Water Quality in the Manning River Estuary Is Made by Determining to What Extend These Long-Term Goals Were Being Met

I ~ I

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I Ii Ii GRE~~TER Ti\REE I II II:1 d CITY COlJNCIL !I I :! I I -'" ... ,,... .. , ... I I I I I I I- I I WATER QUAllIT IN THE MANNING RIVER . I 1989 - 94 I I 1- I I- I I I I I -I ~_ ... ~ __•. .(-."._.,~ ...... -.--=r ,.---' _. I I I I I I I I~ a report prepared by

I Anna Kaliska I SEWER & WASTE SERVICES CRE_ATER TAREE CITY COUNCIL 2 Palteney Street I: TAREE NSW 2430 . Phone (06S) 913 399 I, October 1994 I !::", I I I I I I 1 INTRODUCTION I 2 MONITORING PROGRAM

I 2.1 Stations Location 2.2 Flow Conditions During Sample Collection '1 ····2.3 Parameters-Neasl:<.reci·- . -- .,...... -;:;..:;._._... --. -:::;;....: .. -' I 3 TUE MANNING RIVER SYSTEM 3.1 Catchment Description I 3.2 Tidal Behaviour and Sediment Transport 3.3 Water Resources and the River Flow I 4 TUE SOURCES OF WATER POLLUTION

I 4.1 Point Source Discharges 4.2 Diffuse Source Pollution I I 5 WATER QUALITY IN TUE MANNING RIVER ESTUARY 5.1 Salinity 5.2 Dissolved Oxygen I 5.3 Biochemical Oxygen Demand 5.4 Clarity 5.5 Bacteriological Characteristics I 5.6 Nutrients

I 6 CONCLUSIONS I REFERENCES I I 'I I TABLES 1 1 Water Quality Sampling Stations 2 Manning River Flow at Killawarra Station

I 3 Estimated Manning River Flow at Taree 1 4 Characteristics of Sewage Treatment Plant Effluent I FIGURES I I 1 Location of Sample Collection Sites 2 Tidal Characteristics of the Manning River Estuary

I 3 Load Discharged to the Manning River Before and after Taree Sewage Treatment Plant Flow Diversion

I 4 Salinity - Mean Values 1989-94 1 5 Surface Dissolved Oxygen 1989-94 6 Bottom Dissolved Oxygen 1989-94

I 7 Average Dissolved Oxygen Ratios 1986, I 91/92 and 93/94 8 Biochemical Oxygen Demand 1989-94 I 9 Secchi Disc 1989-94 I 10 Faecal Coliforms 1989-94 11 Faecal Coliform 1989/92 and 93/94

I 12 Total Phosphorus 1989-94 ,-'Jo I, 1,3 Total Nitrogen 1989-94 14 Total Phosphorus 1984-94

15 Total Nitrogen 1984-94

= I I 1 1 INTRODUCTION

I The Manning River system is one of the major river systems in New South Wales and is seen as an important natural resource on a local, regional and state level. The region offers an attractive living conditions with the wide 1 range of aquatic recreational opportunities. Rapid expansion of tourist industry has been observed alongside with the traditional activities as I dairying, beef cattle and fishing. This report attempts to evaluate water quality in the estuary section of the Manning River and is a continuation of previous studies conducted by the I Environment Protection Authority in 1986 and Council in 1988. Since these studies were done, the pattern of human generated pollution discharge to the river has changed. On the one hand two high strength industrial discharges I were removed from the river, but on the other progressing urban development has generated increased amount of stormwater runoff.

1- -.. . ·For·the ~rs-~ of this report the water quality of a waterbody.is defll~d~ a-_ measure of water suitability for particular users uses of the waterbody. Existing scientifically based criteria were used to develop water quality I objectives which represent the desirable, long-term goals of a water quality. Evaluation of the water quality in the Manning River estuary is made by determining to what extend these long-term goals were being met. The water quality objectives for the Manning River estuary are adopted from Australian I or overseas standards for each parameter measured. I 2 MONITORING PROGRAM Water quality data in the tidal section of the Manning River was obtained as a I result of Greater Taree City Council "River Monitoring Program". 2.1 Stations location

I Water quality information was collected at 7 sampling locations in the middle to upper estuary, between downstream Dumaresq Island and just upstream of Wingham. Site selection was based upon land use and geographical criteria I ensuring all major impacts generated by land use activities, discharge location and major tributary inflows were included. Figure 1 shows location of sample collection sites together with sewage treatment plants discharge I points. The detail description of sample site locations is given in the table below. Table 1 I Water Quality Sampling Stations

I Distance Station Location - (kin) No. I 15· 20 Downstream Dumaresq Island ' . 19- 25 Downstream Dumaresq Island bridge . - 23 40 South side Goat Island 26 48 Pacific Hi~hway brid~e at Taree I 30 49 3 kin upstream Taree •..:.± 41 60 Carpun~hat Peninsula I 44 70 600m downstream Win~ham bridge ! I _~-·_U_i:_._ .. .j ------..". ------.,-

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• Sample Station Inlel &STV

Figure 1 Location of Sample Collection Sites ' I

WATER QUALITY IN THE MANNING RIVER I 1989 - 1994 I rage 2

I At the end of 1992 the additional station was established just below Browns Creek inlet and numbered 42.

I 2.2 Flow Conditions During Sample Collection

Collection of river water quality data was carried out from May 1989 to July I 1994 and involved 17 data collection surveys with 1992-94 collections made regularly every 2 months. I As the program was primarily design to assess an impact of point source discharges, most surveys were conducted during medium and low flow in the ·-Rver. Only,ol1_3 .. o.ccaslliilli_lhe.r-i.ller. flow reached its medium_high 9119 .Q.l1.CE::.. _,." I . high VaTue; wnit.:ljoccurred during early 1989-92 stage of the stu~y perioEh'c ;,,--, Dates of sample collection with the river flow at Killawarra Station I (Department of Water Resources 1994) are presented below:

Table 2 I Mannjng J1jver Flow at JfjJJawarra Statjon I Date Flow (MI/day) 10/5/89 13020 28/11/90 849 I 27/2/91 453 14/8/91 546 29/4/92 2839 I 30/6/92 3690 26/8/92 586 28/10/92 328 I 16/12/92 4581 24/2/93 1191 5/5/93 682 I 30/6/93 691 29/9/93 632 30/11/93 761 I 2/2/94 305 12/4/94 787 I 5/7/94 681 I 2.3 Parameters Measured In-field measurements included temperature, salinity, dissolved oxygen, I, Secchi disc and depth. The measurements of temperature, dissolved oxygen i and salinity were taken at depths of 0.1 m, 0.5 m and the bottom.

Greater Taree City Council October 1994 I

WATER QUALITY IN THE MANNING RIVER I 1989· 1994 Fage3 I

The surface water samples were collected at each site and tested by ALS I Tradetest laboratory for biochemical oxygen demand, suspended solids, ammonia, total Keldjahl nitrogen, nitrate, nitrite, filterable reactive I phosphorus, total phosphorus and faecal coliform. In addition the collection of sewage treatment plants effluent samples was undertaken at each day of the river survey. The samples were tested by the I Laboratory for the same parameters as the river samples. I 3 THE MANNING RIVER SYSTEM " •.3.1 .--'.~'--- -'-~- --=::;.:- :'." ---. ."-- -- I The Manning River has a total catchment area of approximately 8400 square kill rising in the Mount Royal range at an elevation of 1000 to 1350 metres above sea leveL The majority of the catchment is hilly to mountainous with I only 10 per cent of the catchment area could be considered reasonably flat (Laurie 1980).

I The most important upper tributaries are the Barnard, Nowendoc, Gloucester and Barrington Rivers, and Dingo and Cedar Party Creek. Below Mount George the valley broadens out, finally developing into a wide flood plain below I Taree. The lower estuary system is complex as the river forms a meandering network of narrow channels. The major tributaries in the lover catchment include Browns and Cattai Creeks, and the Dawson and Lansdowne Rivers. I The river has a permanent entrance to the ocean at Harrington and an intermittent opening at Old Bar.

I Geologically the Manning River estuary can be classified as MatUre Age Barrier Estuary. This type of estuary can be created by extensive river systems with I relatively high sediment loads. During periods of sea level rise along the NSW coast large quantities of marine sand were transported landward and distinctive sand barriers were I formulated. Landward of these barriers estuaries were created in form of broad tidal lakes connected to the ocean by narrow tidal inlets through the I barrier (Estuary Management Manual, 1992). The high sediment loads have in filled the initial back-barrier lake with alluvium, formulating a complex system of sinuous river channels discharging I directly into the ocean through shallow entrance. I ·3.2 Tidal Behaviour and Sediment Transport The movement of water in and out of an estuary is typically dominated by the tides, except during times of flood. Tidal characteristic depend of estuary I shape, and as such the Manning River estuary is classified as Tidal River (Estuary Management Manual, 1992). I .. Greater Taree City Council october 1994 I I

WATER QUALITY IN THE MANNING RIVER I 1989 - 1994 Fage4

The tidal range is elevated in upstream reaches of the Manning River estuary as a result of resonance effects. The nature of such effects is complex and I dictated by the depth and length of the main channel in relation to the frequency of the ocean tide. After initial elevation, tidal range decrease slowly seawards and shows a significant reduction as a result of tidal energy loses at I the heavily shoaled entrance. Figure 2 shows the profile of tidal characteristic of the Manning River (Estuary Management Manual, 1992). I At manning Point - 3 kIn upstream from the entrance, the tidal range is 50% of the ocean value. At Wingham, near the tidal limit and 45 kIn upstream from.the.ri\(eLmo.ul:.b~J.he_tidaLrange is elevated to about 70%,".QLtb.~.o~~<3,.n __ ...:... I "" value.. Such __-tJ.daJ--_ch.?racteristics can influence greatly." the._Jrans.p()I:t.-=-9i~ __ suspended and dissolved matter along the river and determine the pattern of pollution retention and flushing along the study area.

I Typically the rise of the tide is faster than its fall. In consequence, peak flood tide velocities are greater than peak ebb tide velocities. These result in a net upstream movement of sediment. Waves breaking on the entrance bar bring I into suspension large volumes of sediment that can be carried into the . estuary on the flood tide.

I During large floods huge quantity of sediments is transported downstream and the substantial scouring of shallow sand shoals in lower estuarine reaches occur. After the flood dissipates the transported sediments is I accumulated on the seaward face of the entrance and reworked by the action of waves and currents along the beaches.

I 3.3 Water Resources and the River Flow

Rainfall in the catchment area is seasonal with estimated falls occurring I between December and April with average of 1840 mm in the coastal region and 600 mm in the upper catchment (GTCC, 88).

I Yearly rainfall figures at Taree during the study period are listed below (Radio Station 2RE):

I 1991 700mm 1992 991 1993 881 mm I 1994 298 mm - January to May

Greater Taree City Council October 1994 I I I I I ® @@ I I MEAN HIGH WA TER +O.7m I - ./ ~ ~ HALF TIDE LEVEL ...... MSL I i\ MEAN LOW WATER ...... _ -" ~.~.~.'-'--"'" , -----... ---..., .. .' ".- , ...... - . .¥.-=...., -.:- -::--,. .-- ...... 1\' .... O.7m·-~ "'- ~- -- I • • I I • 50 40 30 20 10 o I Distance Along the Estuary (km) I I I I I I I I

I Figure 2 Tidal Characteristics of a Tidal River (Manning Rived

I" I I I .- WATER QUALITY IN THE MANNING RIVER I 1989 - 1994 I Fage5

I The estimated flows for the river at Taree are listed in the table below.

Table 3 I Estimated Manning River Flows at Taree

I Percentage of Time Approximate Flow Equalled or exceeded MIlday

I 50 2204 80 I 677 .:."'.~~:~.- .... ~-~. -~(j~~ - -...... ~ ~ ,~ ...... , _ .. ::." I -399 .. ~'. ...--.- ... ,.-.~: . . . r O ' • .. .-...--::-' _.-., -- I 95 I 255

I The expected water quality pattern will depend on the river flow regimes. Sinclair Knight & Partners (1982) recognised three conditions of river flow:

I Prolonged dry weather - low net flow in the river - greater tidal influence in estuarine section I minimal surface runoff with ground water as a main source of freshwater inflow.

I The period during and immediately following moderate to heavy rainfall - the river is almost fresh from surface to bottom I - high surface run-off with considerable sediment transport towards the sea

I The gradual return of the river to its dry weather conditions - gradual reduction of net flows in the river I - gradual increases in the salinity. Other flow conditions include drought where freshwater inflows are drastically low, and flood where extreme surface flows result in river banks being I' breached and excessive amount of sediment flushed into the sea. I 4 THE SOURCES OF WATER POLLUTION The greatest intensity of land use and urban development of the Manning River Valley is mainly concentrated in the Lower Valley below Wingham and I most discharges are located in this area. It is the area where this study is based: Pollutant enter the river as point source discharges, such as sewage I effluent or as diffuse source pollutants, such as urban stormwater runoff.

I';;:, Greater Taree City Council October 1994 I I

I WATER QUALITY IN THE MANNING RIVER 1989· 1994 I Fage6 I 4.1 Point Source Discharges The effect of point source pollution on water quality depend on the nature of the pollutant, its volume and concentration, and the assimilating capacity of I the water body.

Three sewage treatment works are licensed by the Environment Protection I Authority to discharge secondary treated wastewaters to the river and its tributaries.

I Wingham Sewage Treatment Plant - serves the town of Wingham and was constructed in early 60's to serve the population of 3200 people. Wastewater • -'was-treated-tt31r1!r" low rate trickling filters, secondary ·sedim.entati0l!'-a.l"zd-.~· I . ·-ponding;· In -ei>.j"ly-~9G'·s the plant undergone a-major upgrading wl+kt: -'-' increased capacity of treated works to 7100 people. At the end of 1992 the augmented plant started its operation with secondary treatment extended by I addition of activated sludge process. Secondary effluent is ponded and ultra - violet disinfection applied prior to discharge to the Manning River I immediately downstream of Wingham. Taree Sewage Treatment Plant - serves part of Taree 16500 population. The plant provides secondary treatment by low rate trickling filters and I disinfection by ponding prior to discharge to Browns Creek.. AJthough the plant complied with the EPA licence requirements its effluent contributed to poor water quality in Browns Creek. In March 1994 Taree plant effluent was I diverted to Dawson Sewage Treatment Plant for further treatment. Since then Taree plant works as a pretreatment plant with no dry weather discharges into Browns Creek.

I Dawson Sewage Treatment plant - serves the reminder of the Taree population. The plant provides secondary treatment and some nutrient removal by a continuous activated sludge process in the extended aeration I mode. Effluent is disinfected by ponding and then pumped to the Manning River between Taree and Cundletown.

I The results of a survey of effluent quality for each sewage treatment plant, summarised in terms of concentrations and loadings, are shown in Table 4. Parameters listed are .. the mean values for the study period. Separate I calculation were done for the period before and after Taree Treatment Plant - flow diversion to Dawson Plant. The total load of point source discharges in term of biochemical oxygen demand, suspended solids, total nitrogen and I total phosphorus is presented at figure 3. The graph shows reduction of total load of discharge achieved, particularly in term of total nitrogen. Dawson I plant, .as a more modem than Taree plant removes nitrogen more effectively. The diversion of effluent took place at the end of the study period and not enough data has been collected since to evaluate its effect. It is expected that I reduction in total load of discharge and change in location of discharge point will improve water quality in the river in vicinity of Taree agglomeration with Browns Creek as a main beneficiary.

I-~. ; Greater Taree City Council October 1994 I I I Table 4

Quality of effluent discharged to the Manning River I May 1989 -March 1994 TP TN Source Flow BOD SS Faecal Cliform KLiday mg/l mg/l mgll mg/l organisms/100ml I 17.1 Wingham STP 1000 3 8.3 10.8 606 9.2 22.6 Taree STP 2200 12.9 30 1133 5.3 I Dawson STP 3100 6.4 17.6 7.4 783 I

Quality of efiiuent affer'Tafee STP flow diversion .- .... : ----

Source Flow BOD SS TP TN Faecal Cliform KLiday mg/l mg/l mgll mg/l organisms/100ml Wingham STP 1000 6 9 15.7 18 15 I Dawson STP 5200 9 22 7.2 6.3 1080 I

I Load discharged to the Manning River May 1989 -March 1994 I Source Mean Pollutant Loads kg/day BOD SS TP TN I Wingham STP 3.0 8.3 10.8 17.1 Taree STP 28.4 66.0 20.2 49.7 Dawson STP 19.8 54.6 22.9 16.4 I Total 51.2 128.9 54.0 83.3

I Load discharged after Taree STP flow diversion

I Source Mean Pollutant Loads kg/day BOD SS TP TN I Wingham STp· 6.0 9.0 15.7 18.0 Dawson STP 46.8 114.4 37.4 32.8 I Total 52.8 123.4 53.1 50.8 I I I I o za.enO f-f-enm I !!:I 0 t:l t:l I I ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• -o 'iii... I Q) > "0 "'"o 3: c I o -Q) III ;: C1> ~~ •,::::.~ , --_. <-,:~.,,~. , .... :_._ ... ~-. '-- '''I '(,f) Q) ...Q) CO I-... I Q) .... -CO "0 I -CO C"l e III .£ I :: Q) ,-o,.::J... u.. III ,~ a: I 0) - - I C'C ~ c III o .- III ; ~ C1> I o .~ "0 - "~ III o 0)... :;::: C'C C1> I .::. ~ u o C1> f,f) -m .,.~ "0 "0 I oC'C ...J I I

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WATER QUALITY IN THE MANNING RIVER I 1989 - 1994 I Fage7

I 4.2 Diffuse Source Pollution

Diffuse pollution, which can be both urban and ruraL arises from many I diverse land use activities. The most important source of diffuse pollution of concern to water quality is stormwater runoff from urban areas. According to Environment Protection Authority (1989), urban runoff has become the major I source of pollution to waterways around the towns and cities of New South Wales and is now the most important determinant of receiving water quality in I these areas. Urban development creates impermeable surfaces, such as pavements, roads -_ .... - _-:- -and .. r.oof.s ...... whk.h _increase the speed and_~volume .. of_.storm.wab<;.r~'oI:U1'lOf-f.. - •. ~I Sto[l11w~ter .runofLfrQm. urban areas contains various .pollutants, .such as-=-,_. litter, animal wastes, vegetation, oil and grease, metals, bacteria, nutrients, pesticides, noxious weeds and seeds, and massive quantity of sediments.

I Rural runoff is increased as a result of the clearing of vegetation from the catchment which contribute substantially to the silt loads of waterways. Rural runoff contain agricultural chemicals (herbicides, pesticides), and is a I significant source of nutrients. I 5 WATER QUALlTY IN THE MANNING RIVER ESTUARY The interpretation of water quality in the Manning River estuary is based on land use activities and the location of discharges. As all parameters show a I significant variability, mean values and 70 percentile values were obtained and plotted graphically to show any variations along the studied section of the I estuary. 5.1 Salinity

I Data collected from in-field measurement of salinity show that the Manning River along the study area is a partially mixed type of estuary. The salinity varies continuously through the depth of the water column with bottom I concentrations higher than surface. Figure 4 shows mean surface and mean bottom salinity concentrations. The plot indicates that increased bottom to surface stratification exist at all stations near Taree (stations 48,49,40). Such I conditions are typical for low tidal velocities which are insufficient to cause significant vertical mixing. The Environment Protection Authority Study (1986) recognised that for the partially mixed system there is a potential for retention I of contaminants.

Increased vertical gradient of salinity existing at all stations around Taree I indicates that this section of the river has lower tidal velocities and increased potential for retention of pollutants in comparison with the other sections of I the river. J I .~ Greater Taree City Council October 1994 I _11.._ .. __ __. ______,._

, -.I Figure 4 Salinity - Mean Values 1989-94 i'!

30 I~':~'.~•••••••••.•••.••• ~ ••••••••••••••.•.~II~ ••••••••••.•••.• 25

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II 10 I.

WATER QUALITY IN THE MANNING RIVER 1 1989· 1994 PageD I

1 5.2 Dissolved Oxygen Most aquatic life requires oxygen to survive. Aquatic plants, including algae, I are net producers of oxygen during daylight hours, but are net consumers during the night. Because of this, dissolved oxygen levels varies diurnally, with lowest concentrations occurring at sunrise and highest at sunset. As oxygen is used by bacteria and other microorganisms during natural I purification process, the level of dissolved oxygen measurement will indicate the overall condition of the water.

I Oxygen solubility falls as temperature and salinity increases. Because of the _I .... -'-"~" -.. -~( '<;

I, Greater Taree City Council October 1994 I ,.. t -,- _., ,_. ! -. - .- .- '------, -- -- - !

Figure 5 " i Surface Dissolved Oxygen 1989-94 I

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WATER QUALITY IN THE MANNING RIVER I 1989· 1994 I Page 9

I Such location of mean dissolved oxygen levels depression can be justified by certain tidal characteristic. As peak flood tide velocities are greater than peak ebb tide velocities, a tendency for greater upstream movement of water on I the flood tide compared to downstream movement on the ebb tide occur. The phenomenon is referred to as "tidal pumping" (Estuary Management Manual 1992). These can cause retention of organic particles upstream of I discharge points. The lowest 70 percentile value of dissolved oxygen was calculated for the I station 42 by Browns Creek inlet with 70% of all bottom measurements being above 57%. Despite of depletion around Taree, the results for all locations __ ~ncti..r,:at~ dissolved oxygen level of saturation better than the limit levels recommended fo;- fish he

To evaluate changes in dissolved oxygen pattern for a longer period of time, the ratio of mean bottom dissolved oxygen to mean surface dissolved oxygen was calculated for each station and plotted together with dissolved oxygen ratios obtained from the surveys done by the Environment Protection Authority in 1986. Figure 7 shows the graphical representation of dissolved oxygen ratios for 1986, 91/92 and 93/94.

In comparison to the results measured in 1984-86 the depreSSion in bottom I dissolved oxygen at Taree area has been significantly reduced. This improvement in dissolved oxygen regime has been attributed to removal of high strength industrial discharges from the Manning River, which took place I in 1989. The difference in the shape of 91/92 and 93/94 curves is probably due to different flow conditions experienced during collection of samples, with higher river flows occurring during earlier study period and consistently I low flow conditions during 1993/94 surveys. Dissolved oxygen depression was shifted from station 48 further upstream to station 49 during this period. The moderate improvement in dissolved oxygen regime during last two years I can be noticed downstream of Pacific Highway bridge (station 48). I 5.3 Biochemical Oxygen Demand Biochemical Oxygen Demand (BOD) is a measure of the level of organic material present in the water. It is a measure of the amount of oxygen that I will be consumed from the water mass within a given period of time (standard method recommends 5 days) when the existing bacterial populations break down the organic matter. I, Overseas standards for marine and estuarine waters recommend the BOD results to be below 2.5 mg/l in case the US standards, or below 4 mg/l in I case pf European standards (Australian Water Resources Council 1982). No Australian standards has been established for BOD. I The variation in BOD values are presented in Figure 8. The mean BOD fluctuates along the river from 2.4 mg/l upstream of Wingham (station 70) to I 2.7 mg/I by the Browns Creek inlet (station 42). Greater Taree City Council October 1994 I -.-.- ..- .. ------.. ------..-

Figure 8 i Biochemical Oxygen Demand 1989-94 'j 3

2.5 .'

~ 1.5·

0.5 .

o R20 R25 R40 R42 1148 R49 1160 R70 Stations I

I WATER QUALITY IN THE MANNING RIVER 1989· 1994 I Fage 10 I 70 % of all readings along the study area were below 2 mg/! which indicates I good water quality during majority of sampling days. However, occasionally at the stations adjacent to Taree agglomeration the BOD readings were elevated I as high as 4-6 mg/!. 5.4 Clarity I Secchi disc readings were analysed to evaluate clarity of surface water. Secchi disc measurement is done by lowering a standard black and white disc '1 ~_._-,-15~.cchi disc) into the water~~d measuring the ?~pth at whic~ it can no ~,?nger be seen. Such measurements reflects·the-turbldlt~t:·~tel.-Le .. the ability of water to transmttlight: '=~'~~"-" ... ,.

Secchi disc readings will reflect the sediment transport pattern within the I estuary, particularly muds transport regime. Turbidity of the river water increases after rain with noticeable urban runoff effect.

I Mean and 70 percentile values of Secchi disc measurements are shown in Figure 9. Secchi disc readings were found to vary from 0.5 m to 4 m with mean values along the river being between 1,7 m and 2.25 m. Average value I for Secchi disc measurements was 1.8 m above Wingham with clarity improvement to above 2 m downstream of station 60 (1.5 km downstream Wingham) to station 48 (Pacific Highway bridge). Such improvement in water I clarity can occur as a result of flocculation and sedimentation of colloidal clay particles during mixing of fresh water with seawater which decreased the I concentration of suspended sediments. The clarity of river water reaches its minimum at station 42 which is located I by Browns Creek inlet. The creek collects the majority of Taree urban runoff. 5.5 Bacteriological characteristics

I Disease causing microorganisms enter waterbodies via sewage discharges and urban runoff. Levels of Faecal Colliform bacteria is used as an indicator of faecal contamination. This is an indirect measure of the possible presence I of waterborne hum9-n pathogens.

Water quality requirements for primary contact recreation, including I swimming, recommend Faecal Co Ii forms levels to be below 150 on average (Water quality Criteria for NSW 1990).

I The 'plot of mean and 70 percentile surface Faecal Coliforms levels is presented in Figure 10. Figure 11 shows Changes in Faecal Coliforms levels 1'1 between 1989/92 and 93/94. , fi .j lei, Greater Taree City Council october 1994 I I

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Figure 10 '. Faecal Ciliform in the Manning River 1989-94i 140 I...... ,

100

-180 E o o ..- ~ Mean Fec Col Vi E --+-70 Percentile .!!l160 c: e', '"o·

o I,······ .j ....•.•.•.•.·1·····;·;·· f·········t··········· -} .. ;.;.;.;.j ..... ;... /;.;.;.;.;.; .., ...... j...... 1;.;.;.;.;.;.;j' ...... j...... t-;.;.;.;.;.;l ...... ·1········ '1· ...... ,...... ·1··;······.,.··········; ·j··········r········· t-·;·········1········· \

R20 R25 R40 R42 R48 R49 R60 R70 Stations _:._L_L_. ______.. ____ ._. __ .... _

Figure 11 Faecal Coliform 1989/92 &93194

200 \.' ...... '.' . .'.'.'.'.'.'.'.'.'.' .. .' .. .'.' .. .'.' ...... ' . .'.'.'.'.'.'.'.'.'.'.' ...... '.'.'.' ...... '.'.'.'.'.' ...... '.'.'.'.'.'.'. .'.'.'.'.'.'.'.'.'.'. ..J

180

160

140

-+-89/92 --93/94

~ 60

R20 R25 R40 R48 R49 R60 R70 Stations

., I WATER QUALITY IN THE MANNING RIVER I 1989· 1994 Page 11 I

On average Faecal Colifonns levels was below 115 organisms per 100 ml for I all stations along the study area with maximum shifted from station 60 downstream of Wingham treatment plant discharge point in 1989/92 to station 42 by the mouth of Browns Creek in 1993/94. Substantial reduction I in mean Faecal CoJifonns levels downstream of Wingham occurred as a result of the treatment plant augmentation in 1992 with provision of ultra - violet disinfection. Plot in Figure 10 indicates the impact of both Taree and I Wingham agglomeration on Faecal Colifonns pattern.

Significant increase in Faecal CoJifonns levels regularly occurred following I heavy to moderate rainfall, with average results elevated to 190 - 350 organisms per 100 ml depending on location.

... -,. "I Figure 11 shows a substantial reduction in Faecal Colifonns levels between two compared periods of time. This can be attributed to the fact that higher I flows were observed in the earlier period of study. 5.6 Nutrients

I Plant growth requires many different types of nutrient. Nitrogen and phosphorus are the main nutrient detennining growth of aquatic plant. If nitrogen and phosphorus are present in water in excessive levels, they can I promote the uncontrolled growth of phytoplangton, referred to as "algal bloom". Apart of affecting aesthetics of the water, excessive algal growth can deplete the level of dissolved oxygen present in the river water which leads to I fish kills.

Increased nutrient levels in river water originate mostly from the discharge of I treated effluent and from urban and rural runoff. The inefficient use of fertilisers can result in high nutrients levels in rural runoff. According to McLusky (1989), the major source of nitrogen and phosphorus is due to I drainage from the fertilisers used in agriculture. Estimation were made that less than half of the fertiliser applied becomes bound into the harvested crop, and the reminder is lost through infiltration into rivers. Nitrogen and I phosphorus are subject to constant changes in their fonn in estuarine environment after entering the biological cycle.

The recommended limit values for total nitrogen and total phosphorus are set I to prevent excessive algal growth. The acceptable level of total phosphorus in receiving waters has been given as 0.1 mg/l for flowing streams in the US, but I Hurt (1974) has noted that the relevance to Australian conditions is largely unknown. "Water Quality Criteria for NSW" 1990 (Discussion Paper) gives the acceptable level of 0.05 mg/l for phosphorus and 0.5 mg/l for nitrogen. As seawa.ter contains 0.035 mg/l of phosphorus and 0.25 mg/I of nitrogen I (Estuary Management Manual 1992), the recommended values of 0.05 mg/I and 0.5 mg/I for each nutrient respectively do not allow to accommodate any significant quantity of nitrogen or phosphorus generated through human , activity.

I.~ Greater Taree City Council October 1994 I _... , -. - .. - -. ------. ------;-

Figure 12 Total Phosphorus 1989-94

0.12

0.1

0.08

c:::::::m Mean T P 0.06 1 ~ --70 Percentile l----.~~.--.,.--.- --< •.

0.04

o --,- R20 R25 R40 R42 R48 R49 R60 R70 Stations _,." .. _, _I. _, ______.. __

Figure 13 Total Nitrogen 1989-94

0.7

0.6 .

0'.5

0.4 ::::: ------J OJ E ~;~:r:~ntile...•....." ~='----'-"--'---" ._._ 0.3

0.2

0.1

o R20 R25 R40 R42 R48 R49 R60 R70 Stations _L.,._I:_;: _, .. • ....• -... ------.. -- I -.-

Figure 14 Total Phosphorus 1984-94

0.09 1.:.:.:.: ...... ·...... :... '.'.' .."".'.'.'.'.'·.· ...... ' .. '.'.'.'.'.'.'.'A· ., ...... ' ... .' .. .'.'.'.' .. .'.'.'.' ...... '.. '...... ' ...... '.'.'.'.' . .'.'.'.'.'.'.' ...... '.'.'.'.' . .'.'.'.'.'.'.'.'.'.' ...... ,

0.08

0.07

0.06

0.05 -+-TP 84/86 --TP 86/88 -.to- TP 89/92 Ig10.04 -&-TP 93/94

0.03

0.02

0.01

o , ...... ··················f······· ...... "( ...... j...... ·······{ .. ···· ...... ···· .... ······ ...... ···· .. ···· .. l ...... ·· ...... ~ R20 R25 R40 R48 R49 R60 R70 Stations _ •.. ,.,_1.. '_"";'." _ ... _ ... _ .. _ •.•. __ ... _ .. _ ,_

Figure 15 Total Nitrogen 1984-94

0.7 I'.'.'.'.'.'.'.'.'.'.'.'.'.' ... .' .. .'.'.'.'.'.'.'.' .... .' .. .'.'.' . .'.'.'.'.'.' . .' . .'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.' ...... '.'.'.'.'.'.'.' .... .' . .'.'.'.'.' .. .'.'.'.' ...... '.'.'.'.'.'.'.'.' ...... ' . .'.'.'.'...... '.. .'.'.".".'1

0.6

0.5

-+-TN 84/86 -+-TN 86/88 ---IIr- TN 89/92 'a.1 0.3 --TN 93/94 E

0.2

0.1

o 1··················································1'·················································1'························ ...... 1' ...... 1' ...... ;...... 1' ..... ;.;.;.;.;.;.;.;.;.;.;.;.;.:.:.:.:.:.:.:.:. :\ R20 R25 R40 R48 R49 R60 R70 Stations I

I WATER QUALITY IN THE MANNING RIVER 1989 - 1994 I rage 12

I According to "Australian Water Quality Guidelines" (1992) it is impossible to recommend a single set of nitrogen and phosphorus concentrations that will prevent phytoplankton problems in estuarine waters in Australia. Site-specific I studies should be undertaken to determine appropriate concentrations for each particular system.

I Mean and 70 percentile total nitrogen and total phosphorus values are presented in Figure 12 and 13. Mean total phosphorus concentrations was found to vary between 0.05-0.06 mg/! in the upper section of the Manning I River estuary around Wingham down to station 48 by Pacific Highway bridge, and between 0.06- 0.09 mg/l at the section of the river adjacent to Taree and 1". __ , downstream of Taree. - - - The impact of sewage treatment plants effluent discharge was evident. Slightly elevated phosphorus level at station 60 downstream of Wingham I plant, and Significant increase of phosphorus concentration at station 42 by Browns Creek and station 25 downstream of Dawson plant discharge point were observed. 70 percentile curve for total phosphorus shows highly I elevated value of 0.12 mg/l at station 42. Generally the recommended phosphorus level of 0.05 mg/! was frequently exceeded at all stations along the study area.

Mean total nitrogen levels were found to vary between 0.3 mg/! and 0.46 mg/! along the study area. Mean concentrations of total nitrogen at all stations were below the recommended value of 0.5 mg/! with maximum levels at station 42 by the inlet of Browns Creek with 70 % of all samples showing total nitrogen level below 0.6 mg/!.

To determine the trend in total phosphorus and total nitrogen levels over the longer period of time, mean values of nutrients concentrations obtained from I the previous studies done in 1986 and 1988 are plotted in figure 14 and 15 together with the present study results.

Mean total phosphorus distribution along the study area shows the same I pattern during last 10 years. The highest levels were observed around Taree with downstream reduction in total phosphorus concentration at station 20 (downstream of Dumaresq Island). Elevated values were measured I downstream of Wingham with reduction in total phosphorus concentration at station 48 (Pacific Highway bridge). The graph indicates that surveys done in 1986 and 1988 found lower total phosphorus levels that the present study. I Total nitrogen distribution over last 10 years was less regular but also indicates an increase in total nitrogen distribution during 10 years time.

I 6 CO,NCLUSIONS

During the period of this study covering 1989-94, the water quality in the Manning River estuary was found to be suitable for present beneficial uses of the river. It is difficult to evaluate if the level of total phosphorus found in the river have a potential to cause a nuisance algal growth.

Greater Taree City Council october 1994 I ,, WATER QUALITY IN THE MANNING RIVER I 1989 - 1994 I rage 13

I Threshold concentration for total phosphorus present in Australian estuarine waters above which algal growth could be expected is not known. The site specific study has to be undertaken to determine appropriate concentration I for the estuary section of the Manning River.

Water quality varies along the study area. The best test results were obtained I in upper estuary upstream and downstream of Wingham. The section of the river adjacent to Taree showed relatively poorer water quality with improvement downstream of Dumaresq Island. Such distribution of water quality characteristics result from combined effects of the discharge pattern and river hydrological characteristics .

.J:he,criver .5~rJjg.n.ground Taree area was affected by two sewage treatment plants diSCharges and urban stormwater runoff. The uppe-r:"part of~[.r:dy I received Wingham stormwater runoff and treatment plant effluent. Attention has to be drawn to the Manning River estuary hydrogeological characteristics. As a Mature Age Barrier estuary with associated Tidal River type tidal characteristic, the Manning River estuary exhibits poor ability to I assimilate pollution.

Unlike other major North Coast rivers, the Manning River estuary is a partially I mixed system. Vertical salinity gradient indicate low tidal velocities, insufficient to cause substantial flushing.

I Tidal characteristics are more favourable at the upper estuary near Wingham, where tidal amplitude is elevated by the occurrence of tidal resonance. This might be a reason why Wingham agglomeration was found to have no I significant impact on the water quality in the adjacent section of the river.

Increased salinity gradient observed in the river around Taree indicates that I this section of the river has lower tidal velocities and poorer mixing with comparison to other sections along the river. Such feature of tidal flow can create a potential for retention of contaminants. In addition major point and I diffuse source discharges are located in this area.

This highly undesirable pattern of pollution discharge is expected to show 'I noticeable improvement after Taree Treatment Plant effluent was diverted to Dawson plan for further treatment. Since March 1994 Taree plant works as the pretreatment plant with no dry weather discharges into Browns Creek. The I effluent diversion reduced the load of discharge and improved a location of major discharges around Taree. Dawson Treatment plant discharge point is I locatec:t by the Goat Island downstream of the main urban area of Taree. The load of point source discharge have been significantly reduced over the years since the first study on water quality in the Manning River estuary was conducted in 1986. High strength industrial discharges were removed from the river in 1989. Taree Treatment Plant effluent improved significantly after the commissioning of Dawson Treatment Plant in 1986.

Greater Taree City Council october 1994 WATER QUALITY IN TI1E MANNING RIVER 1989· 1994 Fage 14

Wingham Treatment Plant improved its effluent quality after augmentation in 1992. The observed effects of these improvements in quality of discharge I, seems to be below expectations. Moderate improvement can be noticed in bottom dissolved oxygen level near Taree, but nutrients concentration along the study area showed significant increase.

I These facts point towards urban runoff as a major determinant of receiving water quality in urban areas, which support the Environment Protection I Authority opinion(l989) quoted in Chapter 4.2 of this report. As the Manning River charact.er-st.ics make the river sensitive for pollution discharge, the systern has tei"S.;'; 't5nstantly monitored. More attention during I _ themorutortrrgprogram should be given to phytoplangton_.growthme2m,.,~ it=-· order to control the potential for nuisance algal bloom. Future studies will evaluate the results of Taree treatment plant flow diversion to Dawson plant. I The future management efforts has to be focused on control and possible ,I reduction of urban stormwater discharge into the river. I

I +++++++++++++++ I I' I 'I 'I I

I , I ,-& I Greater Taree City Council october 1994 ; I. ---'-'-~--' ....

I WATER QUALITY IN THE MANNING RIVER 1989· 1994 I rage /5 I I REFERENCES

I' Australian and New Zealand Environment and Conservation CounciL 1992, Australian Water Quality Guidelines for Fresh and Marine I Waters. Australian Water Resources CounciL 1982, The ~cology of a polluted urban Creek. -Ausn"alian. Govel:r;ment Publishing Service, I Ca!O.Derra. .-.. "_.

Bird, E.C.F., 1984, Coast. An Introduction to Coastal I Geomorphology. Australian National University Press.

Kennish, M.J., 1986, uology of ~stuaries: Physical and Chemical I Aspects. CRC Press, Boca Raton Florida. I Laurie, Montgomerie & Pettit pty. Ltd., 1980, I'few South Wales Coastal Rivers. rIood Plain Management Studies. Manning Valley.

I McLusky D.S., 1989, The ~stuarine uosystem. Blackie.

Sammut, J., 1994, Impacts of Poor Water Quality on Fish. I Geomorphology and River Health in NSW Conference, Macquarie University, Sydney

I' Sinclair Knight & Partners, Laxton, 1.S.& J.H., 1982, Evaluation of the Effects of Effluent Discharge From the Dawson Sewage I Treatment Works on the Receiving Waters. Sinclair Knight & Partners, 1980, Taree Sewerage Augmentation, I Dawson River Works, Review of Environmental Factors. State Pollution Control Commission, 1990, Water Quality Criteria for I I'few South Wales: Discussion Paper.

State Pollution Control Commission, 1989, Pollution Control Manual I' lor Urban Storm water.

State Pollution Control Commission, 1987, I'forthern Rivers Study I I'fo. 7: Water Quality in the Manning River Report. I Greater Taree City Council october 1994

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