The State Government will need to find hundreds of extra gigalitres of water a year under plans to develop agricultural land and a sugar industry on the Ord River irrigation scheme.
The Ord surface water allocation plan released yesterday shows water demand will rise from 230-350gl a year to 608-1070gl if the land available for farming grows from 16,000ha to more than 50,000ha.
Chinese-backed company Kimberley Agricultural Investments has started work to develop a sugar industry and state-of-the-art mill with co-generation capacity as part of an investment which could top $1.5 billion.
However, KAI has always said the project depends on extending the irrigation scheme across the border into the Northern Territory to create enough farmland to supply the mill.
KAI is already clearing land after the Government named it as the preferred developer of 13,400ha released as part of the second stage of the Ord scheme.
The water allocation plan said up to 275gl a year was needed to grow sugar cane on the Knox Plain and Goomig land.
Another 140-270gl is earmarked for land in the NT , but the plan states this will be reviewed unless "additional supply options are developed".
One option being considered by the Government is building a barrier wall across one of four spillways leading off Lake Argyle at a cost of $80 million to increase capacity by 10 times the volume of Sydney Harbour - or about 5000gl.
Water Minister Terry Redman said the Ord River was one of Australia's most significant waterways and under increasing demand from irrigated agricultural and hydropower.
Mr Redman said increasing the capacity of Lake Argyle was a relatively low cost option to create a big increase in water supply.
He said the Government had set its sights on getting the most out the opportunities flowing from the Ord.However, it was far too soon to speculate on the likelihood of building the spillway barrier.