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[BEIJING] The World Bank has urged China to adopt a technology that measures water use more accurately, encouraging farmers to prevent water wastage through evaporation.

The technology could form a vital part of China's bid to fight increasing water scarcity.

In their report 'Addressing China's Water Scarcity', released last month (12 January), the World Bank says that payments for water use should be based on evapotranspiration (ET) technology.

The technique uses data from satellite images to calculate the level of water lost by ET from a farmer's land.

It can therefore distinguish between water permanently taken out of the system through evaporation and transpiration — evaporation from plants — and water returned through irrigation for example.

Water management in China has not made such a distinction. Farmers must currently pay for whatever they have withdrawn, regardless of whether it is returned or not.

By charging them only for water lost through ET, it is hoped that farmers will be encouraged to take steps to prevent it.

"In water-scarce areas, ET technology is important to manage water resources," said Xie Jian, lead author of the report. "This approach encourages farmers to reduce the evaporation and transpiration that does not contribute to plant growth."

For example, Xie said, farmers can reduce evaporation by using species that require less water, reducing waterlogged areas, irrigating at times when evaporation is lowest — for example at night — using a covering of straw or plastic sheeting around plants to prevent excessive evaporation, and replacing open canals and ditches with pipes.

They might also reduce plant transpiration by using varieties tolerant to water stress and by weeding. Where excessive fertiliser and pesticide runoff is a problem, farmers will be encouraged to reduce pollution since they will be charged for water that is not reusable downstream. 

China is planning to launch a pilot ET project in the Hai River basin in northern China, with Beijing and Tianjin included in areas that will test the system to plan water resources.

Experts have repeatedly warned of a water crisis in China, particularly in the north of the country and in its capital, Beijing.

The shortage is set to reach a crisis point in 2010 when Beijing's population is expected to top 17 million — three million more than its resources can support.

Link to full World Bank report[12MB]