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 2 Renmark to border LAP area assessment 2.1 Description of the area The Renmark to border Local Area Planning (RB LAP) area, of approximately 170,500 hectares, is located in the South Australian Riverland (Figure 2.1), in the District Council of Renmark Paringa. Major towns are Renmark, Paringa and Lyrup. The LAP area encompasses a significant expanse of backwaters to the river proper, most of which are accessible for recreational use (eg canoeing, boating). 20 Figure 2.1 Map of Renmark to border LAP area
River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options Land and groundwater salinisation is a major problem in the area, largely the legacy of historical vegetation clearance in the regional catchment. The salinisation problem has been exacerbated in some locations by irrigation creating a ‘groundwater mound’ and increasing saline groundwater flows to the floodplain and river. Large areas of the Renmark region, currently used for viticulture and citrus horticulture, employ drip and/or under-canopy irrigation practices that are generally much more water efficient than historical flood irrigation methods3 . Much of the irrigation drainage is now collected in caissons and pumped to regional disposal basins (eg Noora; DWLBC 2003b), where evaporation delays seepage back into the groundwater or the river. The Renmark Irrigation Trust controls most inland water licences in this area; the Central Irrigation Trust (CIT) also operates in the Chaffey Irrigation Area. Generally, water quality within the RB LAP area is fair compared to the lower reaches of the river (EPA 2001a). Monitoring is carried out regularly on a wide range of parameters across the border in Victoria (at Rufus River) and just downstream of Renmark (at Lock 5). SA Water also monitors some water quality parameters at the Renmark Water Treatment Plant (WTP) off-take. The ‘run of the river’ and other salinity surveys (by DWLBC) have identified areas of the river receiving large salt inputs from groundwater (eg Chowilla area). It is also anticipated that a large quantity of salt currently trapped in floodplain sediment will enter the river if the area floods in the future (CSIRO 2003). In terms of this project’s framework, saline groundwater inputs were quite difficult to define for a precise hazard location, as they diffuse into the river to varying degrees along its whole length. Specific salinity risks that could be attributed to defined source locations (eg large horticultural areas, saline creek/drainage discharges) are included in this report. Dissolved nutrient (oxidised nitrogen and phosphate) and E coli levels were on average much lower in the RB reach of the river than the Lower Murray (EPA 2001a). Total heavy metal levels at monitoring stations in this LAP area were generally at a low level, with pesticides generally at, or below, detection levels. Turbidity levels in the river are elevated from where the river enters South Australia to its mouth (EPA 2001a). This is significantly influenced by contributions from the Darling River (which has a high clay colloid level) and flood events (MDBC 1988). 2.2 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 38 zones in the RB LAP area. Raw water supply zones Three raw water supply zones (from 500 m downstream to three kilometres upstream of each potable water off-take) were identified in the RB LAP area: 3 While water use efficiency based around low rate water application systems is growing, an apparent accumulation of salt in the root zone of the irrigated crop is increasing. 21
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