China's booming economy and rising population are causing a decline in the quality of the water in the nation's lakes. Pollution caused by eutrophication, a process that starves the water of oxygen, is one of the most pressing issues for the nation's environmentalists.

The major river systems show the scale of the problem. Nearly 10 percent of surface water is designated as being below Level V - "severely polluted" - while 24.6 percent of the most important lakes (most of which are reservoirs) are in a state of eutrophication, resulting in the pollution of drinking water sources, according to the Action Plan for the Prevention and Treatment of Water Pollution, released by the Ministry of Environmental Protection in April.

In response, the central government has set a number of ambitious goals.