Statistics show that the total discharge of waste or polluted water in China was 33.6 billion ton in 1991. A 70% share of this amount belongs to industrial effluent, more than half of which does not meet discharge standards. The rest, 30% is domestic sewage, for which the proper disposal rate is less than even 10%. Of more than 1,200 rivers in the country, 850 have already been polluted, and all the seven major flows are contaminated at different levels. Such a further decrease of usable water resources has been dramatically increased the imbalance between demand for and supply of water.
The development and utilization of Chinese water resources has a long history, including the legend of the DaYu Riparian Works. The Dujiangyan Dam, built by those led by Li Bing and son in the year 251, is still functioning today. Again, the famous Great Canal was opened in 486. Ceaseless wars and diminished human capability of controlling nature resulted in frequent flood and drought damage. A history book records 1,500 breakdowns of dikes in 2,000 years to 1949 plus 26 major diversions of river courses.
From 1949 to the mid 1990s, China has carried out a number of water works, and made brilliant achievements in water-work constructions. To give some major examples, it constructed a total of nearly 200,000 kilometers of dikes and sea-banks, and 8,600 various kinds of dams. Most well-known are the Changjiang water-power stations at the Gezhouba Dam and the Huang He water-power station at the Longyangxia Valley. The total capacity of these dams amounts to 460 billion cubic meters, 80% of which is used for agricultural irrigation. In the northern arid areas, over 3 million electric-powered wells have been dug. These irrigation facilities provide the agricultural sector with 45 million cubic meters of water, making 49 million hectares of farmlands effective for irrigation. Among those farmlands, no less than a 32 million hectares endured drought and flood damage, and now ensures good harvests. Fundamentally, the country has brought under its control the Huang He, which used to flood frequently, and secured agricultural production and human lives in the basin from any breakdown of dikes since 1949.
