All three rivers feeding China's Northern Plain are severely polluted, damaging health and limiting irrigation. The lower reaches of the Yellow river, which feeds China's most important farming region, ran dry for 226 days in 1997. Northern China is home to two thirds of the country's cropland but only one fifth of its water. As competing demands for water are made by cities, industry and agriculture, the land is drying up. Between 1991 and 1996, the water table beneath the north China plain fell by an average of 1.5 metres a year.
Settlers have long dreamt of finding a way to turn coastal rivers inland.
But an ambitious scheme to reverse the flow of the Snowy River has backfired disastrously, threatening to deprive Adelaide of fresh water. The region that the diverted Snowy River now feeds is bounded by Australia's two longest rivers, the Murray and the Darling. The water tables under this land are now rising, pushing deadly quantities of salt to the surface. The salt has already destroyed some of the country's most productive farmland. Many of the basin's tributaries may be unusable for irrigation in 20 years time, let alone as a source of drinking water.