Binningup plant buys time

The state government’s proposed desalination plant at Binningup is expected to provide at least 45 gigalitres a year to the integrated water supply scheme by the end of 2011.

Further expansions to the project are expected to take the total water provided to 100GL – or 100 billion litres – a year for schemes in Perth, the Mid-West and the Goldfields.

Costing $640 million, with an additional $315 million to be spent on integration, the desalination plant will replace tapping the South West Yarragadee aquifer as the preferred option for the short-term relief of the state’s water needs.

According to the Water Corpora-tion’s State Water Plan 2007, water use in Western Australia has tripled over the past 25 years, to an estimated 2,340GL in 2005.

Of that, about 1,690GL – or 72 per cent – comes from groundwater sources, with much of the remainder coming from surface water sources, such as rivers and dams.

About 18 per cent of that water is used by households, with 37 per cent going to the agriculture sector, 26 per cent to the minerals and energy sectors, and a further 16 per cent used by other commerce and industry.

While the study indicated that 11,515GL could be taken sustainably from existing sources, the impact of climate change on those estimates had not been made.

Despite this, the water plan indicated the amount of water in annual rainfall had decreased by 10 per cent, and winter rainfall by 15 per cent, during the past 35 years, which it says has resulted in an average 50 per cent decrease in flows to public water supply dams.

On top of current water production levels, Water Corporation studies say WA will need to find a further 107GL to maintain water security, to be partially assisted through catchment management and a water re-use project.

Even with the forecast 90GL from the Kwinana and Binningup desalination plants, and an additional 17GL sourced from trading with Harvey Water, the corporation predicts further water sources will be required by 2015.

To that end, the government has refused to rule out its earlier plan of tapping into the Yarragadee aquifer, or further use of groundwater reserves.

Statistics released by the office of Premier Alan Carpenter show up to 13.6 per cent of water across the state is recycled, with the government on track to reach a target of 20 per cent by 2012.

At the same time, total scheme water usage has dropped from 185 kilolitres per person in 2001 to 153kL in 2007.

While the state’s population has grown by more than 140,000 in that period, the figures still represent a saving of around 40GL per year.

However, these changes won’t be cheap, with the state government predicting an increase of around $30 in the average household water bill in 2008-09 to help fund the plant, coming after the $28 rise announced for the 2007-08 financial year.