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 The frequencies of identified risks to raw water supplies for the various water quality parameters are summarised in Table 6.3. The highest frequencies of risks were for the parameters of nutrients and pathogens, followed by organic matter and hydrocarbons. The majority (67) of these risks were rated as low, but several moderate (74) or high (17), and one very high risk was recorded. Table 6.3 Frequency of risks to raw water supplies, MW LAP area PA—pathogens; NU—nutrients; TU—turbidity; OR—organic matter; HM—heavy metals; PE—pesticides; HY—hydrocarbons; SA—salinity Raw water supply risks identified in this LAP area are listed in Table 6.4 and discussed in more detail below for each stressor. Pathogens A high pathogen risk was assigned to several discharges from the flood irrigated dairy farm areas (Pompoota, Cowirra, Mypolonga, Wall Flat). The relatively close proximity of these discharge points to their respective unfiltered small township water supply off-takes, creates a high risk from pathogens (eg Cryptosporidium sp10 and Giardia). SA Water is currently addressing these risks by: • increasing separation distances between discharges and off-takes with channel modifications (eg Pompoota) • undertaking capital works such as a proposed new pipeline under the river to connect Jervois township to the Tailem Bend supply • examining the feasibility of treatment plants for the small township supplies • installing timers on discharge and off-take pumps to prevent simultaneous operation (eg Wall Flat). Discharges from Toora irrigation area were considered to have a moderate risk level as only one dairy farm remains operational. It potentially impacts the large Murray Bridge–Onkaparinga off-take but this water is filtered so a lower risk would eventuate (once water enters treatment plant) than for the small unfiltered township supplies. The significant rehabilitation project underway in all areas of the LMRIA will significantly reduce the general level of raw water supply risks. Mannum stormwater discharges and vessel/houseboat discharges present a moderate risk ranking for pathogens due to their close proximity to the off-take. The discharge at Berryman Avenue, which is very close to the Mannum off-take, is particularly concerning and received a high risk ranking. 170 Stressor Risk PA NU TU OR HM PE HY SA Total Low 37 45 16 37 14 18 34 25 226 Moderate 14 14 11 19 6 0 9 1 74 High 10 2 2 4 0 0 0 0 17 Very high 0 0 0 0 0 0 0 0 1 Total 61 61 29 60 20 18 43 26 318 10 Calves in particular are known to contain high levels of Cryptosporidium sp
River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options Informal camping areas at Mypolonga and Wall Flat were given a moderate risk ranking due to their proximity to the respective township water supply off-takes, absence of sanitation facilities and high occupancy by campers during holiday periods. Low level risks included Tailem Bend stormwater discharges, ferry deck runoff, houseboat discharges (other than those in Mannum mentioned above), wetlands and septic tank effluent discharges (eg Sunnyside and Avoca Dell). The septic tank discharges had a high likelihood but relatively low consequence but this ranking had some uncertainty associated with it. In general, a low risk ranking to raw water supply environmental values reflected a lower likelihood of stressors from a particular hazard reaching an off-take. For example, all stormwater discharge points at Tailem Bend are more than one kilometre upstream of the off-take and significant mixing and dilution would take place before water reaches the off-take. Organic matter A high-risk source of organic matter is the Wall Flat irrigation area discharge near the Wall Flat township off-take. Other flood-irrigation area discharges from Cowirra, Toora, Mypolonga and Pompoota irrigation areas were considered to pose a moderate risk. Risk management options (eg treatment plants) are being explored by SA Water for all these supplies. The stormwater discharge from the Berryman Avenue catchment, Mannum poses a high risk (during rainfall events) to the Mannum supply off-take (see Kinhill 1999 for catchment maps). The other Mannum stormwater discharges pose a moderate risk, as do the vessel mooring areas (Mannum foreshore/Murray Princess, Riverlane, Unforgettable Houseboats) that are in close proximity. Other lower risk sources include wetlands and several septic tank waste disposal systems located on the floodplain of the river. Nutrients A high-risk nutrient hazard was attributed to rainfall event discharge from the Cowirra irrigation area due to a substantial increase in the likelihood that stressors would reach the Cowirra and Mannum offtakes. Rainfall event discharges from Wall Flat, Toora, Mypolonga and Pompoota irrigation areas were considered to pose a moderate risk. It is unlikely that these higher level nutrient risks would immediately cause an algal bloom that would affect a water supply off-take as other causes and conditions (eg suitable light and temperature) need to be present. These links and process affecting nutrients need to be explored in more detail for the areas surrounding the off-takes. Informal camping areas (Wall Flat and Mypolonga) and Mannum vessel/houseboat mooring areas also received a moderate risk ranking due to the reasons noted above. Most other nutrient risks were assessed as low level, from sources such as wetlands, stormwater, houseboat/vessel discharges, landfill and septic tank effluent discharges. Turbidity Event discharges from several of the flood-irrigated areas posed moderate turbidity risks. As discussed earlier for the aquatic ecosystem environmental value, the surrounding highland and dairy yard areas 171
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E N V I R O N M E N T P R O T E C T
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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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2 Renmark to border LAP area assessment - EPA - Sa.gov.au

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