1992, a year of relati vely mild flow conditions.

Recent publications highlight problems associated with rhe choice of 0.45µm fi lters as rhe arbitrary separation between "particulare" and "dissolved " fracrions (Douglas et al, 1993; Oliver et al, 1993) and the tendency to ignore the < lµm in rhe derermination of sediment loads and therefore underestimate the particulate load and overesrimare rhe dissolved load (Harr et al., 1993).

Douglas et al (199 3) sca res ch at "rh e common definition that material present in solutions chat have been filtered through a <0.45µm filrer as being 'dissolved ' is nor correcr.

Colloidal species at lease two orders of magnitude smaller than 0.45 µm can be fractionated from such solutions. The term 'disso lved ' must be applied wirh far mor e caurion in rhe definirion of filrered material. " Given rhe fo regoing, much of whar would normally be termed "soluble" Pis likely to be associated with fine colloids.

The Loss of Natural Streamline Bio-filters The realisation char mosr of rhe P los t from farmland is conveyed to downstream waterways via particulare transport has highlighted the value of vegerated buffer scrips in rhe bio-filrering and energy dissiparion of floodwaters (Troeh et al, 1980; Odum, 1990; Thorn e, 1990). Erosion and subsidence (Thom e, 1990) muse contribute signifi cant quantir ies of P-rich particu late matter to warerways, but the roors and rhizomes of riparian vegetation will support embankments. Th e loss of screamline vegerarion rhrough active clearing and livestock grazing nor only reduces the bio-fi lteri ng capacity of rhe scream ecosysrem bur can bring about grearer flow velocities as the water moves downstream unimped ed by vegeration (Thorne, 1990). The greater rhe speed of the warer, the grea ter is its capacity to cause 30

Table 2 Smmnary statistics for the Kalgan River Year

Flow

P load

Flow

(L x Ill')

(tonnes)

d ays

70 75

39 9.2

umber

Maximum daily

Max imum

fl ow

instantaneous

of flow events

1991 1992

1

28

erosion and carry the resultant sedimenr.

Initi al clearing of scream lines of th e Oysrer Harbour carchment would have concenrrared upon rhe minor order screams , which would have been relar ively dry and easily passable by machinery used to clear the landscape. Hence most minor order streams have been cleared entirely of rheir vegetation .

In contrast, higher order screams would have been generally weHer and rheir deeper valleys would have presented a hazard co machinery, hence they have not bee n actively cleared.

Also, many of these screams have been fenced off to prevent rhe loss of livestoc k in the densely vegetared and ofren deep river valleys.

Th e process of clearing in rhe Oys rer Harbour carchment, and probably all southwest carchments for that matter, has caused rhe loss of buffering capacity againsr nurrient and sed iment loss ar the head of the catchment. This has left the lower secrions of rhe major order screams, and mostly rhe main channel icself, co do the work of dissi paring energy and crapping nurrients and sedimenr.

The main channel is 140 km in lengrh , but its criburari es amount to more than 177 0 km. Generally, only rhe lower portion of the main channel (about 40 km) and some of the major tributaries (about 30 km) are in reasonab le co ndi cion. Hence th e bufferin g capaci ry of rh e drainage system has been reduced co a notional 4%.

Condition of the Kalgan River Foreshores

4

(L

X

Ill')

11.8 .8

P concentration (mg/L)

3.0 0.8

soil expos ure and erosion: (A) pr isrin e to slighdy disturbed , (B) degraded,(() erosionprone to eroded and (D) ditch or drain. This work fou nd chat abour 25 % of rhe river foreshores were A grade, 46% B grade and 29% C grade (Pen, 1993). Therefore, char lengrh of the river repre enting undegraded buffer amounted co so~ ewhat less than 25 km .

Two pieces of evidence ind icate rhe effectiveness of the remaining undegraded buffer in reduci ng nutrient and sed iment transporr.

The first is the effect of catchment size on nutri ent transport . A reg ression mod el of catchm ent size vs P load (log transformed) using dara collected in the Oysrer Harbour catchment showed significant (P<0.05) positive correlations wirh a slope less than 1 indicati ng that unit area P loss rates decreased with increasing catchment area (Prari e and Kalff, 1986). Given the foregoing discussion, the larger catchments are more likely ro have greater lengths of higher quality buffer rhan smaller catchm ents and provid e a greater opportu niry for nurrient assi mi lati on. The second is summarised in Table 2 and shows that for years of similar flow there are marked d iffe rences in nutrient load. When rh e number of flow events and flow days were small (1991), the maxim um dai ly flow and max imum. in stantaneous P co nce ntration were high.

Conversely the maximum daily flow and maxi mum in sta ntaneous P co nce ntra tion

The loss of streamline vegeration continues coday, mainly through passive clearing.

The dereriorarion of fencelines leads to livescock gai ning access co rhe ri parian zone where rh ey graze and trample the native plant species. Over rime, with the encouragement of freq uent fires , rhe native plants are replaced by weeds, mainly ephemeral grasses, which afford only a fraction of rhe buffering capacity of char of the original vegeracion and provide negligible smam bank supporr.

As th e natural scream buffers are degraded, nutri ents and sediment captured and consolidared over many years are released into the river sys tem , compoundin g the loss of fresh material from rhe surrounding farm land.

D grade: ditch In rhe spring of 1992, the more vegetated lower reach of the Kalgan River was surveyed over 94 km co derermine the effect of passive clearing on the foreshores.

Foreshore condition was assessed using a sysrem which reflects the general process of river valley degradarion , from prisrine river Figure 4 River foreshore condition divided to eroded dirch, illustrated in Figure 4. The into fottr stages or grades following the general . sysrem categorises a section of foreshore inco process of river valley degradation from pristine four grades on the basis of weed infestation , river (A) to ditch (D) Fene.dollandwffdin!Hted

WATER FEBRUARY 1994

nutrient expon

7

(a)

from animalfrum products in nutrient input

from feniliser

!

.

watercoursm.'.'.. e----::::::::::::::==

nutri ents

entering soil from feniliser

-

nulrient and soil loss from Crum to

nutrients recycled into soil from animal waste

erosion and undercutti ng of bank soil P status is high

nulrients lost beyond the root zone

(b)

nutrient expon from frum in animal products

lateral buffer recycling of harvested material and nutrients back to frum nutrient and soil

loss to buffer slrip

nutrients

recycled into soil from animal waste

nulrients entenng soil from ferti liser

j

... nutrients recycled into soil from plan t death

soil P status is mediu m

nulrients lost beyond the root zone

Figure 5 The P cycle in (a) altered and (b) modified agrimlt1tral landscapes

we re much lower in 1992 when the same volume of water was released from the catchment in four smaller events and over a longer rim e. Hence in 1992 th ere we re mu ch grea ter opportuniti es fo r nutri ents co be assimilated by sed imentation and bi ological uptake in the lirroral zone (Simmons and Ch eng, 1985) . The grea ter oppo rtunities would have been provid ed by the longe r crave! rime, reduced velocity, lower energy, greater sed imentation and rhe increased rime of shallow water depth fo r the period when flow events occurred (Simmons and Cheng, 1985). Th e effec t of var iable source area (Ward et al, 1990), dominating water flow path (runoff vs infi ltration) and the fact char the river system may be a source or a sink of nutri ents (Berndrsson, 1990) may also be important in determining diffe rences 111 nutrient loads for years of similar flow.

The firs t part of the P cycle that can be modi fied is P input. Given char more than half of the soils in the catchment have a high P sca ms, there is no biological benefit in applying P ro these soils. Through the use of soil resting far mers can adjust soil P ro a level char optimises profit and productivity and minimises the risk of P loss. Some $2M could have been saved in one year by rhe rural comm un iry if P app li ca ti ons had bee n made according ro soil resti ng . This money could then have helped ro add ress other nutri ent deficiencies (sulphur and potassium) and soil acidity problems.

The second part of rhe P cycle char can be modified is that which relates ro P loss.

When nutrients are applied ro soil, some of ir remains in rhe soil , some of it is used by pasture and eaten by animals, and some of ir' is lose. Some of the nutrients used by pasture and animals can be used again because when Modifying the P Cycle planes die and animals defecate, some of it is The P cycle can be mod ified ro reduce rhe returned ro rhe soil. The planes and animals loss of a valuable resource and red uce the provide a way co recycle the nutrients (Figure impact of nu trients on downstream warer- 5a). Some nurrienrs are nor recycled and can bod ies. In rhe Oyster Harbour catchment rhe be lose forever as farm produce. In rhe case of natural P cycle has been altered over the lase the Oyster Harbour catchment, nutrients are 30 ro 50 years and is adapting ro rhe com- also lost in runoff as erosion products. bined effects of a changed hydrology, so il Beca use there are concu rrent effec ts of chemistry, physical environm ent, ecology and scale (Prarie and Kalff, 1986) and in scream water quali ty. The vecrors for nutrient input, processes (Simm ons and Cheng, 1985) on recycling and loss have changed in magni- nutrient loss, it is very likely char estimates rude and fo rm . However th ere is scope ro of nutrient loads entering Oyster Harbour are modify th ese ro co nrr ibure ro catchment up ro two orders of magni tude lower than management objectives. char lose from agricultural land ro rhe catchWATER FEBRUARY 1994

menrs wa~rways. This implies that the 1 of nutrients through ru noff and erosion ref senrs a very high economic burden to rura l comm unity in th e Oyster Harb< catchment (approx . $1.5M ann ually).

The use of fenced perennial buffer srr either adjacent ro screams, or upslope, i: vides an avenue to trap som e of the nutriE los t throug h runo ff and eros ion (l arE buffer). Ir has been argued that soil and nu enc trapped in buffer srrips are lost from ai culcure fo rever, unless they are mechanic tra nsported back ro paddocks (Di llaha : Hayes , 1~92). Ir is possible, however, r some of rhe nurrienrs can be returned ro p docks by harvesting plane material within buffe r for srockfeed (Figure 5b). Buffe rs unlikely ro requi re fertil isation as they contin uously supplied with nutri ents fr farmland upslope and upstream. Ir would preferable char buffers ad jace nr ro srrea were not grazed because farm animals assi. late only small quantities of ingested nu enrs (Djajanegara et al. 1984). Faecal depo would recycle nutrients ro the buffer, rat than ro the paddock. Addirional buffer st1 upslope in paddocks would resrricr nutrit and soi l entering srreamline buffe rs, all graz ing, keep nutri ents in paddoc ks : extend the life of streamline buffers. There! buffers can provide direct and indirect bE fi rs (shelter) as well as the potential ro c. rhe nutrient cycle (Lefroy and Hobbs, 199: Prorecrion or rehabilirarion of vegerat along strea mli nes will fu rther attenuat loss fro m far mlands (long irudinal buff Sutoh vege tated buffer scrips along mi order streams can be very effective at in cepring sediment and nutrients passing fr rhe ad jacenr fa rmland s (Howard -Wi lli, and Downes, 1984; Peterjohn and Corr 1984; Howard-Wi lliams et al, 1986; Coe et al, 1987; Hee de, 1988 ; Kn auer r Mander, 1989; Magette et al, 1989) and \ ecati on within the streamlines themsel causes energy dissipation which leads ro s< menr trapp ing and increased trave l ci t (Howard Williams et al, 1986). These F cesses in rurn increase nutrient recycling sp ira lling whereby nut rient parti cles ass imil ated and subsequentl y released li ving things as th e particles move do, stream (Pinay et al, 1990; Pi eczynska, l 9' In this way large quanriries of Pare no !or. qui ckly transfe rred downscream ro poll waterways.

Alo ng rhe major orde r screa ms de nat ive vegetati on should be protec ted rehabilitated, not only for bio-filtering, also to support rhe screa m banks agai erosion and subsidence and ro support burgeoning tourism indusrry and main1 local amenity.

Because buffer scrips have on ly a fit capac ity to assim il are P, ir is necessaq create buffers which can be harvested so 1 nutrients can be recycled. As a first lirn inrerceprion, narrow buffe r strips could used for intermittent grazing or hay or sil

production. Bu ffe rs of nat ive vegerar ion which receive lower levels of P could be harvested for wood (ie fence posts, firewood , ere) or wi ldflowers. In rhe long term , harvesting of buffe r strips and rhe recycling of P back ro fa rmlands are essential, otherwise buffers wil l become a reservoir and source of nutrients as signi fica nt as ag ricu ltural soils, ul tim ately reaching an equil ibrium scare whereby rbey lose as much P as rhey captu re.

Acknowledgments The authors acknowledge rhe assisrance of South Coast Estuaries Project Group, in particular Ashley Proue, Tony Cremin (who prepared Figure 1) and Peter Hocki ng, and the Water Au thori ty of Western Australia in rhe collecrion of info rmation assoc iated wirh rhis article. Thanks also ro Ross George and Don Mcfarlane for their helpful comments on rhe manuscript.

References Berndtsson, R (1990) Transporr and sed imentation of pollutants in a river reach: a chemical mass balance approach. \Vt1ter Resoul'ces Reseal'ch 26(7), 1549-1558 Cooper. J R, Gilliam, J WI, Daniels, R B and Robarge, \XI P (1987) Riparian areas as filters for agricultural sediment.

Soil Science Society of Amel'ic" Jou m aI, 51, 4 16-420 Dillaha, TA and Hayes,J C (1992) Vegetative fi lter strips: II .

Applicat ion of design procedu res. ASAE Paper No 922103 Djajanegara, A, Molina, B T and Doyle, PT (1984) The uti lisation of untreated and calcium hydroxide treated wheat straw by sheep. A nimal Feed Science and Technology 12, 141-150 Douglas, G B, Beckett, R and Harr, BT (1993) Fractionation and concentration of suspended particu late matter in natural waters. Hyd,.ological P1Vcesses, 7, 177 -1 91 EPA (1990a) Albany Harbours Environmental Study, 19881989. Bulletin 412, Environmental Protection Authority, Western Australia EPA (19906) Recommendations of the Environ mental Protection Authority in relation to the environmental problems of the Albany Harbou rs. Bulleti n 4 2, Environmental Protection Authority, Western Australia Hart, B T, Douglas, G B, Beckett, R, van Put, A and van Grieken, R E (l 993) Characterisation of colloidal and particu late matter transported by the Magela Creek system, northern Australia. Hyd,.ological Pl'ocesses, 7, 105 -11 8 Heede, B H (1988) The influe nce of vegerarion and its spatial distribution on sediment deli very from selected Arizona fo rests and wood lands. Erosion control: stay in ru ne. Proceed ings of Confe rence XIX , Arizona Stare University Howa rd-W illia ms, C and Dow nes, M T ( 1984) Nutrient removal by stream bank vegetation. In "Land treatment of wastes: proceedings of a seminar." R J Wilcock (Ed), Water and Soil Di recrorate, Minist ry of Works and Development fo r the National Water and Conservation Authority , Well ingcon. Water and Soil Mi scellaneous Publication, 70, 409-422 Howard-Williams, C, Pickme re, Sand Davies , J (1986) Nut ri ent rerention and process ing in New Zea land Strea ms: the infl uence of ripa ri an vegetat ion. Ne ll' Zealand Ag,.icultuml Science, 20, I 10-11 4 Knauer, N and Mander, (1989) Stud ies on rhe fi ltration of differently vegetated buffer strips along inland waters in Schleswig-Holstein I. Filtration of nitrogen and phospho. rus. Zeitschl'if t / 111' K11/t11 1'tecknik 11nd /.,ande11tll'ickl1111g, 30, 565 -376 Lefroy, T and Hobbs, R (I 992) Ecological indicators for sustainable ag riculture. Australian Soil and \flr1 ter Consel'vation 5(4), 22-28 Magette, \YI L, Brinsfield , R B, Palmer, R E and Wood , J D ( 1989) Nutrient and sediment removal by vegetated filter strips . Tra ns. Am. Soc. Ag. Eng., 32, 663-667 Odum, \XIE (1990) Internal process influencing the maintenance of ecorones: Do they ex i r' In "The ecolog)' and management of aquatic-terrestrial ecocones". Man and the

32

Biosphere series Vol . R T Naiman and H Decamps, UNESCO. The Parthenon Publishing Group, Paris. pp 91- 102 Ongley, ED (1982) Th e PLUARG expe ri ence: scientific implications for diffuse source management. In "Wiater quality management: moniroring programs and diffuse runoff." B T Harr (Ed). \Y/arer Studies Cenrre, Chisholm Institute of Technology, Melbou rne pp 87-10 I Pen, L J (1993) Condition of the Kalgan River foreshores.

Albany \'(larerways Management Authori ty, Waterways Commission Report. (in press) Pererjohn, \XI T and Correll , D L(1984) Nutrient dynamics in an agricultural watershed: observations on the role of a riparian forest. Ecology, 65 , 1466-1475.

Pi eczynska. E (I 990) Lentic aquatic - terrestrial ecorones: thei r srruccure, function and importance. In "The Ecology and Management of Aquat ic - terrestrial Ecorones". Man and the biosphere Series Vol. 4. Eds R T Naiman and H Decamps. UNESCO. The Parthenon Publishing Group, Paris. pp. 65-89.

Pi nay, G, Decamps, H, Chau vet, E and Fusrec, E ( 1990) Functions of ecorones in fluvial systems. In: Ibid .

Prairie, YT and Kai ff. J (I 986) Effect of catchment size on phosphorus ex port. \V" ter Resourres 8111/etin, 22 (3), 465-470 CEP (1991) Reducing the nutrient load from rural sources ro Albany's Harbours - Draft . Western Australian Department of Agriculture Sharpley, A 1, Syers, J K and Tillman. R \V/ (1978) An improved soil sampling procedure for the prediction of dissolved inorganic phosphate concentrations in su rface runoff from pasture.) Environ. Qu"I.. 7, 455-456 Sharpley, A N, Smith, S .J and Menzel, R G (I 986) Phosphorus criteria and water quality managemem for ag ricultural watersheds. Lt1ke Reserv. M" nngt., 2, l77- 182 Simmons, B Land Cheng, D M H (1985) rate and pathways of phosphorus assimilation in the Nepean River at Camden, New South Wales. \Va tel' Resenl'ch, 19 (9), 1089-1095 Thorne, CR ( 1990). Effects of vegetation on riverbank erosion and stability. In: Thorne, C R (Ed) Vege tation and Ernsion. Jon Wiley & Sons Ltd. pp. 125-143.

Troel1, FT, Hobbs, J A a.r.d Donahue. R L (1980). "Soi l and \Xlater Conservation: ~r Productivity and Environmental Protection. " Prentice-Hall , New Jersey.

Vairhi yanathan, P and Correll , D L (I 992) The Rhode river watershed: phosphorus distribution and export in forest and agricultural soils. ) E111•iron. Qua/. 21, 280-288 Ward, J C, O'Connor, K F and Wei- Bin, G (1990). Phosphorus losses through transfer, runoff and soil erosion. In "Phosphorus requirements for sustainable agriculture in Asia and Oceania" - proceedings of a symposium, 6- 10 March, 1989:167-182 Weaver, D M and Prout. AL (1993) Changing farm practice to meet env ironmental objecti ves of nutrient loss tO Oysrer Harbour. Fertiliser Resea,.ch (in press).

Authors David Weaver is a l?esearch Olfiter with the \Vestern Australian Department of Agrimlt11re.

He is mrrently investigating the mechanis111s for nutrient loss from farmla11d to Oyster Harbour and I/Sing these to contribl/te to the establishment of Sl/stainable agrimlt1tral systems.

Dr Luke Pen is an Environmental Officer with the Albany \'Vaterways Management Authority. His main area of expertise is riverine ecology and he recently completed a survey of the condition of the riparian vegetation alo11g the Ka/gem Rive1'.

The results of the sl/rvey are being med to promote better management of the river system.

Adrian Reed is a Technical Officer with the Western Australian Department of Agrimlture.

He provides technical s11pport in the areas of hydrology and water chemistry for the department's smtainable agrimltttral systems program in the Oyster Harbour catchme~t

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TECHNOLOGY

LARGE SCALE CATCHMENT MODELLING TO PREDICT THE EFFECTS QF LAND USE AND CLIMATE Report by M Sivapalanf N R Viney Abstract

water resources. However, major bauxire reserves also exist in rhe eastern, lower rainfa ll (< 1100 mm per year) portion of rhe norrh ern jarrah foresr where soil sa liniry values are such char rhe potential may exist for furnre minin g ro ca use signfica nr increases in scream saliniries.

Compounding rhese concerns for Wesrern Ausrralia's warer and land use managers are recent climare model predicrions of possible long-rerm changes in rhe mean annual rainfall for the region, due ro changes in rhe greenhouse effecr (Pittoch. 1988). long-rerm monitoring of a number of small experimenta l carchm ents in rhe stare has resu lred in considerab le knowledge and understanding about rhe effecrs of land use changes on warer yield and sa linit y. Howev er, as ye r, such knowledge and undersranding have nor been urilised ro develop predictive models that can be used by water planners co srudy rhe effecrs of land use and climare changes on rhe quanIntroduction riry and qualiry of warer resources. l and degradarion and scream salinisarion, The aim of th e l arge Scale Catchment due co foresr clearing, are now recogni sed as Mod elling Proj ec t is ro develop a robusr, major environmenral problems in many pares long- rern1 (25 co 50 years), large scale (30 co of Ausrralia. The replacement of native, 3000 km 1), carchment warer and salt balance perennial, deep-rooted vegetation with model (with a daily rime seep) for predicrive annual, shallow-rooted agricultural pasrures purposes. The adopred mod elling approach and crops, causes a reduction in evaporranspi- has rhe fol lowing features: rarion, which, in turn, lead s ro in creased • Ir is based on a disrribured framework, in groundwarer recharge and rising water rabies. which rhe building blocks are 'subcarchTh ese rising wa ter rabies mob il ise salt ments ' of abour l co 5 km 2 in area. deposited within rhe so il profile and trans- • Boch rhe surface and subsurface interconport it co the land surface, and into streams, necrions berween rhe subcarchments and leading ro in creased screa m aliniries and rh eir assoc iared moisrnr e sror es are land degradation. defined explicirl y. land use management practices of • The 'build ing block' model, inirially, is of Wesrern Australia 's northern jarrah forest rhe conceptual rype, wi rh irs paramerers have also co me und er close scrutiny over being esrimared by calibrarion. However, rece nt years ro determine rheir impacr on ir is intended ro derive rhe "consri turive" srrea mfl ow and sa lin ity. Bauxite mining relarionships required ro complere rhe which com menced in 1963 in the Hi gh specificarion of rhe subcatchment models Rainfall Zone( > 1100 mm per year) of by integ raring process-based descriprions Penh 's water supply carchments has been one of hydro logic processes operaring ar such land use which has been closely studied. smaller spaci al and temporal scales.

Studies have shown chat mining and subseThi s modelling srraregy has rhe advanrage qu ent rehabilitation operar ions have not . of "conceptual" models in char it minimizes caused any signfica nt adverse impacrs on rhe rime req uired co obrai n a mode l which A l arge Scale Carchmenr Mod ellin g Projecr was commissioned in Seprember 1992 ar rhe Centre for Water Research of rhe Universi ry of Wesrern Ausrralia, with financia l support from rhe Warer Authority of Western Australia and ALCOA of Au stral ia. Th e objective of rhe project is co develop a catchment yield and saliniry model capable of predicting rhe hydrologic responses of large, hererogeneous catchments (30 co 3000 km 2) in rhe somh-wesr of Wesrern Ausrralia , co land use changes (e.g., deforesrarion for agricul rure , mining operarions), und er various projecred cl imare change scenarios. This arricle presents rhe merhodology adopred for chis modelling , and early results from rhe applicarion of rhe model co a number of small and med ium-si zed carchments which have undergone co nsid erab le changes in foresr cover in rhe last 15-20 years .

WATER FEBRUARY 1994

Effects of salinity on a Westem Australian stream. can give a global view of rhe problem being address~d. On th e other han d, since ir arremprs ro link rhe subcarchmenr-sca le mod els ro smaller-scale phys ica ll y- based descriptions of key hydrological processes, it also ensures a connection ro process physics in terms of both model structure and the mathematical descriprion of individual processes.

Description of Large Catchment Model The large catchm en t to be mod elled is conceptualized as an ordered collecrion of subcarchments (1-5 km 2 in area) where rhe ordering of the subcarchments is wirh respecr ro rheir posirion on rhe stream nerwork char drains rhe catchment. Each subcarchment is associated with a scream link. External links define first ·order, headwater subcatchments, whil e inrernal links define hi gher order, inter-basin areas. The choice as ro the sizes-of the subcatchments, as well as the densi ry of the stream network , is determined by the length scale of heterogeneities such as land cove r, soil properties, rainfall ere, by rhe spatia l scale at which the outputs are required for planning purposes, and by compurarional considerations.

The building blocks of the large catchment model are lumped, 'conceptual' models appli cable at the subcarchmenr scale. The

* M Sivapalan - Centre for Water Research, Universiry of Western Australia 33

subsurface runoff ~ nerared ar rhe inrerface berween rhe perm eable, sand y-gravell y Ahorizon and rhe relati ve ly im pe rm eabl e, clayey B-horizon.

[5J Parr of the in co ming precipirario n is DI From Evaporation intercepted by above ground veg eracive Canopy biomass (leaves, seems ere) and is evaporated back, leadin g co an ' inc ercep cion loss ' .

Grou nd Ground prec ipi cacion (precipi ta tion minus Pre<iplt.Uon interception loss) is partitioned into surface runoff and surface infilcracion. Surface runoff Contributing is assumed ro cake place by boch che infi ltraArea tion excess and saturation excess mechanisms. ~c Infiltration excess runoff is depe nd enc on a surface infilt ra tion ¡capac ity of ch e so il , while sacuracion excess runoff occurs from pares of che cacchm enr (contributing areas) Surface Runorr nfiltration xccss which are sacuraced at the surface by the rise of a perched water cable (represented by che A srore).

Th e water infiltratin g throu g h the ground surface percolates down co che level of rhe clayey B-horizon soil. Thi s percolating warer is rhen parririoned inco deeper infilrrarion through rhe clayey B-hori zon, and subsurface runoff whi ch is ge nerated ar th e interface berween rhe A- and the B-horizon Catchm ent-scale so ils. The subsur face runoff so ge nera ted Infiltration Capacity fl ows down slope and co ntribures co rh e f*ss growrh of rhe perched water cable, which is represented in rhe model by rhe A score. The Deep fj7 "'111 Jnn llratlon ~Mlil warer ch ar in filrra res in ro rh e cla yey Bhorizon soil, on rhe ocher hand , conrribures ro che buildup of the F srore. Boch rhe A and F scores recharge water down ro rhe deeper, more permanent groundwarer cable (repre[] sented in r~ model by rhe B score) The B ~ Eva orati on F STORE tonnnow srore, in rum, continuously discharges warer In D from FS tore ro rhe A srore, represenring a loose connecRecharge tion berween rh e rwo sa rurared moisrure [!i][Dll from FStore Discharge srores. The bulk of rhe srreamflow is conto A Store rribured ro by rhe perched warer sysrem (A srore) in rhe form of subsurface srormflow.

Recharge Leaching p STORE 0 Evaporarion is assumed co cake place from all from A Store c,r, +(AS,), Mobiliiallon (6S ) m 8 2 three scores, their amounts depending on rhe ~lml - - - - - - -,} . - - - Total Runoff relarive levels of moisture in rhe srores, bur ~ Evaporat io n B STORE modified by rhe assumed disrriburion of rree (iJ fr om B S to re roors within rhe soil profile. This compleres rh e entire cycle of hydrologic processes Figure 1 Structure of the rnbcatch111ent-scale, coupled water and salt balance 111odel caking place in rhe carchmenr .

The response of a subcarchm enr would, inputs ro the subcatchment models are daily effecrively, be rhe collecrive responses of rhe rainfall , pan evaporation and an effe cti ve Subcatchment Model rhree so il moi srure scores A, B and F co clearing value or an effective greenness value.

Figure 1 presents the srrucrure of rhe clim ari c inputs, and of rhe inreracrion s Digiti zed ropographic data are req uired ro coupled warer and sale balance model, which betwee n them. These are described in rhe define the subca tchm ents and the strea m is used as rhe building block fo r rhe large model through a number of "consr irurive" network, and ro extract geomorphologic and scale carchm ent mod el. Onl y a brief sum- relati onships, rhe funct ional fo rms of which hydraulic geometry information needed ro mary of rhe model description is presented in have been assumed based on intu ition , or build runoff routing models for the scream chis paper. For more details abour the model from previous work. They incl ude a number network. Examples of the outputs from the and irs performance, rhe reader is referred ro of unknown parameters whose values are mGdel are, for each of the subcatchments, and Sivapalan et al (1993). rhen estimated by a process of 'calibrarion ', for the rota! catchment, surface and subsurThe subcarchm ent warer balance model wherein rhe parameter comb in ar ion ch ar face runoff, actual evaporation, and measures consisrs of rhree interconnected soil moisture gives rise ro rhe besr fir between rhe observed (or indicarors) of the soil moisture status. The scores A, B and F. Score A represents a near- and mode l pred icted srrea mflow values model requires calibration and this is carried scream, perched warer sysrem, while B repre- is selecred. out by comparing the modelled runoff for all sents rhe groundwarer scorage in rhe saturared In order co predict salinities, rhe warer gauged catchments within the large catch- zone below rhe deeper, permanent groundwa- balance model is coupled co a sa le balance ment against the corresponding observed ter table. F represents an intermediate infilrra- model (see again Figure 1). Morivared by rhe runoff values. rion score and contro ls rh e amount of hydrology and hyd rosa liniry of forested Total Evaporation

Precipitation

~m

i

34

WATER FEBRUARY 1994

500

2500

.....

2000

w.,,• 300

200

ij

1500

!=

1000

100

500

'"""' 1975

1976

1977

1978

1979

1980

1981

1982

1983

1981

Figure 2 Comparison of observed (solid Figure 3 Comparison of observed (solid lines) and model predicted (broken lines) mvmla- lines) and model predicted (broken lines) m1mtlative runoff for Salmon and Wights catchments for tive chloride fluxes for Salmon and V:lights catchthe 1975-1989 period. ments fo r the 1975-1983 period.

I

carchm enrs in Western Australia , the salt balance model assumes a srrucrure char is similar ro char of rhe water balance model, with three subsurface salt srores S,, Sn and SF paralleling the moisrure srores A, B and F. However, in addition, rhe salt model incorporates a supplementary salt store SP to represent rhe salt stored in rhe soi l profi le (the salt bulge or P-store). The model incorporates salt discharges by direct surface runoff, subsurface srormflow, and groundwater flow. The deeper groundwater is assumed co transport salt already in solmion, rogerher wirh new salt mob il ised by rhe leach ing, by rhe rising gro undwater table, of rhe soil salts contained within rhe salt bulge.

Changes in fores t cover are assumed ro affect a number of processes described above, namely ca nopy inrerceprion , infilrrarion capacity of rhe surface soil, and evaporation .

They have rhe grearesr impact on rhe evaporation rare, rhus affect ing the long- term water balance. The model assumes that evaporation from the A srore is unaffected by any changes in forest cover, and that rhe evaporation rates from the B and F srores are proportional ro the relative amount of a 'greenness value'. Red uction of rhe greenness leads ro a reduction of evaporation from rhe B and F stores. This leads, over a period of a few years, ro a gradual increase of each of the three soil moisrure srores until a new, wetter equilibrium is reached.

Compari sons of observations and model simulations of cumu lative srreamflow and chloride flux are presented in Figures 2 and 3, respectively, for both Salmon and Wights carchmenrs . The results ind icate that roca l runoff from Wights carc hmenc was more than double char of Salmon , while rhe roral chloride ompuc from Wights is more than chree rimes char of Salmon's. The model predi c ri ons co mpare very favo urab ly with observed runoff and chloride fluxes over the srudy period on both catchments. In particular, rhe model copes exrremely well with rhe transition from forest ro pasture on Wights catchment. Figure 4 presents , as an ill usrrarion, a comparison of che observed and predicred dail y salt loads for Wights catchment for che period 1981 -1982, about 4-5 years after clearing, indi cating an uniformly excelJene fir.

Figure 4 Comparison of observed (solid lines) and model predicted (broken lines) daily salt (chloride) load for Wights catchment for the I 981-1982 period.

,,,.,

f Ml$CIC1n11J

11'10- 1'

. ltl,-79 .

\91(1. 5"

. .

1913-19 \ 991).91

Sa Logging History

Application to a Mediumsized Catchment

The large ca rchm enr model was th en applied ro rhe Conjurunup carchmenc (3 7.4 km 1 in area), also in rhe sou rh-w es r of Western Australia. This carc hmenc has experienced considerable land use change over rhe past 75 years. The majority of the catchment has been logged, all pares of rhe cacchmenc are periodi ca lly burned ro red uce wildfire hazard , cwo small subcatchmenrs have been silviculrurally thinned, and over the past 15 years ALCOA of Australia have cleared and Application to Two Small subsequently rehabilitated pans of che cacchCatchments menc for bauxite mi ning.

The coupled water and chloride balance The complex and heterogeneous (in space model described above was first applied ro and rim e) land use hisrory on rhe catchm ent Sa lmon and Wights, two adjacent sma ll is recorded in a computer-based geographi c experimental catchments ("" 1 km 2 in area) in information system (GIS) which is capable of rhe forested sourh-wesr of Western Australia. produ cin g di g it ise d map s ro show rh e Th e rwo ca tc hments have been intensely sequence of land use management practices. monirored as part of a long -term paired The maps give rhe year char any point on the catc hment srud y of rhe impact of forest clear- ca tchm ent und erwent one of four major ing on water yield and salinity. Both catch- changes in vegeracion density: logg ing , ments have been instrumented ro meas ure burn ing, clearing for mining and subsequent water and chloride input and oucpur. Wights rehabilirarion , and rehabili carion (follow ing ca cchmenc was cleared of all native fores t minin g) to res rore che forest vege ta ti on vegecarion, except for a small stream buffer, complex. These are presented in Figures 5 ain rhe summer of 1976/77 . A pasture of grass d which show cumulative impacts of operaand clover was establ ished for grazing sheep tions over 15 ro 30 year periods. The model on rhe cleared areas. Salmon catchm ent has then constructs and uses an 'effective ' clearremained as an uncleared control catchment. ing valu e, and a 'greeness ' value , for eac h WATER FEBRUARY 1994

1982

-•urtd 197, .n 1971-IO 1911 - 1)

. . .

191,1-11> 1911-19 1990,92

Sc

ALCOA Clearing History

Sd ALCOA Rehabilitation History Figure S Histo1y of changes in forest cover on Conj111·1m11p catchment (area 3736 ha) show1 ing the most recent year of ( a) logging (provided

by CALlvI), (b) controlled burning to redl/ce wildfire hazard (provided by CALM ). (c) deciring for mining and s11bseq11ent rehabilitation to fo rest (provided by ALCOA ), and (t) rehabilitation after 111i11i11g to restore the forest vegetation complex (provided by ALCOA.

35

3500

3000 2500 2000 1500 1000 500

Figure 6 Discretisation of Conjumnup catchment into 11 s11bcatch111ents.

Figure 7 Effective level of clearing for the Figure 8 Comparison of observed (solid line) main catch111ent (solid line). and for six selected and model predicted (broken line) c1111111lative s11bcatchments. during the 1975-1991 period. mnoff for the Conj11nm1tp ratch111ent d"ring the 1974-1991 period. '"'·~ - - - - - - - - - -- --,

125 - - -

2><C02 raln!al• ,~CO2 pot• nl,a! •••PG'•~on

100

_,,....,___.

_

.-

~C,~c::-:-::>---.. "~ --·

Figure 9 Comparison of observed (solid line)

- - --- - -----

~ Figure 10 Comparison of observed (solid

and model predicted (broken line) 111onthly mnoff line) and model predicted (broken line) daily volmnes for the Conj11rnn11p catchment for the mnoff for the Conj11mn11p catchment for year 1982. period 1974-1991. point by combining the inform ation fro m these land manage men t maps, and an assumed simple forest regrowth model.

The model results presented in chis paper have been obtained by using eleven subcacchments as building blocks. The subcacchment discrecisacion used is presented in Figure 6.

Figure 7 presents che rime variation of the effective clearing values for the main catchment and for six selec ted subca cchm encs.

Figure 8 presents a comparison of modelled vs observed cumu lative runoff for the main catchment over a continuous 18 year period.

A comparison of the corresponding monthly observed and model pred icted runoff values is presented in Figure 9 for the same period.

The dai ly runoff co mpari so n fo r che year 1982 is presented in Figure 10. Overall , the model prediccions are excellent.

Simulation of Climate Change Effects Viney and Sivapalan (1993) have recently applied che catchment water and salt balance model to Salmon cacchmenc to simulate che hydrological effeccs of che long- term climate change char may possibly resu lt from a doubling of CO2 concentrarions worldwide. A climate change sce nario, involving a 10% reduction in winter rainfa ll amount and a 15% reduction in the frequency of rainy days in winter, was assumed. This corresponds ro an increase in rain amount, per rai ny day, of about 6%. The summer rainfall pattern was assumed ro remain unchanged, and potential evaporation was assumed ro increase by 10% year-round. Three clim ate scenarios were si mulated: (a) the current climate (ie lxCO2 36

climate), (b) the 2xCO2 clim ate (both rainfall and potential evaporation), (c) 2xCO2 rainfall and lxCO2potential evaporation.

A se c of five 25-year ra infall sequences was ge nera ted, for eac h climate sce nario , using a sy ntheti c rainfall ge nerator. Th e hydrological respon se was simulated using the catchment model for each of the five rainfall dacasecs generated for each climate scenari o, and ch e correspondin g pot ential evaporation races. The model parameters used for these simulations were che same as chose obtained by cali bration for che period 1975199 1. The initial values of che srores A, B and F correspond ro the lase day of the calibration period. The results of che simulations were then averaged ro eliminate the effects of srochascic temporal rainfall differences among the five time series. The averaged results for cumulative runoff are presented in Figure 11 showing chat the cumulative runoff over the 25-year period has been reduced by 45 % in the 2xCO2 simu lations. As a proportion of the res pective cumulative rainfalls, runoff declined fro m 10.4 % to 6.2 %. When ch e effects of only the reduced winter rai nfall (for 2xCO2), buc not che increased potential evaporation (for l xC O2), were simulated, rh e cumulative runoff decreased to 71% of the current (ie lxCO2) climate.

The rare of transport of sale (CI-) from the catchment also decl ined in the 2xCO2 simulat ions, but not to the same exce nr as the runoff. In the lxCO2model, mean annual sale flow was 12.5 g m-2, while in the 2xCO2 model, it was 7.4 g m-2, a reduction of 41%.

Despite che lowering of rhe permanent water cable as a result of reduced rainfalls, the mean

10

,s

T ime (yea rs)

Figure 11 Mean c1111111lative nmoff at Sal111on catch111ent for three 25-year sequences of synthetic cli111ate scenarios.

annual scream salinity (annual mass of Cldivided by annu al vo lum e of runo ff) increased from 102 mg L-1 ro 110 mg L-1• In ocher words, rhe assumed 10% red uccion in winter rainfall and a 10% increase in porenrial evapocarion , on Salmon catchment, have the potent ial to lead to a 45 % decrease in screa m runoff and a 8% increase in scream salin ity. Given rhe uncertainties in current clim ate scenarios (general ci rculation models, or GCMs) fro m which rhe cli mate change ce narios were obtai ned, and rhe present uncerrainti es in che hydrological model, che above pred iceions should be co nsid ered merely as indications of what might happen if climate does change. evercheless, the predictions are illustrations of che potential usefuln ess of the hydrological model to water resources planners.

Conclusions A large scale catchment model has bee n developed ro predict che effec ts of land use and climati c changes on catchm ent water yield and sa li nity. The model has potential for application ro a wide variety of forested or agricultural catchments. So far che model has been applied ro cwo small catchments, and ro a co mplex, heteroge neous, mediu m- sized ca tchm ent , with very good pred ictions of bocl1 runoff and salinity The model has also been used co simulate ~he effects of possible future climate change.

There are two areas where major improvements are needed ro increase the effectiveness of che model described above. These are, one, the 'conceprual ' nature of rhe model in the sense chat che process-descripti ons used in WATER FEBRUARY 1994

the model are not based on physically- based hydrologic th eo ri~ s, and· two , th e large number of param ete rs that need t0 be estimated by calibration. A programme of fundamental research is currently under way at the Centre for Water Research, aim ed ar improving th e physical bases of both the model srrucrure, and the lumped descriptions of the carchm ent responses. More complex, smallscale distributed mod els are being used t0 describe rhe dominant processes occurring on rhe carcb menr, which are then linked co the lumped , carchmenr-scale, paramerric descriptions of the same processes by a process of 'flux-m atching', and rhe marching of soil moi sture srate var iables. On completion of this basic research, the resulting more refi ned version of rhe model will be applied t0 progressivel y larger catchm ents in the southwest of rhe Scare, up co rhe size of rhe Col lie River Basin (area 25001 km)

Acknowledgements This srudy has been fi nancial ly supported by rhe Water Aurhoriry of WA and ALCOA of Australia. J K Ruprecht, C G Jeevaraj, K Mcinrosh and J Snell provided invaluab le assistance cowards mod el developm ent and implem enrarion . The clear ing and for es r manage ment hisrory information was provided by the WA Deparrrnenr of Conservario n and l and Manage ment (CALM ) and ALCOA of Ausrralia. The \'v'arer Aurhoriry of WA provided hydrologica l data. Th e authors exp ress rh eir sincere gra titude t0 rhese organisarions and individu als for this support.

References Pitrock. B A (1988). Actual and anticipated changes in Australia's climate. In : 'G REEN HOUSE - Pl anning for Climate Change', G I Pea rman (Editor) . CS IRO, Melbourne: pp .\5-51.

Sivapalan, M, J K Ru precht, C G.Jeevaraj and N R Viney (199l). Warer and salr balance modeling ro predicr rhe effecrs of land use changes in foresred carchments. Reporr WP 81 1 MS, Centre for Warer Research. ni of Wesr Ausr, Nedlands .

Viney, N R and M Sivapalan ( 1993). The hrdro logi cal response o( carchmenrs ro simulared changes in climare.

Paper presenred ar rhe lnrernar ional Congress on Modelling and Simulation, Perth. December 199.l .

Authors Both a11thors are attached to the Centre fo r U'later r?.esea ffh at the University of U'lestern A11srralia.

Dr Murugesu Sivapalctn is a Senior Leclitrer in Civil Engineering. He has st11died at the University of Sri Lanka. the Asian lmtit11te of Terhnology. Thailand and Princeton. USA. ll'here he rereived his PhD in I 986. His research interests i11d11de hydrological lllodelling. flood estilllation. effect of land me changes and srale effects.

Dr Neil Viney is a Research Fe/loll'. He grad11ated from the University of Tasmania. and received his PhD fro111 the Defence Force Academy.

Canberra. 011 the wbject of miffoweteo rological 1//oclelling of the 111oist11re rontent of fo rest littei: His interest are ll'ildland fire. u•ater and ene1gy balance 1//odels. remote sensing and geogrc1phiral . illjor111atio11 J)'Stems.

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TECHNOLOGY

SODIC SOILS AND WATER QUALITY: ARE THEY RELATED? ~ TM Skene, ] M Oades* Introduction The quality of water in streams of rhe Mr Lofty Ranges of South Australia has been of concern fo r many years. High levels of di ssolved organic carbon (DO C) in wate r intended fo r domestic consumption necessitate expensive disinfection procedures and can lead to the formation of hazardous substances such as rrihalomerhanes. Di ssolved organic matter may also play a role in rhe tran sport of heavy metals (Malcolm, 1985; Weber, 1988) and pesticides (Stevenso n, 1985). utri ents such as nitrogen and phosphorus have been implicated in causing or conrributi ng to the formation of toxic algal blooms (AWRC , 1991; Creagh , 1992). Turbidity caused by suspended sediments is not only aesthetically undesirab le but can also discolour washing, ca use problems with water heaters , clog pipes and irri gation systems (Oades, 1982).

Although point sources of pollution such as dairies and septic ranks can suppl y hi gh concentrations of DOC to st rea ms, ir has been establ ished in studies of paired catchments in rhe Mr Lofty Ranges in South Ausrral ia and Otway Ranges in Victor ia, th at soils in the catchments are actually the main contributors to stream DOC levels (I elson et al, 1990; I elson, Corsaris and Oades,1990; elson et al 1992). Th e level of DOC in stream water is dependent on the soi ls ab ility to retain DOC against leaching. This in turn is dependent on rhe clay content of rhe soil: rhe higher the clay content, the higher the DOC retention capacity.

The objective of th is stud y was to look at another possible facror which may be involved in controlling the release of organic carbon and orher nutrients from soi l, namely the ionic co mposition of the soil so lution.

Sodium ions cause clay to disperse and thi s dispersed clay can then be transported by water movement. The surfaces of clay particles are more exposed when the clay is dispersed and consequently, desorption of ions and molec ules from these surfaces ca n rake pl ace more readily. If organic carbo n and nutri ents are assoc iated with clay particles , then we proposed that factors which influence clay dispersion and movement would 38

also influence organic carbon, N and P release and/or transport. To rest thi s hypothesis, laboratory studies we re set up to look at rh e effect of the sod ium adsorption rario (SAR) and roral electrolyte concentration (TEC) of a solurion in contact with soil on clay dispersion (as measured by turbidity), organic carbon , N and P release.

0 3-) would be leached or released from the so il independ entl y of organic ca rbon and hence fac tors which influence rhe release of orga ni c carbon will have no effec t on th e release of . If, however, the predominant

800

Experimental Procedure Three soi ls with different clay contents were mixed with salt so lmi ons with a range of total elecrrolyre concentrations and sodium adso rption ratios. Clay suspe nsio ns from th ese soil /so luti on mixtur es were then analysed for rmbidity, total organic carbon , roral N and total P.

600

5' ~

~ ~

:a

400

:0

:i

~

200

0

Results and Discussion

• 0 For all three soi ls, the turbidity of the clay 2 3 6 5 suspension was positively co rrelated with Final SAR SAR and TEC (see Figure l )(Skene and TEC= 1 rrM+il D ,2 = 0.882 Oades, submitted). The hi ghest meas ured turbidities were obtained with rhe treatment • TEC = 3 rrM+il ,2 = 0.879 solutions which had a high SAR and a low • TEC= 5 rrM+il ,2 = 0.925 TEC. This result is as expected from diffuse ,2 = 0.626 TEC = 10 rrM+n double laye r theory : high TECs cause floccu0 lation of the clay particles which rhen settle Table 1 The effect of final SA R on lttrbidity our and the turbidit y of rh e so luti on is (Urrbraesoil). reduced. A high proportion of a on rhe clay surface causes dispersion which res ults in high rnrbidiry.

50 The organic carbon concentrati ons of the suspensions were found to be pos itively corre0 40 lated with turbidity ; the higher the turbidity, the higher the organic carbon concentration (see Figure 2)(Skene and Oades,submirted).

30 Phosphorus concentrations were also posi- 0 0 tively correlated with turbidity (see Figure I3)(Skene and Oades,submitred). This result is 20 nor surprisi ng as phosphorus is st rongly adsorbed by clay particles. Phosphorus concentrations and organic carbon concentrations 25 0 500 750 1 000 125 0 were also positively correlated .

I I irrogen showed similar re lationships Turbidity (NTU) with turbidity and organi c ca rbon as phosphorus for one of rhe soils bur not for all (see Table 2 Relationship between t11rbidity and TOC (Kondoparinga soil).

Figures 4 & 5)(Skene and Oades,submitted).

This may be due to differences in the predominant fo rms of nitrogen present in the *J M Oades, Waire Agri cu ltu ral so ils. Inorganic for ms of nitrogen (NH4 + , Reserach Insrirure.

WATER FEBRUARY 1994

0 .4

3 .0

• E

E Q.

5 z

5

0 .2

•

iij

0

to-

[J

2 .5

0.3

Q.

0..

5

2 .0

E

1.5

5 z

0

0 .1

4

[J

1.0

3

iij

[J

0

'nlo

to-

[J

2 [J

0 .5 r2 = 0.772 0 .0

[J

Q.

iij

to-

[J

[J

r2 = 0.120

r2 = 0.740 0 .0

0

200

400

600

800

10 00

0

Average Turbidity (NTU) Table 3 Relationship betUJeen tttrbidity and Total P (Kondoparinga soil).

form of soil r was organ ic, rh en facrors which influence rhe release of organi c carbon will also influence the release of r

Implications In summary, any facrors whi ch influence rbe dispersion and movem ent of clay are also go ing ro influence rbe release and movement of nmrienrs and organ ic carbon associated wirh ir. Sad ie soils are already wide-spread throughout Ausrral ia and rbe area of sodium affecred soils is continuing ro increase. The resulrs of thi s scudy suggesr rbar unless measures are caken ro hair the sp read of sodi c so il s, water qual iry wil l also co ntinu e ro dec li ne. Sodic soils ca n be am eliorated through the use of calcium compounds (such as gypsum), and a field assessmenr of rhe effects of rhese compounds on water qualiry is the direction rhar future research shou ld rake.

Acknowledgments The aurhors thank rhe staff at rhe EWS Scare Water Laborarory, Adelaide, in particular Mr Evangelo Corsaris, and rhe sraff of the Departm enr of Soil Science, Waire Campus, The Universiry of Adelaide, for rhei r advice and support. The financial support of rhe Aus rra li an Ce ntre for Warer Quality Research is also gratefull y acknowledged.

References AWRC (1991). Freshwater Algal Blooms. Occasional Paper o. 3 prepared by D.A. Steffensen, M.D. Burch and P.D. Baker for Water Resou rces Management Committee , Australian Water Resources Counci l.

Creagh, C. (1992), What can be done about toxic algal blooms.'

Ecos, 72: 14- 19.

Malcolm, R.L. (1985). Geochem isrry of stream fulvi c and humic substances, In Humic Substances in Soil, Sed iment and Water , eds. Aiken. G.R. , McKnight, D.M ., Wershaw, R.L. and MacCarrhy, P: 181-209. Qohn Wiley and Sons).

1 elson, P.N., Cotsaris , E., Oades , J.M. and Bursill, D.B. ( I 990). Influence of Soil Clay Content on Di ssolved Organic Matter in Stream Waters. Aust. J. Mar. Pre.<h1/>aler Res., 4 l : 76 1-774 .

Nelson, P.N. , Cotsatis, E. and Oades, J .M. 0990). Why is some of our water so coloured? W,1ter, 17: 38-39.

Nelson, P.N., Baldock, J .A. and Oades, J.M. (1993). Concenrrarion :ind composition of dissolved organic carbon in streams in relation ro ca tchment soil properties . 'Bio· geochem.. I 9: r -50.

WATER FEBRUARY 1994

400

200

600

80 0

1000

Table 4 Relationship betUJeen t11rbiclity and

(Kondoparinga soil).

Oades, J.M. (1982). Colour and Turbid ity in Water. In "Prediction in Water Quality"'. Proc. of a Symposium on the Prediction in Water Quality sponsored by the Australian Academy of Science and the Institution of Engi neers, Australia, eds. O"Loughlin, E.M. and Cullen, P: 159-179.

(Australian Academy of Science; Canberra).

Skene, T.M. and Oades, J.M.(submitted). The effects of SAR and Electrolyte Concentration on Water Quality: L,boratory Studies. AIISI. j. Soil Res. Stevenson, F.J. (1985). Geochemistry of soil humic substances.

In Humic Substances in Soil, Sediment and Water, eds.

Aiken, G.R ., McKnight, D.M.. Wershaw, R.L. and MacCarth y, P., pp 13-52 (John Wiley and Sons).

Weber, J.H. (1988). Binding and Transport of Meta ls by Humic Materials. In Humic Substances and Their Role in the Environment, eds. F.H. Frimmel and R.F. Christman: 165 -1 - 8. Qohn Wiley and Son Limited).

400

600

1000

Table 5 Relationship between turbidity an Total N (Urrbrae soil).

Authors

Trudi Skene grad11ated from the Universi of Adelaide in 1990 with an Hono11rs degree .

Agrimltural Science, majoring in Soil Science. S, is mrrent ly employed as a Reseaffh Officer in t, Department of Soil Science, The University Adelaide.

Professor Malcolm Oades is a Senior Le lltrer in the Department of Soil Science, The Un versity of Adelaide. He has been involved in mmzber of projects dealing with the role that soi play in determining UJater quality thro11gh t, department's partnership in the Australian Cent for Wiater Quality Researrh.

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800

Average Turbidity (NTU)

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Total

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