2 Renmark to border LAP area assessment - EPA - Sa.gov.au

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River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options Table 7.2 lists the aquatic ecosystem risks identified in the GW & CD LAP areas which are discussed in more detail below for each stressor. Nutrients It is generally true that excessive levels of nutrients pose a risk to aquatic ecosystems because of the tendency to encourage dominance of algal species that are less desirable (and less representative of the natural conditions), and to promote excessive weed and algal growth. Algal blooms in the Lower Lakes are also closely linked to environmental conditions (eg turbidity, temperature, water residence times) as well as nutrient inputs (eg Geddes 1988). Several (6) high nutrient risks were identified, mostly event discharges from the Angas, Bremer and Finniss rivers, and Currency and Tookayerta creeks into Lake Alexandrina. Many of these creeks/rivers have low flows during summer/dry conditions but rainfall events are likely to send a significant pulse of nutrients down the catchments to the lake (see EPA 1998a for a summary of water quality data and the DWLBC surface water archive for river flow data). The catchments for several of these are in the Mount Lofty ranges and experience higher rainfall rates (higher likelihood values) than other creeks entering the River Murray. At this stage of the study the outlets of the creeks/rivers to the lakes were assessed as individual hazards (sum of all catchment hazards). Land-use in these catchments is mixed but includes large areas of irrigated horticulture (eg 7869 ha in Angas-Bremer in 2005) including large vineyard areas (eg on Finniss, Currency, Bremer), townships (Mount Barker, Bremer catchment; Strathalbyn, Angas catchment), dairy farms (eg on Tookayerta), and mines (eg on Dawsley Creek, Bremer). Stage III of the project will examine catchment risks in more detail. Salt Creek discharge was assessed as a moderate nutrient risk although there was a large degree of uncertainty as to its overall impact, if any, on the Coorong water quality. DWLBC is currently undertaking detailed monitoring and risk assessment work on Salt Creek. Horticultural areas immediately adjacent to the lakes and Coorong received a moderate risk ranking (although the certainty value for this was noted as low, indicating the need for further research). Horticultural land uses dominate the river and creek catchments. Both LAP groups have identified sustainable agriculture as being a priority in the region. Land use must be matched to land capability and water usage and application rate is also needed in this area to reduce drainage volumes. The GW LAP irrigation management program aims to support community initiatives for managing irrigation to achieve efficient water use within the area. The program includes targeted irrigator training and awareness raising, and land and water management planning for sustainable use of land and water resources14 . Other agencies such as DWLBC, EPA and the SAMDB NRMB (formerly catchment) boards are actively involved in catchment-scale land management issues in this region, and monitor ground and surface water quality and quantity. Stormwater discharges from the urban catchments in Goolwa, Meningie and Clayton were categorised as a moderate risk. Most nutrients from stormwater are likely to be in organic form (plant and detrital material) and not immediately bio-available (not likely to cause wide-scale algal blooms). A higher cumulative risk may exist in the Goolwa area where several (15) outlets enter into a reasonably narrow 14 See GW LAP website for more details, 198
River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options channel with flow restricted by the Goolwa barrage. Some of these discharges are directed into reed systems when they enter the lake, others have gross pollutant traps (GPTs), and some discharge directly into the lake with no prior treatment. At Clayton, nine discharges were assessed, with stormwater filtering through grass swales before entering the lake. At Meningie, seven discharges were assessed. A significant amount of Meningie’s stormwater is diverted through a GPT and into the Falkner Street retention basin. At the community workshop locals commented that this basin periodically overflows and discharges directly into Lake Albert. The majority of Milang stormwater is also discharged, through a GPT and filtered by a grass bank, into a wetland. Management strategies have also been developed to help address stormwater risks (Alexandrina Council 2003; Coorong District Council 2004). Several marinas15 and vessel mooring areas in the Goolwa-Hindmarsh Island area were categorised as a moderate risk. Many of the marinas have no pump out facilities and are not licensed by the EPA. The exception to this, The Marina, Hindmarsh Island, is part of the global ‘Clean Marinas‘ program, has an accredited EPA licence and has very good environmental management systems. It was given a low risk rating on this basis. Some live-aboard accommodation (eg paddle steamers Goolwa and Federal) was given a moderate risk as it was unclear how their waste is disposed of (the vessels do not move according to community informants). Accidental vessel blackwater spillage at the Goolwa river vessel waste disposal station was classed as a moderate risk. The station is quite exposed making operations during windy conditions difficult. Toilets/septic tank systems in several locations received a moderate risk ranking. Septic tanks pose most risk when they have a high density of soakage trenches in a particular area, for example on the north side of Hindmarsh Island the high density is of particular concern given the flow restrictions in this area (imposed by the Goolwa barrage). Several other shack (eg Murray Mouth, Mundoo channel), accommodation/caravan parks (eg Hindmarsh Island and Goolwa caravan parks), and a township (Clayton) received moderate risk rankings. Goolwa, Milang and Meningie townships have STEDS. The Milang south shores shacks are being connected to STEDS but this was not fully operational so a moderate risk was also assigned. Goolwa STEDS was overflowing and leaking to groundwater at the time of inspection but this received a low risk ranking due to its distance from the lake. The Alexandrina Council (with funding support from SAMDB NRMB) will shortly upgrade the lagoon system to a treatment plant with storage and reuse of effluent for the irrigation of lucerne on recently acquired council land. Dairy farms also produced a moderate risk rating, predominantly through leakage to groundwater. There are a number of farms in the Coorong and Lower Lakes area where the groundwater table is quite close to the surface and nutrients (in particular nitrate) can readily enter the groundwater and subsequently reach the Coorong or Lower Lakes. The high number of farms may also present a cumulative risk in some locations (eg south-western area of Lake Albert). Unrestricted access by beef and/or dairy cattle to the lakes for drinking water and grazing riparian vegetation, posed a nutrient risk in several locations. These were assessed as low-moderate risks depending on an assessment of grazing pressure and location. Low risk sources included informal camping areas, some grazing locations, livestock grazing, wetlands and wastewater infrastructure failure. 15 A marina is defined as a formalised mooring location (more than five boats), often with additional facilities (eg slipway, wastewater pumpout, refueling station, office). 199
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The River Murray and Lower Lakes ca
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6 Mannum to Wellington LAP area ass
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Table 6.5 Frequency of risk to recr
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Figure 7.2 Example of hazard to wat
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Roz Becker, Riverland Tourism Assoc
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Abbreviations 10 ADWG Australian Dr
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Executive Summary The River Murray
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River Murray and Lower Lakes catchm
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