Published online 19 February 2009 | Nature | doi:10.1038/news.2009.111

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Updating farming practices key to hitting ambitious efficiency target.

Chinese farmers need to change the way they irrigate crops to help avoid drought. Punchstock

China must rapidly improve its outdated irrigation infrastructure if its ambitious plans to save water are to be realized, experts believe.

By 2020, China wants to reduce water-use per unit of gross domestic product (GDP) by 60%. The plan was announced last weekend – amid the country's worst drought for half a century – by the water-resources minister Chen Lei in the administration's annual national conference in Guilin, Guangxi province.

The move marks a shift in policy. China has, to date, focused on exploiting its water resources, but will now adopt a strategy of water-demand management that is based on making better use of water already mobilized, said Chen.

The ministry will also set out three "red lines" that will limit the total amount of water extraction and waste-water disposal, and increase the efficiency with which water is used.

"This is a very important strategic shift in water management," says Ma Jun, director of the Institute of Public and Environmental Affairs, a non-governmental organization in Beijing. "It is a step in the right direction," he adds.

Ma stresses, however, that myriad approaches needs to work in parallel to make fundamental changes in the situation – including sufficient financial backup, policies with clear incentives and sanctions, law enforcement, technological innovation, market mechanisms and public education.

Drying up

Official statistics show that China is short of 40 billion cubic metres of water a year on average: 300 million people are faced with drinking-water shortages and 15.3 million hectares of farmland – 13% of the country's total – are stricken by drought every year.

According to the Office of State Flood Control and Drought Relief Headquarters, the drought, which started in November, has affected 20 million hectares of crops nationwide – an increase of 58% compared with the previous year. This spring's wheat is the hardest hit.

To many, such as Gong Peng, an ecologist at the University of California in Berkeley, California and the Beijing-based Institute of Remote Sensing Applications, Chinese Academy of Sciences, the current crisis is symptomatic of the lack of sustainable water-management polices and proactive measures to tackle droughts. This is particularly the case with Chinese agriculture, which accounts for 70% of the country's water-use.

China's irrigation systems reach less than half of the total farmland. In Henan province, for instance, which is the most drought-stricken this spring, only a third of the farmed areas are properly irrigated.

Most of the irrigation systems in China were built in the 1950s and are poorly maintained. Moreover, most farmers use flood irrigation – where water is allowed to flood an entire field – a millennia-old practice that wastes a great deal of water.

Drop by drop

To meet the ambitious water-conservation target, "China must modernize its irrigation infrastructure and switch to drip irrigation," says Haim Gvirtzman, a hydrologist at Hebrew University in Jerusalem, Israel. Drip irrigation is by far the most water-efficient method of irrigation, whereby water is delivered at or near the root zone of plants, drop by drop, through an extensive web of tubing.

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"Switching to drip irrigation would help to save at least half of the water," says Gvirtzman. "It's cheaper in the long run, too." The level of water resources per person in Israel is only 12% of that in China, he adds. By using water more effectively – and by recycling 70% of its sewage water for agricultural irrigation – Israel gets by with the very limited water at its disposal.

Many believe that China also needs to have a long-term, systemic plan to restore its over-extracted groundwater. "In the North China Plain, you need to dig as deep as 300 metres in some areas to get fresh water – whereas a few decades ago, a couple of metres would normally do," says, Gong. According to Ma's book, China's Water Crisis1, more than half of the 60 billion cubic metres of unreplenishable, deep groundwater had been extracted in the region, creating a huge groundwater funnel with an area of 40,000 square metres.

The over-extraction of groundwater has decreased the run-off of many rivers – including the Yellow River, which has dried up in its lower reaches many times in the past decades, notably for 226 days in 1997. "Groundwater is the lifeline during prolonged droughts, when surface water disappears quickly," says Gong. "To restore and maintain groundwater at a safe level should be a paramount counter-drought measure," he adds.