China faces a growing shortage of water which will hit farmers, affect living standards and force a steep rise in grain imports in the medium term, according to Lester Brown, the US economist who created a stir three years ago with a stark warning about the ability of the world's most populous nation to feed itself. The new study focus debate on water, a hitherto neglected issue which he says is "a political tightrope" for the government in Beijing. Written joinlty with Brian Halweil at the Washington-based Worldwatch Institute of which he is president, the study is to be published in the summer.