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Biggest inflows in 25 years on the way

Friday, 14th January, 2011

By Gina Wilson

Homes in Menindee are likely to be flooded as the biggest inflows in a quarter of a century force as much as 40,000 megalitres per day into the Menindee Lakes.

The massive inflows will come from three large downpours in northern NSW and Qld, including this week's deadly floods, and will combine with water from local rain to push the inflows way beyond their current level.

While releases from the lakes will next week increase to 26,000mL/d, that figure would be dwarfed as new floodwaters surge into the system.

The Office of Water's surface water management manager, Paul Simpson, said early estimates were that at its peak, due by late next month or early March, between 30,000 and 40,000mL/d will flow into the Menindee Lakes.

"The river system is full," Mr Simpson said. "Heavy rain and flooding is continuing in the upstream catchments and local rainfall events continue to increase river flows and the volumes that will pass into the Menindee Lakes and into the Lower Darling River."

Mr Simpson said flood flows from widespread rain in the north of NSW in November and December were making their way through the Barwon-Darling

River system and were expected to arrive at the Menindee Lakes at the end of this month and early into February.

A new flush of water, from major flooding in the Condamine- Balonne River system in southern Queensland, will also make its way down the Barwon-Darling, arriving in Menindee about mid-March.

"Further, in the past few days torrential rainfall and more widespread flooding has occurred in southern Queensland, including the Condamine-Balonne, Intersecting Streams and Border Rivers," Mr Simpson said.

"While it is too early to predict with confidence the flows that will enter the Barwon-Darling from these systems, it is likely to rank with some of the highest inflows in the past 25 years.

"This is expected to extend the duration of high flows reaching the Menindee Lakes and increase the peak flows." 

Next week's increased flows were needed to reduce the number of houses affected when the river finally peaked in six to eight weeks' time, with more increases likely, Mr Simpson said.

"Depending on the updated flow forecasts at that time, it is expected that releases will have to be increase, which unfortunately may inundate some houses and further reduce access to properties," he said. 

"It is also likely that there may be further increases in releases in the weeks to come."

The NSW Office of Water said it was working with State Water Corporation to manage "releases from the Menindee Lakes to the Lower Darling River and Great Anabranch to minimise flooding of dwellings around Menindee, maximising environmental benefits downstream and making sure that the lakes are full when the flooding passes."

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