PIP: The water level of one of the longest rivers in the world, the Yangtze in China, fell 20 cm below sea level in February 1993 at Shashi in Hubei Province, the lowest water level in 20 years. In 1993, black-headed gulls left for their annual migration 3 months early because the deteriorating water environment in Dianchi Lake in Kunming, Yunnan Province, could not support them. China's total surface run-off is among the world's top 5. Yet it suffers a water deficit due to its large population size (88th in per capita water volume, 25% of the world average). No more than 650 million people would be the ideal population size for China's limited water resources. The urban water supply capacity increases 7% each year, but demand increases 10%. In 1992, 63% of the cities had water shortages. An expanding rural population has reclaimed land from lakes to produce food crops. China has an uneven distribution of water resources and rainfall. Many Chinese cities have drawn too much groundwater, causing land subsidence and declining groundwater levels. For example, the groundwater table in Xi' an has fallen more than 80 m in the last 40 years. The water situation is the leading obstacle to economic development in China. Large-scale water diversion projects are very expensive. It is imperative that China expand water resources by reducing waste and pollution. The Chinese parliament has passed 11 laws and decrees on water which resolve water disputes between provinces. Seepage and other flaws result in the loss of more than 50% of the water used in irrigated fields. China has introduced water-saving irrigation techniques (sprinkling and drip irrigation). Industry plans to recycle 15% of the water it uses, saving 5.25 billion cu.m annually. 63% of industrial waste water is treated before discharge, but individual factories dispose of the waste, polluting the water supply. Most of the treatment is not 2-stage treatment, though. Water conservation is of key importance for China.