Water Week

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Murray River salinity level rising above target – 800 EC for 95 per cent of the time; dilution flows allow control until 2008

Posted by waterweek on 26 September 2007

South Australia’s Minister for the River Murray, K.A. Maywald, gave the South Australian House of Assembly a short lesson on the ecology of the river and its flood plains on 11 September 2007.

Combination of factors kept salinity levels low: “In recent years, River Murray salinity levels at the border in South Australia have been very low, and this is because of the lower irrigation and the fact that most of South Australia’s water was coming from the head waters rather than the Darling as a consequence of the drought,” Maywald said. “Salt has also continued to build up on the flood plains. In addition, the effects of government programs, such as salt interception schemes and salinity zoning, have minimised impacts on the river. Salt interception schemes along the river currently remove more than 91,000 tonnes of salt per year that would otherwise enter the River Murray. This benefit translates to about a 500 EC reduction at Morgan — ‘EC’ is the term used for salinity measurement,” the Minister explained. “The target is to keep the salinity level below 800 ECs for 95 per cent of the time.”

Dilution flows check salinity until early 2008: “As I said,” Maywald continued, “low flows have resulted in relatively low salinity levels. However, continuous, extremely low flows, which we have experienced in recent times, are having the opposite effect and causing salinity to rise. As it is entering the River Murray, highly saline groundwater is not being flushed through. In recent months, as the flows have further reduced, salinity levels have begun to increase steadily. South Australia is currently tracking towards salinity peaking at about 1,000 ECs — or just above it — at Morgan around the beginning to mid October this year. Of course, the 800 EC is the target 95 per cent of the time. At current rates with the application of some dilution flow (which we have been able to negotiate under the new water-sharing arrangements that have been negotiated with the Murray-Darling Basin states under the provisions of the Murray Darling acts that each of those states have passed in their parliaments), the dilution flows will subside the salinity to around 600 EC to 800 EC in January 2008 before steadily starting to build again in 2008.”

Reference: Hon. K.A. Maywald, Minister for Water Security, House of Assembly, South Australia, 11 September 2007.

Erisk Net, 17/9/2007

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