1
Bruce ~ate. tal Scienliat Senior EllvUOIIJlIeD E8tullY Management ce State Pollution Control Commission Northern Rivers Study No. 7 Water Quality in the Manning River State Pollution Control Commission Northern Rivers Study No.7 .Water Qual ity in the Manning River
.\, . !, Other titles ID the Northern Rivers Study are:
W.lIer Quality In the Twccd-Terranora Estuary Waler Quality In the Brunswick Rivvr W.lIer Quality In the Clarence RiveT Waler Quality In the Bel/inger and Kalang RiveTS Waler Quality In the Richmond RivCT WaleT Quality In the Mac/cay River Waler Quality In the Hastings River
This report was prepared by Ross Williams, State Pollution Control Commission, Sydney.
The Commission acknowledges the assistance provided by the following in carrying out carrying out this study:
Commonwealth Government funds provided through the Wage Pause and Community Employment Schemes; and
the NSW Water Resources Commission for flow data.
ISBN 0 7305 0710 6 June 1987 CONTENTS
Summary
1 Introduction 1
2 Manning River Study 4
2.1 Objectives 2.2 Program
3 Catchment and River Characteristics 8
3.1 Catchinent Description 8 3.2 Point Source Discharges 8 3.3 Wa ter Resources and River Flow 9
4 Water Quality in the Lower Manning Valley 12
4.1 Manning River 12 4.2 Dawson River 17 4.3 Major Tribut aries of the Manning River 21 4.4 Quality of Effluent Discharged to the Manning River 26
5 Factors Influencing 'Water Quality 30 in the Manning River
5.1 Hydrodynamic Factors 30 5.2 Point Source Discharges 33 5.3 Urban Run-Off 33 " 6 Comparison of Water Quality 34 With Other NSW Waterways
7 Conclusions and Recommendations 36
8 References 38
Appendixes
A Station Locations 39 B Analytical Methods 41 Figures
Northern Rivers Study Catchment' Basins 2
" Location of Sample Collection Sites 6
:; Selected ,Salinity Values for Flow Characterisation 10
:; Secchi, NFR, Tui-bidity and VSS: Manning River 14
(i TP, TN, N:P Ratios and Chlorophyll a: Manriing River 16
7 Soluble Nutrients and Keldjahl Nitrogen: Manning River 18
X Temperature, Salinity, Dissolved Oxygen and pH: 19 Dawson River
<) Secchi, NFR, Turbidity and VSS: Dawson River 20
10 TP, TN, N:P Ratio and Chlorophyll a: Dawsori Rivet 22
1'1 Soluble Nutrients and Keldjahl Nitrogen: Dawson River 23
12 Temperature, Salinity, Dissolved Oxygen and pH: 24 M;ljor Tributaries
U Secchi, NFR, Turbidity aild VSS: Major Tributaries 25 .' 14 TP, TN, N:P Ratio and Chlorophyll a: Major Tributaries 27
15 Soluble Nutrients and Keldjahl Nitrogen: 28 Major Tributaries
16 Variation in Dissolved Oxygen Saturation at Two Depths 31 in the Manning River
17 Schematic Representation of Tidal Moveinent at Two 32. Depths and Locations in the Manning River Tables
Water Quality Sampling Stations Per River Catchment 5
Location of Mainstream Stations: Manning River 5
Location of Stations on Manning River Tributaries 7
4 Discharge Information 8
:; Wilter Quality Subdivisions Based on River Flow 11
Ij Average Nutrient Concentrations for the Manning River 15
7 Average Nutrient Concentrations for the Dawson River 21
Average Nutrient Concentrations for Manning River 26 Tribut aries
() Median Pollutant Concentrations and Approximatl: Loads 29 of Discharges to the Manning River
III Selected Water Quality Characteristics for Low Flows 35 of North Coast Rivers Summary
The State Pollution Control Commission has conducted extensive water quality surveys of several rivers'in the North Coast Region of New South Wales. The program was developed in response to increasing concern from the public and government organisations that point and diffuse sources of pollution were having detrimental impacts on aquatic environments and fisheries resources.
The program involved investigations of all major rivers on the North Coast including the Tweed, Brunswick, Richmond, Clarence, Bellinger, Kalang, Maeieay, Hastings and Manning. The investigations commenced in November 1983 and data were collected until April 1986.
The surface water quality in the Manning River was found to be good in terms of clarity and suspended solids loads during low flows. Phosphorus concentrations were elevated in the river section adjacent to Taree and downstream of Wingham. Although this stimulated algal growth, resulting in an assimilation zone extending for 20 kilometres between Wingham and Taree, it, did not have a significant impact on beneficial uses of the water. Deterioration in water quality although not severe in this zone could be at tributed to effluent discharge from several dairies and. a sewage treatment works near Taree. Wa ter quality at depth, ie over 2 metres, was poor as a result of hydraulic factors, and treated effluent and wastewater disposal st rategies at the time of the investigation; it should however be noted that new strategies are being developed.
Taree was also found to contribute significant pollutants from urban run-off during high flows. This resulted in eleva ted suspended solids and loss of clarity during these flows. Gravel extraction a~d processing upstream of Tarce was also found to influence suspended solids concentrations during low flows.
Browns Creek was so affected by effluent from Taree sewage treatment works that it could not support aquatic life. Odours were also associated with the creek. Other tributaries such as the Dawson River were found to have poor quality due to natural causes. Thus the Dawson is not capable of receiving effluent containing oxygen-demanding wastes or nutrient concentrations in excess of threshold levels. Cattai Creek and the Lansdowne River were found on occasIOns to have poor clarity during low flows but the cause was unknown. t INTRODUCfION
The State Pollution Control Commission has conducted extensive water quality surveys of major rivers in the North Coast Region of New South Wales. The program was developed in response to increasing concern from the public and government organisations that point and diffuse sources of pollution were having detrimental impacts on aquatic environments and fisheries resources.
The region offers an attracti~e lifestyle with ample aquatic recreational facilities and in recent times has experienced major population growth. Rapid expansion in the region has led, in some instances, to overloading of sewage facilities and increased industrial activity and urban run-off. The region also boasts a rapidly developing tourist/holiday industry catering to a wide cross-section of the population. In addition to pressures from an cxpanding population, concern has been expressed about the impact of other land use activities such as:
agricultural practices, In particular the use of pesticides and fertilisers;
soil erosion, both from the land and river banks;
loss of aquatic habitat through wetland reclamation; and
con I rol and ope ra tion of drains and flood mi tiga t ion structures.
It is the Government's and the Commission's desire to ensure water quality problems do not develop as a result of changing land use activities and where problems already exist, that communities, industries and relevant government organisations take appropriate action to ameliorate them. The ohjective is to maintain acceptable standards of water quality, such as dissolved oxygen concentrations and clarity, and to reduce the risk of the devclopment of eutrophic or stratified water .column conditions which could affect the viability of wildlife, recreational and fisheries resources.
The study was partially funded by the Commission's resources and by the Commonwealth Government's Wage Pause and Community Employment (CEP) Programs. This is one of a series of reports summarising the investigations carried out under the Northern Rivers Water Quality Study.
The study program developed by the State Pollution Control Commission involved investigations of all major rivers in the North Coast Region including the Tweed, Brunswick, Richmond, Clarence, Bellinger, Kalang, Macleay, Hastings and Manning. Figure 1 details the range and extent of the clltchment areas studied. The study commenced in November 1983 and data were collected until April 1986. Not all rivers were sampled over this period as the program has been. flexible; as sufficient information was collected on a specific river, some surveys were discontinued and new ones started. The timing and number of surveys conducted were designed to reflect a wide range of river flow conditions.
In addition to the general water quality investigations, specialist programs were carried out into treated sewage disposal strategies for the Tweed Heads-Terranora area (SPCC 1985a and Williams 1986) and work is still being undertaken in the Clarence. This work includes joint investigations with the Department of Agriculture's Divisions of Fisheries and Veterinary Research 2
Tweed Heads
N 6 o 50 • I qo km
1 Tweed River ~>"77:r,.,1"'V Port Macquarie 2 Richmond River 3 Clarence River 4 Bellinger River 5 Macleay River 6 Hastings River 7 Manning River 8 Brunswick River
Figure 1: Northern Rivers Study Catchment Basins 3 into water quality arid its possible relationship with "red spot" fish disease in the Claren(:e River. Funding for the continuation of this program involves a Fisheries Industry Research Account grant.
The overall program involved a total of 242 sample locations along the nine rivers, some from their mouths to their headwaters, others to the tidal limit. Forty-four major licensed point source discharges were sampled under the program. This report details investigations undertaken on the Manning River system. 4
2 MANNING RIVER STUDY
2.1 Ohjectives
The study of the Manning River was designed to:
develop a database on water quality within the catchment based on specific river flow regimes;
assess the impacts of point source discharges and determine the adequacy of licence conditions;
interpret the database in terms of land use activities and the point source discha rges to. identify any wa ter quality problems; and
recommend action where necessary to ensure current or potential water quality problems are minimised.
2.2 Program
The study involved the collection of a series of databa~es that would enable present water quality characteristics to be established. This allowed a review of current land use and effluent disposal strategies to maintain slitisfactory water quality throughout the system in future years. Data collected can be grouped into categories of: background catchment details, land use activities, licensed discharges, rainfall, river flow and water quality characteristics.
Collection of river water quality data was carried out from June 1984 to March 1986 and involved 11 data collection surveys. The survey dates were selected to represent pre-determined flow regimes and were not a fixed interval monitoring program. This flexibility enabled the frequency of silmpling to cover and assess a selected range of flow conditions (see Section 3) over a relatively short period. To characterise water quality, an extensive network of sampling stations was established throughout the Manning system as with all other North Coast rivers studied. Table 1 shows the number of stations established during the study for each of the C,l tchme n ts.
Water quality information for the Manning River was collected at 27 sampling locations between the river mouth and just upstream of Wingham (Figure 2). Site selection was based upon land use and geographical criteria ensuring all maj()r impacts generated by land use activities, discharge locations and major tributary inflows were assessed. Appendix A provides a de tailed descript ion of sample site locations:
In addition to the water quality study, an investigation was conducted jointly with the Public Works Department (Manly Hydraulics Laboratory - Data Collection Section) into the influence of tidal movement on water quality. This study adopted a multi-disciplinary approach which involved the close co-operation of both organisations. The program was designed to provide information to assist in developing effluent disposal strategies which would have minimal impact on the Manning River environment. The three components of the investigation were the use of dye-tracing techniques, and current velocity and water quality measurements. The results of the investigation are presented in the 1987 paper by Williams and Wyllie. 5
Table ·1
Water Ouality Sampling Stations Per River Catchment
Main Trib- Indust- Rivers Stream utaries STW ri al Total
Twced 13 29 3 1 46 Brunswick. 6 3 1 0 10 Richmond 16 14 5 5 40 Clarence 17 20 3 4 44 Bellinger 14 3 1 1 19 Kalang 4 1 1 7 Macleay 11 14 4 7 36 Hastings 5 5 2 2 14 Manning 9 14 2 2 27
242
To assist in the interpretation of later figures, Table 2 gives each mainstream station's location and its distance from the river mouth while Table :.'\ provides similar information for stations on major tributaries.
Table 2
Location of 'Mainstream Stations: Manning River
Distance (km) Station No. Location
5 10 Pelican Point 15 20 Downstream Dumaresq Island 19 25 Downstream Dumaresq Island bridge 21 30 South Passage 23 40 South side Goat Island 26 48 Pacific Highway 30 49 3 km upstream Taree 38 50 . 3 km upstream Bays Hill 41 60 Carpunghat Peninsula 44 70 Wingham 60 100 15 km upstream Wingham
Water samples were collected at each site at a depth of 0.5 metres and analysed at the Commission's Sydney laboratories for nutrients (ammonia [NH3-NJ, total Keldjahl nitrogen [TKN], nitrate/nitrite [NOx-N)), filtrable reactive phosphorus (FRP or OP), total phosphorus (TP), non-filtrable residue (NFR), volatile suspended solids (VSS), turbidity, conductivity, pH and chlorophyll a. The analytical methods used are detailed in Appendix B. In-field measurements included temperature, salinity/conductivity,' dissolved oxygen, Secchi depth, light penetration (at selected locations) and depth.' /!
N i ';:::'0/80'
;:;- /1 I;':. / 6> LJNot.ionol Po.~ (j ;' ( ( r--- , ,~
Mitchells Islond Ox ley Island e°'l• O~
.\\~ ~r,(,\
. ,vlv;. o 10 20 30 km ':Ju
Inlet • Sample Station • STW ® Industrial Discharp;e
Figure 2: Location of Sample Collection Sites 7
Table 3
Location of Stations on Manning River Tributaries ----. Distance Sta tion Tributary (km) Number Location ---- Dawson River 22 910 Pacific Highway bridge Dawson River 25 920 2km upstream Pacific Highway bridge Dawson River 29 930 North Coast rail bridge Dawson River 29 940 2km upstream ra il bridge Dawson River 30 950 Stony Creek confluence Cattai Creek 11 11 2km upstream Manning River Lansdowne River 12 12 1.5km downstream Manning River Browns Creek 26 45 Rail bridge Browns Creek 24 46 200m upstream Manning River
These measurements were taken at depths in the water column of 0.1, 0.5 and 1 m, then every metre to 6 m, then every 2 m to the bottom. Samples were also taken at depth where significant stratification was apparent from in field profile work. Specimens for algal determination were collected at sdccted site locations and examined for genus dominance.
The raw data collected from sample locations were stored on a Hewlett Packard 9836 computer using notations and a format available from the Clmmission; the complete data set excluding river profile data is also available from the Commission on microfiche. 8
3 CATCHMENT AND RIVER CHARACfERISTICS
3.1 Ca tchment Description
The M,lIlning River has a catchment ()f 8,400 km 2 rlsmg in the west at elevations of 1,280 m. Only, ,10 per cent of the catchment area could be considered re'asona,bly flat. T;,he river rises in the Mt Royal Range where· major tributaries .!lre the B,irnard, Nowendoc, Barrington and Gloucester Rivers, and Dorrigo,a'nd Cedar Party Creeks. In the lower catchment below Mt George, the vaHey broadens out forming a flood plain below Taree. II' was in this section of the river that most of the study was based. The major tributaries in the lower catchment include Browns and Cattai Creeks, and the Dawson and Lansdowne Rivers. The hydrology of the lower estuary is complex as the river forms a meandering network of narrow channels and passages. The river has a permanent entrance to the ocean at Harrington and an in t e rmi t ten t opening a t Old Bar via Farquhar Inle t.
Rainfall in the catchment is seasonal with the major falls between December and April with an average of 1,840 mm in the coastal region and 600 mm. in the upper catchment (Water Resources' Commission 1976).
3.2 Point Source Discharges
In the Manning Valley several industries and sewage treatment works are licensed under the Clean Waters Act, 1970 to discharge treated wastewaters t(l thc Manning River' and its tributaries. Table 4 presents information for each industry based on discharge requirements.
Table 4
Discharge Information ----. Maximum Discharge Maximum Limits Discharge Receiving Volume BODS NFR Type Location Water (kL/day) (mg/L) (mg/L)
STW Taree Browns Creek 4700 20 30 STW Wingham Manning River 970 20 30 Dairy Taree Manning River 350 600 1100 Dairy Taree Manning River 250 7100 1500
Discharge locations, are concentrated at two points along the river. These include the section adjacent to Taree where two dairies discharge to the main stream and a sewage treatment works discharges to Browns Creek, while uJlstream of these a sewage treatment works discharges to the main stream at Wingham. The volume of receiving water available for dilution at these loca tions is dependen t on the amount of freshwa ter inflow and tidal in f1uence. 9
3.3 Watcr Resources and River Flow
The int'erpretation of water quality data is based on' the consideration of land use activities and freshwater flow within the river during and prior to sampling. Water quality data have hcen grouped to represent five. river flow conditions, although only three of the conditions are to be used in later discussions as flood and drought did not occur during the study period.
Thc three categories of flow investigated are defined as:
High flow - no retention: freshwater plume present at river mouth, high surface run-off and flow contained within banks;
Medium flow - retention within lower flood plain area: saline influence in lower estuary, surface run-off; and
Low flow - long retention within full river (particularly the estuarine section): saline penetration well into the estuary forming a salinity gradient from the mouth to the tidal limit, minimal surface run-off with groundwater the main source of freshwater inflow.
Other flow conditions not investigated include drought where freshwater inflows are small and upper catchment flow ceases, and .floods where extreme surface flows result in river banks being breached.
Sali'nity, turbidity. and 'flow data (where available) were used in this study to determine flow categories for the Manning River and its tributaries. Salinity may be used as a measure of oceanic water penetration into the estuary and can help to indicate the potential dura.tion of pollutant retention in the river system. Figure 3 illustrates salinity data for the surveys at the river mouth (Station 10), and North Passage (Station 40) and Bay's Hill (Station 50), 23 and 38 km from the mouth respectively. Based on this information and other parameters, a ranking for flow categories was selected and is presented in Table 5. 32 ?\ I I \ \ ,~ I I \ \ ___ I , I \ ' 28 I \ -- HARRINGTON /" I \ I ' ! \ l'" (STATION 10) / " ,.... 24 +' II \\ I"I' I " " Q. II \\ II" ,,/" ' ' Q. ,I \ I ,/ ' '\oJ 20 , I \ I ',/ .... " \ II ,,\ I .....' :-.... " \ \ I j .. > ' ' \ \ \ II I ,"-"'-"-. r 16 ~. H , \ ! I' z / \ NORTH PASSAGE ' "-. H / '\ \ ! '" ...J 12 ' \ I ' • (STATION 40) I " a: (J) \ 'j \\// "-. /~. / a \ / ' \ I / V' "-.' \ ;' \ ~ j' BAYS HILL -./ e'"4 \ ' ~ (STATION 50) ,
... N ('I) 'lit" III to m m (Sl ... "" - - SURVEY NUMBER
Figurc 3: Sclected Salinity Valucs for Flow Charactcrisation 11
Table 5
Water Ouality Subdivisions Based on River Flflw ----- Survey Flowl Salinity at Flow Number Date (ML/day) Station 40 (ppO Category
1 11 Oct 84 1230 10 M 2 29 Nov84 2600 2 H 3 10 Jan 85 667 14 L 4 28 Feb 85 2870 0 H 5 18 Apr 85 768 14 L 62 21 Jun 85 2490 8 L 7 19 Sep 85 2339 12 M 8 14 Nov85 3470 7 M 9 13 Mar86 476 23 L 10 16 May86 611 21 L 11 26 Jun 86 452 16 L
1 The Killawarra recording station data were supplied by the Department of Water Resources. It should be noted that these are instantaneous and do not indicate rise or fall trends.
2 The survey was not complete and may not be fully representative of a low flow category as indicated by actu;,) flow data upstream. 12
4 WATER QUALITY IN THE LOWER MANNING VALLEY
The interpretation of water quality in the Manning River and its tributaries is hased on land use activities in the catchment as sampling 'locations can h" associated with a particular use which influences w;lter quality within a sub--catchment and flows within the river (Table 5). A ~ummarised version of the data based on median values is used in this discus:;ion to illustrate the r 4.1 Manning River The 'Manning River main stream was only investigated in its tidal section below Wingham, although limited samples were collected upstream at Station 100 (see Station description). Tempera ture and Dissolved Oxygen As Figure 4 illustrates average water temperatures varied between 18.5 and 2.'i°C while dissolved oxygen concentrations measured between 85 and llO per cent in surface waters. Both low and high flows showed lower concentrations cpmparcd with medium flows where maximum values of 110 per cent were recorded above Tarec (26 km). Salini ty Salinity was found in surface waters downstream of the tidal limit near Wingham (44 km) during low flows. The variation in salinity values during the three flow categories are presented in Figure 4. Clarity Clarity is a function of the suspended particles present in the water column and how much of the light which penetrates the water column is reflected, refracted or absorbed by these particles. Suspended solids also give an indication of silt and organic matter present in the water. Surface water clarity in the Manning was good for the full length of the river below Wingham (Figure 5) as Secchi depths averaged greater than 1.7 m during low flows. Clarity remained relatively good in the river above Taree and Bays Hill (38 km) during both medium and high flows with depths of over 1.7 m and over 1.1 m respectively. During medium flows the clarity improved with distance downstream of Taree. The impact of urban run-off from Greater Taree is a possible cause of the reduced clarity during medium flows in the section of the river nearby. Suspended solids or NFR (see Figure 5) were low for all flow conditions. Pcak concentrations of 9 mg/L during high flows, were measured in the river :",Ct-. ::- ..... c ... 1: ~ - !'1ED ruf'1 r-LOW ::: [ -'.~::':-:. ~~_c" I ~ a 3.0 . 7 ~J\'1 '" 2.5 E ..J, S m y/j -~~\ .... 2.0 , , E 5 ' ~----- J: -' ... I I ~------~ ,~----- ~r------_.v-"\, -' U ----:. ... --"" ---.., , .... _------... -- ...... ,\ / " . U Q: W L.. 1Il 1.5 , Z • 3 .----.-..¥-. """'-" . . ! 1.0 _._'-\ / 2 -- " .- \ , /' .5 - \' 0.0 B I ," 'C!) ., C!) ., C!) .., .C!) ., C!) II> m n m n m n m ~ m n N N '" '" .. .. N N ~ ~ ~ ~ 1S ! 10 i 1. ! 9 13 12 B 11 7 10 ...:J 9 ..J, 6 Z a m E 5 Dl 7 Q: U1 :J S U1 • ... 5 > • 3 3 2 2 ,~--~~::::::::::!.==.-~-=~=--:;:-~> ... '-",-, ", --'----'----'--",_-'-_--'-_-'----' o I ' -,.,....-,. 0C!)~I n m n m n m n m ~ m n m n m n m n m n t\I N ("l P'I .. .. t\I N ("l ("l • v DISTANCE (kml DISTANCE (kml Figure 5: Secchi, NFR, Turbidity and VSS: Manning River 15 section adjacent to Taree. During low·· flows, a peak concentration of 7.4 mg/L was found downstream of a major gravel extraction and crushing plant upstream of Tinonce (30 km). Turbidity was low « 5 NTU) during both low and medium flows but high values were measured between Tinonee and Croki (15 km) in high flows with peak values of 15 NTU adjacent to Taree. Nutrient.s Nutrient concentrations, as measured by total nitrogen (TN) and total phosphorus (TP), are an indication of the extent of eutrophication of a river and its potential to support nuisance algal or macrophyte growth. In the case of the Manning there was no evidence of major macrophyte or filamentous growth. Average nutrient concentrations for the main stream are summarised in Table 6 and presen ted in Figure 6. Table 6 Average Nut rient Concen t ra tions for the Manning River Flow Condition Low Medium High Station Distance TN TP TN TP TN TP Number (km) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 10 5 0.18 0.04 0.26 0.03 0.36 0.06 20 15 0.26 0.05 0.23 0.03 0.33 0.06 25 19 0.27 0.07 0.21 0.03 0.47 0.08 30 21 0.33 0.05 0.24 0.04 0.68 0.07 40 23 0.25 0.05 0.31 ·0.05 0.56 0.08 48 26 0.34 0.05 0.45 0.04 0.56 0.08 49 38 0.35 0.07 0.36 0.04 0.46 0.04 50 30 0.31 0.03 0.29 0.03 0.47 0.04 60 41 0.36 0.04 0.43 0.04 0.33 0.03 70 44 0.34 0.03 0.37 0.04 0.26 0.02 100 60 0.28 0.03 TN concentrations were low for the full length of the section of river studied during low and medium flows. High flows resulted in the highest concentrations, namely 0.68 mg/L in the South Passage (21 km). Total phosphorus concentra tions were low (0.03 to 0.04 mg/L) at the river mouth (5 kIll), downstream of Taree and upstream of Wingham (38 to 60 km) during low flows. However in the section of the river between Tinonee and Croki (adjacen t to Taree) eleva ted TP concen tra tions were measured (0.05 to 0.07 mg/L). During medium flows, low concentrations were observed except downstream of Taree where concentrations were 0.05 mg/L TP. High concentrations (0.06 .(0 0.08 mg/L) were found downstream of Taree during high flows. Under ·,ill flow conditions elevat"ed nutrient concentrations, particularly total phosphorus, were evident· either adjacent to or downstream of Taree. ,25 ~ . ,! LOW ~'-OW ,~J ~ ; : 3 ~ ,21 !'1EDIUI'1 FLOW 1.2 ,19 ! .... !GI...! C"'I....C"W I. I .,17 I." ...J ...J , .15 , 9' III III e .13 ,e .8 .7 a.. . II Z ~ ."9 ~ .6 .,5 ."7 .. , ...... ,Aoo.", .. ."5' ...... ------_...... '--.~~-:.:;.::::- ,,., .3 --__I -~- --, 01>-4-- .,"3 .2 --- ."1 .'I~ 151 ,'., 151 ., ':m ., 151 ., ,151 ., ., 151 ., 151 ., ..,151 WI 151 N N '" '" ... .. N N '.., .. '".. 15 .5 I. I" 13 13 12 12 II II ,~ I I I" .~-~ ...J, I" , I 0 , 9 0 1\ .... OJ ~ ::> II: 8 ....'~~ib! :---'..":::~",,,-,/1 -.;~ , e , '\': i /'\ ~ /I' .I ---_../ ,,:-; " I ...... '... \\\ 7 • \ I 7 I I...... \. a.. • ~I '" 6 "------= ~.. - \i,-/ ...J 6 / \ ~/ \ Z _---.--- \. ,J....Jt,...... J " . '~\ 5 >- ~- ',,' . I ~ ,, ,, a.. '' / ,, " V 0n: " I' ""--'"~\ \ 3 0 3 ~ ---J / . I _J II::::-----~ -V' .__ ~ 2 I 2 LJ ------It----~ ~--'---.,'---J---~I5Ic-~C---U1C---L-~I5I~--L---U1~--J---~I5Ic-~~~U1o---L-~~·--~ 151 U1 .. U1 151 ., 151 .., .., .. N N M ~ ~ ~ " ~ '" N '" '" .. .. " DISTANCE (kml DISTANCE (kml Figure 6: TP, TN, N:P Ratio and Chlorophyll .1: Manning River 17 Soluble nutrient concentrations (Figure 7) were variable with elevatcd NH3-N dllring low flows downstream of Bays Hill OX km, 0.04 to 0.0r. mg/U. C,)ncent rations were low during medium and high flows. N()x-N showed elevated concentrations during high flows particularly downstream of Tinonce to Dumaresq Island (19 km) where readings ranged from 0.07 to 0.65 mg/L. Concentrations were low for all other flow conditions. OP concentrations were generally low for all flows except in locations close to Taree and Wingham where distinguishable peaks were found.' Stimulation of algal growth by these nutrient concentrations was evident in the main stream during low flows downstream of Wingham to Taree with the peak average chlorophyll a concentrations measured at Carpunghat (41 km, 8.3 ug/U and Taree (11 ug/L). Highest concentrations of chlorophyll a were measured at Taree (12 ug/L) during high flows. 4.2 Dawson River The Dawson River, a major tributary of the Manning below Taree, was sampled because of earlier proposals to discharge treated sewage effluent to its waters from a newly constructed sewage treatment works. For comparative reasons, data from a mainstream station appears as the first point on each of the following figures summarising water quality. \ Salinity , the Dawson River during low and medium flows was influenced by saline waters from the main stream leading to a relatively uniform concentration up the river. Between 13 and 17 ppt (Figure 8) was measured for low flows and 11 ppt during medium flows. The concentrations were lower than the adjacent mainstream station. Dissolved Oxygen Dissolved oxygen saturation values were significantly lower than in the main stream. Saturation values declined· rapidly with distance from the Dawson's junction with the Manning (Figure 8) with values of 50 per cent saturation during low flows and 37 per cent during high flows measured in the upper reaches of the river. . Clarity Clarity was good (Figure 9) during both low and medium flows with Secchi depths of between 1.2 and 1.8 m. During high flows, Secchi depths of 0.5 m were mcasured. Turbidity during low and medium flows was low « 3 NTU) but elevated during high flows (18 NTU). Suspended solids. were generally low « 6 mg/L) along the full length of the river during all flow conditions with the exception of Station 920 (25 km) during low flows when a concentration of 12 mg/L was found. . Nutrients Total nntrient concentrations in the Dawson River as shown in Table 7 and Figure 10 were high (or TN in the upper section at Station 940 (29 km) and Station 950 00 km). s. 5. l: 0 J < ~ 0 0. 0 '"., ~ -' >: h L. :J :t: :J: .., _. W " " " T • 5£ r 5£ If .' I ~~ 0£ ) 0£ E ( cf. V 52 52 ~ w I,) u r. 1.", z 02 a: 02 ~ U1 ~ .. \ i U n. Cl ;. SI .. \t \ 51 IX '. bQ U \: I' \ al 01 \: 1\ \ \: OS :2 i 5 5 i:i u bQ ~----I....-~L....-I-.-J. 0 0 ...C III III III III III III ~ IV II) iD IV Q ...... II) .. • IV .. '" ...... Z (l/6W) N-xON ( l/6w) -~ dO OS :g.... u ~ "0 ~~-----,. ----.. -- \: S. 5. '" ..'" ------,=-:::.,-- \: .!:! 0' .... ,.---t-// z= 5£ : , SE U I I I :c I I = 0£ C 1-____ .. BE :I) I " E r:..: 52 52 " Col .~~I . ... W u = z bQ (f--~ a: / . 02 I- li: / 0Z / U1 .( , ~ , Cl , ,... 51 51 ,, \ ,, ~ V 01 01 ,' , / ,, \ ,, .J \ 5 5 0 oj. .. II) "- .. III I'l IV 01 "- .. I'l IV " :,'" IS> ...... • ...... (l/6w) (";/6w) N-EHN N)U :J: -. o --' :J: :J: "- 0 o--' x: ...--' ... ;! 3: 0 G ow~ J x: X ££ , , , , 1£ 62 E -'< w S2 u z a: I Ul £2 ~ Q 12 61 LI ~~---~-L~~~~--~~ __~-L __~~SI • N m m m • N m • S£ ££ 1£ y T'i ' \ ~ 62 62 I I (, f I ~ if ~a E -X f \ 1\ J w i \ n ~S2 uz -\ , , I I a: I / : Ul \ \ • I \ , £2 ~ {i Q \ ~ , \ I • 12 12 / I \\. \ \'. I/ I . \ i 1 61 \ \\ 61 LI In ., In ., on ., ... • '" N N (W) IH::l::l35 21 Table 7 Avcragc NUlrient Concentrations for thc Dawson River ------Flow Condit ion Low Medium High Station Distance 'TN TP TN TP TN TP Number (km) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 25' 19 0.28 0.07 0.28 0.03 0.47 0.08 910 22 0.44 0.05 0.23 0.04 0.89 0.10 920 25 0.39 0.05 0.68 0.08 0.92 0.08 930 27 0.42 0.03 0.54 0.05 1.20 0.08 940 29 0.75 0.06 0.38 0.04 1.10 0.07 950 30 1.00 0.03 0.81 0.06 0.90 0.05 ,- • This IS the firs t mainstream station downstream of the Dawson River. TN and TP concentrations were elevated during high flows for the full length of the river. TP concentrations were cleva ted at Station 940 (0.06 mg/L) ana also lower down the river ncar its junction with the main stream (0.05 mg/L) during low flows, while during medium flows concentrations ranged from 0.04 tCl 0.08 mg/L. Soluble nutrient concentrations (Figure 11) were generally low « 0.04 mg/L) for NH3-N during high flows but higher at some locations during medium and low flows (0.05 to 0.11 mg/L). NOx-N was low « 0.03 mg/L) except during high flows at Station 910 where there was an average concentration of 0.05 mg/L. OP concentrations were also low « 0.03 mg/L) except for Station 910 which was possibly influenced by the concentrations in the main stream or an adjacent caravan park. 4.3 Major Tributaries of the Manning River Water quality in tributaries of the Manning River wcre investigated including Cattai Creek (Station 11), the Lansdowne River (Station 12) and Browns Creek (Station 45). These tributaries recorded average water temperatures of between 22 and 260 C and were influenced by saline waters during low and medium flows (Figure 12). Dissolved oxygen saturation. was between 74 and 94 per cent in the Lansdowne River, 53 and 74 per cent in COl ttai Creek and very low - 11 to 33 per cent - in Browns Creek (Figure 12). Clarity Clarity was good during low flows in Cattai Cre,ek and Lansdowne River where Secchi depths (Figure 13) of 1.5 and 1.6 m respectively were recorded. Clarity was poor in Browns Creek where Secchi depths of only 0.8 m were measured. Clarity was reduced during higher flow conditions except in Browns Creek'where it' improvep 'from 0.3 m in medium, flows to 0.5 m.in high flows. , , .25 t LOH FLOW I.. l M£D !U!" COL ,...~; HIGH F"LOW I. 3 ~ .:: ~ 2 .19 1. r t I. I · 17 I . I! .J .15 -1 .9 , Cl , "E Cl .13 "E .8 I / ,I 11. ., >- .11 z >- .6 // II · I!9 .' , .5 / ; , • I!' / >-'" ~:.~. I ,, ... -, ..... _... ---..,( '---"... ______.... ~IL. ,A .. .I!' ... ~ --...... J' , 3 / .....- .. -._ .. '.-----"...;>' ..... ,.,.. ~, , '------.t.~'___" ...// .I!3 .. , . I, "'> • I! I t,' I'l. I'l .01 01 .'" .. .2,I." "" ~I " N N~ "."':::N N '" '" ~ '" N N '" '" '" 15 I I 15· I I. I I. I I 13 , I 13 'I 12 12 II -1 II II! , ' ,/ "Cl II! 0 .... 9 " \ >- . /...;... / a: 8 . " ... ,_/-' / -w""/ .. Q: , --.,f -1 n. > ...,/ -1 ; t 6 >- \ , I 6 z ~ 11. 5 " 0 5 ...... Q: ------"------~\.. " 0 ", ---.~. '-, • or' "" -1 • 3 I 3 U ---;/.,..--, ---\'\\'/ 2 2 ...... I! ~-"-~--L-~01C--"--L--~-"'~--'-·-""L--"--~"'~' --J m ~ ~ I! 01 PI ., " N N N N N ~ ~ ~ " '" N N "N '"N N I'l '" "I'l DISTANCE (km) DISTANCE (km) Figure 10: TP, TN, N:P Ratio and Chlorophyll a: Dawson River · I , .. I d; I · I I I 161 • I , I ,J'...... / / / "\ / 141 / ...... j .1 / , IV .J / .J , / , .121 ,/ m m / /\ E , I E / / / \ .101 / I Z of I I Z / I /~ I I , I X ,091 \ , I 0 / I ., I Z '"I 0.0 I I Z / / .061 0.0 ,041 0.0 )- , .02 I f / / '. B.e ' ,/ .001 :;:::;':'~::;':;::;:;'7~:';::;--~-;-:' , . on "- 01 In "- ai on "- 01 "- 01 on N '"N N N N '" '" '" "' N '"OJ "'N N N '" '" '" // 1.0 ,I .9 .105 X,- .9 ~ I I ,I r .095 I .7 / I ...J , ...J , I ! , I 1Jl ,/ OJ E .6 E .065 I / I / a.. Z .5 . / / 0 e- '" / .045 .4 "...,...... --~"t----r--~ ...... j / / "",'" " / , .3 ..... ------~ _. , ~~~--~' .025 t t..-- __ ---ft-...-- ...... ,/ -~ . ' .-~...<'- ~ .2 ' , -,' .:,--'---'-'" ...... _--, ...... L-__ L-~ __-L __ ~ ..L-~ __-L __ J- __","- __L-~.,c--L __~"-L--O. __~ ..L--" __ -L__ -L __ ~,,, __ -L_~ .005 .. N ~ 1O ~' ~!- -, . .1 ., on "- N N .. "' '" .. N N N N N ~ ~ M DISTRNCE (kml N '" DISTRNCE (kml Figure 11.: Soluble Nutrients and Keldjahl Nitrogen: Dawson River LOW fLOW MEDIU,-, FLOW HIGH FlOW ~ ~ ~ ~ {t::.MPERA fuRE oC 30 5AuNi iY (ppt) 30Ir------______~ 28 25 26 " 20 15 10 5 /// oi k"x)I'>s1' // / ~ IS1S1S?$l:-. " " I· .j I)XXX)f / ~ ( 1 11~ 12 £.! X DISSOLVED OXYGEN 8.5 pH 1~rl------~ 1 120 110 100 80 80 70 80 50! KXXXT ~ , , J." • "' rxxx>t%'f ,. . 1 II , STA.1l0N NUMBERS STATION NUMBERS Figure 12: Temperature, Salinity, Dissolved Oxygen and pH: Major Tributaries ...K1 .. ... '"z 0 "z .;:: 0 1= ~ .... '"=' '" ..,&J.. E-<...... 0 :; ::; -;;. "-.. ::E'" .§. .§. Vi ~ Il' v.: :I: Z ~'" ~ Jill ., > on 0 on 0 2 .. on .. .., 0 ::l Ii! N N ~ 2 '" '0= ~ '" !C ....>. '" .• S" W .•'0 " ,&J.. =' E-< ~ ~ p. ~ m :z. ....c ~ 0 ~ I'i...... K1 ..,. ..41 z :I "z 110 0 .. 1= ~ '" '"' i'? I e .~ u.. ...u ~ '" '"~ N N on on 0 on 0 " .., Ii! N N ~ 2 26 Suspended solids concentrations and turbidity were generally low « 5 mg/L or < 5 NTU) during low flows. These concentrations and values increased during higher flow conditions. Volatile or organic fractions were a significant component (50 to 65 per cent) of the suspended solids during all flows and at all locations. Nutrients Nutrient concentrations for both TP and TN were low for both Cattai Creek and thc Lansdownc River (Figure 14, Table 8) under all flow conditions. Nutrient concentrations were high in Browns Creek possibly as a rcsult of trcated sewage effluent discharged from Taree sewage treatment works. Table 8 Average Nutrient Concentrations for Manning River Tributaries Flow Condit ion Low Medium High St ation TN TP TN TP TN TP No. Tributary (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 11 Ca ttai Ck 0.39 0.02 0.17 0.04 0.91 0.04 12 Lansdowne R.O.25 0.03 0.27 0.03 0.545 0.04 no Dawson R. 0.44 0.05 0.23 0.04 0.89 0.10 45 Browns Ck 4.2 1.2 11 4.1 10 3.0 ---- High soluble nutrient concentrations were also found for all flows In Browns Creek (Figure 15). Nutrient concentrations in Browns Creek (Figure 14) stimulated algal growth as indicated by chlorophyll a concentrations. These ranged from 8.6 ug/L during low flows, 21 ug/L in medium flows and 3.4 ug/L for high flows. High ammonia concentrations and poor clarity would possibly limit the extent of algal growth in this creek and therefore the chlorophyll a measured is an underestimate of potential algal growth. The other two tributaries had chlorophyll a concentrations ranging from 3 to 7.4 ug/L. Nutrient ratios (Figure 14) were low in Browns Creek (3 NTU) possibly due to sewage discharge but higher in Cattai Creek at 15 NTU and the Lansdowne River with a reading of 10. 4.4 Quality of Effluent Discharged to Manning River The results of a survey of effluent quality from major discharges, summaris.ed in terms of concentrations and loadings per day, are shown 10 Table 9. The samples taken from these discharges represent grab and 24-hour composite samples. It was therefore evident that these discharges (dairies and sewage treatment works) have the potential to discharge high strength organic wastes with a high nutrient content in a limited section of the river near Taree if the location of the discharge is inappropriate or treatment processes are inadequate. en 0: CD"' ., III N "Z'" .. - Z .. 0 ., r= ... en~ ::I .;::,l:l E-< ~ .. -=- 0 0 ....., ...~ ::l!l.. ~ ?: ~ ~ iii I CD - ~ r ::! ~ .. 0 0 >. 0 0 l: L ~ ~ g N ~ ..c '" c.. ..0 0 ~ --=U "'"0 [] "' -=1::1 '" 01 .g...., : ~l ~ 1:1. :Z Z· E-< c: E-< lQ ~ "'CD .-i Z'" "Z III 0 .. r= ::I ~ !:II) en ii: "l 0 III ffi .;::IU ::I'" ::>z OS z ... 0 F = ~ :e.. "' E-o...... 0 OS ::E 'J "- '" i:i .S ~ IU z !. tIC • ~ 0 ;~ 0z II; ...... ,• 0 on "! on .., on "1 .., on N "1 'l 0 Z E 0 "! q .., -..c OS :~ .... ,-'3 :g > Q , ~ [3 m :I "0 I:l OS III '.~~ ... ,.- CI '< ..IU '1 m ..... Z= IU ::0 '0= 11.1 "' ,;.; .,"'" ... '"z "z IU 0 .. F ~ tIC= "' Ci: 'J "- !.'" z i ..,I :z: z ~ .., "; "; 0 '" on • "! "! "! "! 29 Table '9 Median Pollutant Concentrations and Approximate Loads of Discharges to t he Manning River Median Pollutant Concentrations Approx Loads (kg/day) BOD5 NFR TN TP Discharge pH Temp (mg/L) (mg/L) (mg/L) (mg/L) BOD5 NFR TN TP Taree STW 7.4 21.5 5 12 24 11 56 56 112 5 Wingham STW 7.4 24.0 14 12 23 7.5 14 12 22 7 Taree ])a iry(A) 8.7 720 240 61 8 250 84 14 2 Taree Dairy(B) 6.0 25.9 2300 770 55 6 580 190 14 2 30 5 FACTORS INFLUENCING WATER QUALITY IN THE MANNING RIVER Factors influencing water quality in the Manning River and its tributaries can be assessed in terms of the natural hydraulic constraints on river flow which leads to a partialIy mixed system, and the impact of point source discharges and polIutant loads from land use activities. 5.1 Hydrodynamic Factors The water quality data presented in Section 4 are based on samples collected within 0.5 III of the surface. The water column profile data collected from in-field measurements of salinity, temperature and dissolved oxygen concentrations showed that the Manning River was a partially mixed system downstream of Tinonee and upstream of Croki. This hydraulic feature was not observed in any other major North Coast river investigated during the Northern Rivers Water Quality Study. AlI other rivers, except for isolated decp holes, were well-mixed systems. For a partialIy mixed system like the Manning there is the potential for retention of contaminants where they are discharged at depth. This particularly applies near Taree. This is of concern as wastewater from two major dairies discharge to this bottom section of the water column. The partially mixed water body near Taree was also identified by the Public Works Department during a State-wide data collection program in 1981 and again in 1986 (see Public Works Department 1'185 and 1986). The Commission's study of the Manning system from 1984 to 1986 found water quality at depth to be poor in terms of dissolved oxygen saturation during some low and medium flows. The ext ent of dissolved oxygen depletion was a function of the time period since the previous significant rainfall event in the river catchment and subsequent volume of freshwater inflow. Figure 16 summarises the change.in dissolved oxygen concentration at depth during some low and medium flow periods. Concentrations were found to be significantly reduced at depth (2 m and below) compared with surface waters in the river between Croki and Tinonee. Figure 16 also presents error ba rs representing the wide range of ohserved saturations caused by the movement of tidal water which transports the lower water column up and down the r.iver. Therefore, the location of the poorest water quality at depth is dependent on the tidal stage at the time of sampling. Higher flows also resulted in low saturation values, although this was not unexpected as waters of this type are typically low in oxygen. Thus it was less easy to draw clear conclusions on this water quality parameter. The North Passage downstream of the Pacific Highway bridge was the major location where dissolved oxygen saturation values at depth were consistently low. Minimum saturation was measured at 42 per cent (Station 40) and represented a concentration of 3 mg/L (1100 hours). , The joint study conducted by the Commission and the Public Works Department in 1986 is detailed in the paper by Williams and Wyllie (1987). The study, using dye-tracing and current velocity techniques found that the surface (top 2 m) and the bottom Depth (m) - - - - - 0·5 3·0 -' -' :;; I « :z: V> « z (D ;,: 40 50 Figurc 16: Variation in Dissolved Oxygcn Saturation at Two Depths in the Manning River Velocity (ms-I) ~~l E 4UJ Dye Release· E· £ (8) 0. , ~ \ \ \ 4 1--_---11 E ;; ~ Cl 'l\Jl 15 17 Distance (km) Dye release [] Dye mo'Jemenl llJ12 24 It Salinity (%0) (---) 0---- Dye concentration (,ug L -I) 1m Final dye position Figure 17: Schematic Representation of Tidal Movement at Two Depths and Locations in I.he Manning River 33 . influcnn: in the main stream ncar thc Pacific Highway hridgc resulted in kngthy lag times between the change in direction of tidal velocity at the h 5.2 Point Source Discharges The impact of nutrients, organic or. suspended solids loads from licensed discharges can be identified at two locations on the Manning River. These included downstream of Wingham and a relatively long section of the river from Tinonee to Croki. The impact of point sources on water quality at these locations was principally evident at depth near Taree (Section 5.1) during low flows. Water quality adjacent to Taree (Figure 6) showed elevated nlltrient (TP and TN) conccntrations. An assimilation zone of 20 km was identifit:d in the main stream possibly as a result of nutrient input from Taree and Wingham. This zone was assodated with elevated algal growth (Figure 6 shows chlorophyll a concentrations between 5 and 11 ug/L) and declining OP concen tra tions (Figure 7). The organic loads associ a ted with wastes from dairies and in some instances sewage treatment works (Table 9) c(lnt~ibllted to the depressed dissolved oxygen concentrations in the river adjacent to Taree. However the localised influence of the discharges caused no significant deterioration in surface water quality. Browns Creek which receives treated effluent from the Taree sewage treatment works was severely affected (Section 4.3). Treated effluent from this works caused the creek's water column to be high in both soluble and total nutrients with poor clarity and low dissolved oxygen concentrations (zero during some surveys). The relative importance of other dischargcs 10 receiving water quality could not be established by this study. A gravcl extraction and processing plant upstream of Tinonee was found to increase suspended solids concentrations during low flows. Concentrations adjacent to the pllint peaked at 8 mg/L NFR (Figurc 5). 5.3 Urban Run-Off Thc Manning River was influenced by drainage from the urban arcas of Taree and Wingham during high flows. This was evident from increased average sllspended solids concentrations (8.5 mg/L and 7 mg/L respectively) nearby. Turbidity was also elevated during high flows with values of 12 NTU recorded ncar Tarce. 34 6 COMPARISON OF WATER QUALITY WITH OTHER NSW WATERWAYS The assessment of water quality in the Lower Manning Valley compared with olher NSW waterways is difficult and complex. The basic problem is that no two rivers have the same origin an!l hydrological characteristics nor are they affected by identical land uses. It is however valid to discuss the causes and response of rivers to pollutant loads that alter background water quality. For example, the causes of excessive nutrient concentrations may be similar but the actual con~entrations that stimulate nuisance plant growth may vary because of a nUtnber of factors. The impacts that result vary from system to system and have included dissolved oxygen depletion, loss of water clarity and excessive plant/algae growth. Threshold concentrations for TN and TP above whic):t nuisance algal or macrophyte growth could be expected were not reached. These concentrations are only approximate and cover a wide ra~ge of water bodies, so they vary slightly between loc'!-tions. T,,"e Au~trillian Environment Council and the Commission found a degree of uniformity between waterways and postulated threshold limits of 0.04 to 0.06 mg/L TP and 0.4 to 0.6 mg/L TN (AEC 1986) and 0.05 mg/L TP and 0.50 mg/L TN (SPCC 1985b). Concentrations in the M,!-nning River equalled or exceeded these concentrations for TP (0.05 to 0.07 mg/L) during low flows downstream of Tinonee. However TN conccp.trations were low and this was the possible factor limiting growth to below nuisance levels (although stimulation of plant growth was noted at some locations). Clarity was good in comparison with other water bodies (2 m Secchi depth) and was well in excess of desirable limits for Sydney' waterways (1.2 m, SPCC 1986). Dissolved oxygen concentrations ill surface waters were above 70 per cent saturation (desirab!e limit 70 per cent, 'SPCC 1986). However dissolved oxygen concentrations at depth were as low as 42 per cent (3 mg/L) adjacent to Taree. These concentrations were found in the water column below 2 m and represented up to 50 per cent of the water colump. in some locations. The concentrations in this zone of the river would have been low enough to cause fish death although there were sufficient good quality waters in the surface layer to sllPport fish. Table 10 compares major water quality characteristics of the Manning River with other waterways in the l'!orth (:oast area. A range of values is presented because of the wide variation in water quality throughout the systems. The Manning's surface water quality was similar to that of the Clarence River and could be classified as good if the section adjacent to Taree, discussed previously, is discounted. Clarity was good and suspended solids were low. 35 Table 10 Selected Water Quality Characteristics for Low Flows of North Coast Rivers TN TP Chlorophyll NFR River (mg/L) (mg/L) a (ug/L) (mg/L) Tweed 0.33-0.43 0.04-0.09 2 - 12 3 - 8 Brunswick 0.45-0.82 0.04-0.07 3 - 22 2 - 14 Richmond 0.30-1.30 0.06-0.21 2 - 20 2 - 14 Wilson 0.44-0.68 0.05-0.12 5 - 16 5 - 13 Clarence 0.28-0.50 0.03-0.07 2 - 7 6 - 16 Bdlinger 0.01-0.20 0.02-0.06 2 - 7 2 - 4 Kalang 0.04-0.11 0.02-0.05 2 - 4 2 - 5 Hastings 0.11-0.41 0.01-0.04 1 - 5 2 - 10 Manning 0.25-0.35 0.03-0.07 2 - 11 3 - 7 Notes: The values above derive from the relevant Northern Rivers Water Quality Study report. 36, i 7 CONCLUSIONS AND RECOMMENDATIONS Thc surface water quality in the Manning Rivcr was found to be good in tcrms or clarity and suspended solids loads during low flows. Phosphorus concentrations were elevated in the river section adjacent to Tarce and downstream of Wingham. Although this stimulated algal growth in an assimilation zone extending for 20 km between Wingham and Taree, it did not have a significant impact on beneficial uses of the stream. Water quality dL:terioration, although not severe in the abovementioned zone, could be a I tributed to treated effluent discharges from several dairies and a sewage treatment works near Taree. Water quality at depth (> 2 m) was poor as a result of hydraulic factors, and treated effluent and wastewater disposal strategies at the time of the investigation; however it should be noted that new strategies are being developed. Taree also contributed significant pollutants from urban run-off during high flows. This resulted in elevated suspended solids and a loss of clarity during Ihese flows. Gravel extraction and processing upstream of Taree was also found to be influencing suspended solids concent ra tions during low flows. Browns Creek was impacted by treated effluent from Taree sewage treatment works 10 such an extent that it could only support limited aquatic life. Odours were also associated with this creek. The Dawson River had poor quality due to natural causes indicating that the river is not capable of receiving effluent containing oxygen-demanding wastes or nutrient concentrations that would increase the receiving waters to above threshold levels (Section 6). Cattai Creek and Lansdowne River were found on occasions to have poor clarity during low flows, cause unknown. On the basis of the water quality study carried out in the Manning catchment the following RECOMMENDATIONS below are made. The current review of dairy wastewater disposal strategies should be require the compa~ies to either discharge to sewer or pre-treat effluent to 20 mg/L BODS and 30 mg/L NFR and discharge it to surface river waters if Ihe discharge is still to continue. The current augmentation of sewage treatment works in the Taree area and the new disposal strategy at Goat Island should be monitored by the Greater Taree City Council for impact on receiving water quality discharge and this should form part of the licence condition. Changes to discharge depth may be required if water quality (as monitored by the council) is adversely affected by this discharge. Discharge of treated sewage effluent is not recommended for the Dawson River due to its na turally poor condition during low flows. This would include oxygen demanding and nutrient wastes. The council should be advised of the impact of urban run-off on the river during medium to high flows and requested to review current urban drainage facilities and adopt controls where practicable, particularly in new development areas. The Commission should review the gravel extraction industries with the view of advising on housekeeping or processes and practices to reduce suspended solids loads entering the river during low flows. ·37 The Commission should draw this report to the attention of other relevant authorities and inter-departmental commit tees and should carry out a follow-up study in five years. 38 8 REFERENCES Australian Environment Council (1986), Nutrients in Australian Waters, Canherra. Public Works Department (1985), Manning River Tidal Data 14th October 1981 and .I1lh November 1981, Report No. 380, Sydney. Public Works Department (1986), Manning River Tidal Data 11th March 1986, Report No. 958, Sydney. State Pollution Control Commission (1985il), Water Quality In the Tweed Terranora Estuary, Sydney. SI ate Pollution Control Commission (1985b), Strategy for the Management of the Water Quality of the Hawkesbury and Nepean Rivers, Sydney. Slate Pollution Control Commission (1986), Pollution Control in Sydney's W,1terw.1Ys, Sydney. Water Resources Commission (976), Water Resolirces Inventory, Sydney. Williams, R.E. (986), Development of Disposal Strategies in the Tweed Tcrr,1nor,1 Estuilry, Hydrology Symposium, Institute of Engineers, Brisbane. Williams, R.E. and Wyllie, S. (1987), The Retention of Pollutants and the Rel,1ted Tidal Characteristics of the Manning River, 12th Federal Convention Australian Water and Wastewater Association, Adelaide. ,0 39 Appendix A Station Locations Waler Quality Stations (* discharge si te; @ road station) Slation Km No. Upstream Reference Comments ---- 005 4.7 CUN588656 Manning River bridge at "Merlin" south channel 010 3.9 CUN672718 DIs end Pelican Point, Manning River 011 10.0 COO658765 Cattai Creek, on ·bend 300m uls small island (tribu tary input) 012 11.5 COO631768 Lansdowne River 1km above Tappin Creek, "T" junction of ove rhead wires 020 15.2 CUN583718 Manning River 2km dIs Dumaresq Island, at start of trees on starboard bank 910@ 22.5 CUN530710 Dawson River, Pacific Highway bridge 920 25.2 TAR513715 Dawson River, overhead wires 2km uls Pacific Highway bridge 930 27.0 TAR507729 Dawson River at North Coast rail bridge 940 28.2 WIN492737 Dawson River, 2km uls rail bridge, overhead wires 950 29.2 WIN488751 Dawson River-Stony Creek confluence, 3km uls STW 025 19.5 CUN558693 Manning River, 2km dIs Dumaresq Island bridge, house with banana trees starboard side 030 22.0 CUN533683 Manning River, South Passage, overhead wires, 3km dIs main river channel (Middle South Passage) 040 23.1 TAR526705 Manning River, sou th side of Goa t Island, North Passage, u/s Dawson, dIs .' Taree 041.1* 24.8 TAR510699 Manning River. Co-op discharge, drain adjacent to amenities building, to river bed 041.2' 24.8 TAR510699 Manning River Co-op discharge, main drain, sample at pit' outlet 40 ------_._-- Watcr Qualiiy Stations (. = discharge site; @ road station) St a tion Km No. Upstream Reference Coinments 041.3* 24.8 tAR510699 U/s discharge In bushes 042* 25.1 TAR505695 Peters Creamery, drain Him dIs of Peters wharf 044* 27.5 tAR49i699 STW discharge to Browris Creek, 0.5km uls of Station 45 045 26.9 t AR498695 Browns Creek rail bridge 046 25.4 t AR502695 Browns Creek, cippi)site boa t hire 048 27.2 'rAR489685 Manning River, O.2km dIs Pacific Highway, bridge opposite Taree 049 30.8 TAR461662 Maiining River, 3km u/s Taree 050 37.8 TAR456703 Power lines; 3kin uls Bays Hill Lookout 060 4L7 tAR432727 Manning River; Carpunghat Peninsula 44.2 WiN422'137 snv Wingham, small trickle filter, dIs of boa tramp 070 45.0 T AR4117:h Mail~irig Rivet, 600m dIs' Wingham bridge 41 Appendix 8 Analytical Muthods Tne Commission laboratory at Lidcombe is modern, automated and maintained to carry out routine chemical analyses on water and wastewaters. The analytical assays as carried out in the Northern Rivers Water Quality Study were: ------Type of Analysis Instrumentation and Techniques Used pH Metrohm Hcrisav pH meter ES12 at 250C Conduct ivity Extech digital water analyser at 250C Turbidity Hach model 2100A turbidimeter; based on degree of light sca ttering Non-filtrable residue 'Standard Methods", 15th edition, 1980, pp. 94-6 Vola tile suspended solids 'Standard Methods', 15th edition, 1980, pp. 94-6 Nutrien ts: Analysed on Technicon autoanalyser A.A.(R) II NHrN by colorimetry (method of Jirka et al. 1976) NOx-N FRP TKN TP Chlorophyll a Commission method using Turner fluorometer modellO series and SCOR-UNESCO method 1966 BOD5 "Standard Methods", 15th edition, 1980 ------ ~'PIIIN1f[) ~"'.u.STR"'IA DWUI ~J ..' ... n" .. I.