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

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.
Given that wetlands are a natural and intrinsically important part of the river ecosystem, they are not a
‘risk’ in the conventional sense. Therefore, management should be focused on reducing inputs of
contaminants from wetland catchments and ensuring that artificial flushing management strategies are
properly undertaken to minimise any effects on river water quality. Recent basic monitoring at a number
of wetlands in this area, as part of the River Murray Wetlands Baseline Survey, included Devon Downs
south, Kroehn’s Landing, Foster’s Lagoon and North Purnong, Lake Carlet, Younghusband and Sweeney’s
Lagoon (Moorundi complex). The survey collected data on site physical characteristics, water quality,
groundwater inputs, vegetation, fish, birds, frogs and macro-invertebrates. The Mid Murray LAP group
also coordinated wetland baseline surveys for Morgan’s Lagoon (Moorundi complex) and Sugar Shack
Lagoon (Swan Reach complex) and will be coordinating further baseline surveys at Devon Downs north,
Noonawirra Lagoon (Moorundi complex) and Saltbush Flat in 2006. The data will be used to identify
conservation values and management objectives for each wetland (eg salinity, dissolved oxygen,
turbidity).
Several stormwater discharges were classed as a moderate risk (eg Swan reach). The general lack of
comprehensive stormwater infrastructure in smaller townships and shacks areas in the Mid Murray LAP
area means stormwater eventually reaches the river as diffuse flow. Some ‘natural’ filtration of the
water takes place as it passes through vegetation and wetland areas. Long Gully Road (just north of
Mannum) stormwater discharge was noted to have problems with drain blockage and this area has
flooded in the past. Mid Murray Council is currently addressing this issue.
Grazing of the riparian margin was identified as a moderate nutrient risk in several areas (eg north of
Younghusband west wetland, Cowirra landing, upstream of Swan Reach, Blanchetown).
Horticultural areas (Swan Reach area, Greenways, Mondello’s) were identified as a moderate nutrient
risk. Irrigated horticulture is the primary agricultural production activity in the MM LAP area with over
1600 ha of crops (vegetables, stone fruit, citrus, vines, lawn) located mainly on the highland areas (MM
LAP 2000). There have been changes to more efficient water delivery systems and the LAP group, as part
of the ‘improving irrigation efficiency project’, has run irrigation management workshops. The water
allocation plan for the river has increased the awareness of all irrigators of the need to meet an 85%
water use efficiency benchmark each season under the plan. Further education and awareness will
continue to improve efficiency, decrease water use and minimise drainage. Other examples of MM LAP
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