River Murray and Lower Lakes Catchment Risk Assessment for Water Quality: Results and Management Options

River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options 5 Mid Murray LAP area assessment 5.1 Description of the area The Mid Murray Local Action Planning (MM LAP) area extends along from Lock 1 at Blanchetown to Mannum (Figure 5.1). The area is characterised by limestone cliffs and floodplain wetlands and includes the townships of Blanchetown, Swan Reach, Nildottie and Purnong. The area has a small permanent resident population (approximately 4000 people) but this can increase significantly during holiday periods, as up to 80% of all river shacks are located within this area (MM LAP 2000). Popular shack areas such as Walker Flat and Bowhill are also associated with significant recreational river craft activity. The MM LAP area encompasses approximately 1600 ha of irrigated horticultural areas (mostly vegetables, vines, citrus and stone fruit). Other land uses within the area include sheep and cattle grazing, and cropping. The MM LAP committee has identified a number of key issues in the area that are of concern, including natural habitat degradation, unsustainable agriculture, unsustainable recreational use and declining water quality (MM LAP 2000). Current8 key implementation activities are focused around: • revegetation and biodiversity plans • improvement of wetland habitat through surveys, management plans and on-ground works • education and awareness including irrigation efficiency training workshops. Within the MM LAP area, water quality monitoring sites are located at the raw water off-takes for the Swan Reach town supply and the Mannum–Adelaide pipeline respectively. Monitoring is carried out regularly on a wide range of parameters. Water quality within the region is fair compared to the rest of the river. Nutrient levels are generally steady, with slight increases in soluble nitrogen, phosphorus and E coli levels towards Mannum. Total heavy metals at the monitoring stations in this area were generally at a low level and pesticides were generally at or below detection levels. Turbidity levels in the river are high from where the river enters South Australia to the mouth, significantly influenced by contributions from the Darling River (which has a high clay colloid level) and flood events (MDBC 1988). ‘Run of the river’ data collected by DWLBC indicates that saline groundwater inputs entering the river in this area are lower than in the Riverland. The MM LAP committee commissioned an in-stream salinity survey of the river from Wellington to Blanchetown in 2005, which will provide additional information about salt accessions to the river. 8 See <www.rivermurray.sa.gov.au/lapgroups/mid/index.html> 118 River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options Figure 5.1 Map of the Mid Murray LAP area 119 River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options 5.2 Environmental value zones Spatial zones assigned for each environmental value allowed hazards to be identified and assessed for risk in manageable amounts. Aquatic ecosystem zones Risks to aquatic ecosystem health were assessed in arbitrary three kilometre zones for the length of the river, a total of 41 zones in the MM LAP area. Raw water supply zones Two raw water supply zones (from 500 m downstream to three kilometres upstream of each potable water off-take) were identified in the MM LAP area: MMRAW001 Swan Reach Water Treatment Plant (Swan Reach to Stockwell pipeline) MMRAW002 Swan Reach township (unfiltered). Recreation zones Eight recreation zones were identified in this LAP area: MMREC001 Blanchetown and surrounds (3.6 km long) MMREC002 Swan Reach to Big Bend (13.1 km long) MMREC003 Nildottie and surrounds (10.2 km long) MMREC004 Walker Flat and surrounds (10.9 km long) MMREC005 Caurnamont to Purnong Ferry (4.2 km long) MMREC006 Bowhill Wharf to Piggy Flat Landing (5.0 km long) MMREC007 Teal Flat South to Truman’s Boat Ramp (8.0 km long) MMREC008 Younghusband to Kia Marina (9.2 km long). 5.3 Hazard Identification process A community consultation workshop was held with representatives from the Mid Murray LAP group; Loxton/Waikerie and Mid Murray councils; Boating Industry Association of South Australia; Mannum Marine; and landholders from Swan Reach, Nildottie and Purnong. The workshop identified the nature and location of potential water quality hazards and recreation zones, and provided useful information for the subsequent risk evaluation process. 5.4 Risks to water quality in the Mid Murray area A total of 188 hazards were identified in the Mid Murray LAP area. The highest frequency hazards were toilets/septic tanks, boat ramps, wastewater/STEDS infrastructure, systems, informal camping areas (no sanitation facilities), vessel/ houseboat moorings, and wetlands/lagoons (Figure 5.2). Frequency (occurrence) does not necessarily indicate risk—a hazard may have a high frequency but a low risk. The cumulative impacts of low-risk activities will be considered and assessed as part of mitigation strategy development. 120 The attachedDVDhasindividual mapsnumberedaccordingtothekeymap. Figure 5.4isthekeymap for riskstotheaquaticecosystemenvironmentalvalue intheMMLAParea. Risks toaquaticecosystem health River MurrayandLowerLakescatchmentriskassessmentforwaterquality:Resultsmanagementoptions Number of hazards Figure 5.2 LAParea MidMurray Frequency ofhazardstowaterquality, 10 15 20 25 30 35 40 0 5 Figure 5.3 Example ofhazardintheMMLAParea:dieselpump Chemical Store Landfill Petrol Station and fuelstoreneartheriver Refuelling Facilities Vessel Waste Disposal Station Creek/River Ferry Horticulture Slipway Marina Stormwater Infrastructure Grazing Fuel Store Wetland/Lagoon Vessel Mooring(S) Informal Camping Wastewater Infrastructure Vessel Launching/Boat Ramp Toilets/Septic Tanks 121 River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options Note: shaded maps only are included on the attached DVD; not all maps have hazards associated with them Figure 5.4 Key map for aquatic ecosystem zones 122 River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options Table 5.1 summarises the frequencies of identified risks for the various water quality stressors. The highest frequency of risks was for nutrients and organic matter, followed by turbidity, hydrocarbons, salinity, heavy metals and pesticides. The majority of these risks (304) were rated as low level but a significant number of moderate (242) and a few (3) high-level risks were recorded. Table 5.1 Frequency of risks to aquatic ecosystem health, MM LAP area Stressor Risk NU TU OR HM PE HY SA Total Low 52 87 56 12 15 81 1 304 Mod 99 8 95 7 1 1 31 242 High 1 1 1 0 0 0 0 3 V high 0 0 0 0 0 0 0 0 Total 152 96 152 19 16 82 32 549 NU—nutrients; TU—turbidity; OR—organic matter; HM—heavy metals; PE—pesticides; HY—hydrocarbons; SA—salinity Table 5.2 lists the aquatic ecosystem risks identified in this LAP area, which are discussed in more detail below for each stressor. Nutrients The Marne River was identified as the sole high nutrient risk. This river has low flows during summer/dry conditions but large (relatively infrequent) rainfall events send a significant pulse of nutrients, sediment and other contaminants down the catchment (see EPA 1998a for a summary of water quality data and DWLBC surface water archive for river flow data). Risk assessment of the entire Marne River catchment was considered outside the scope of this phase of the study so the outlet to the river were assessed as an individual hazard (sum of all catchment hazards). Land-use in the Marne catchment is mixed but includes large areas of irrigated agriculture (mainly lucerne, vegetables, pasture, vines), piggeries and poultry farms. The large number of toilet/septic tank risks in the MM LAP area (eg Teal Flat, Jyllunka, Younghusband Holdings shacks; Purnong, Swan Reach townships; Blanchetown Riverside and Grulunga caravan parks, commercial houseboat near Greening’s landing) were mostly classed as a moderate risk. The potential risk from septic tank systems arises through overflow of tanks and leakage of effluent from soakage systems to groundwater and the river. High-seasonal use sites may boost the likelihood of overloading and failure of systems. A number of sites within this LAP area are already on STEDS (eg Big Bend, Marks Landing, Bowhill and Greenway Landing shack sites) and schemes for Jyllunka and Younghusband Holdings shacks are in progress. It is understood a number of other areas have been identified for capital works to upgrade from septic systems to STEDS. The Mid Murray Council levies individual shack owners (typically $4000-7000) to pay for these schemes. The risk from infrastructure failure of STEDS pumps/pipes was assessed as low for several locations. Discharges from vessel mooring sites (eg Schuetze, Hermann and Preiss landings) and marinas (eg Kia, Temptation houseboats, moorings north of Mannum, Mannum Marine) were identified as a moderate risk. 123 River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options Greywater and blackwater discharges contain high levels of nutrients and some permanently moored houseboats are of particular concern. The river vessel waste disposal station at Swan Reach was identified as a moderate nutrient risk. The current Swan Reach station has experienced problems with leaching of the soakage trench, and an upgrade of this system to STEDS is planned for the very near future. The lack of a vessel pump-out station between Swan Reach and Mannum (96 km) has long been identified as an issue; the area supports moderate to high frequency boating use (BIASA 2001). Recently, a working group formed for installing a new station at Walker Flat, which would reduce the risk of illegal blackwater discharge in this area. Discharge and event discharge from wetlands and lagoons was assessed as a moderate nutrient risk (eg Swan Reach complex, Kia and Devon Downs North wetlands, Lake Carlet, Maidment, Purnong and Caurnamont). There is some uncertainty to this ranking due to limited monitoring data on nutrients.

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