Water shortage and contaminatiorChina is one of the 13 countries in the world withthe most limited water resources. The availableper capita volume of water is .2200 m3. only 25of the world average. In addition, water resource.are distributed unevenlyin China. About 44% ofthepopulation lives in the north but has access to onl.15% ofthe water resources. More than 6ow ofthe669 cities (of population >0.1 million) in China haveproblems with water shortages, and the situation in1l0 of those cities is categorized as serious (1). Inaddition, >24 million rural people have insufficiendrinking water supplies (2)
The water shortage will be exacerbated by serious pollution. More than 60% of China's largelakes are eutrophic (3), and the water quality hasdeclined in >50% of its rivers. The water quality at>50% of the monitored sections in five of China'seven largest rivers the Liaohe, Songhua, HaiheHuaihe, and Yellow rivers) is considered Grade IVolvorse in a five class grading svstem (3, 4)indicatingheavy pollution (Figure 1).The major concernsare ammonia nitrogen, biological oxygen demanc(BOD5), permanganate index, and oils (3).The dis
charge ofurban sewage and industrial wastewateris the main source of contamination in the rivers,as supported by the observation that >90% of theheavily polluted monitored sections are nearlargecities (3)
The use efficiencw of water is still low in ChinaIn 2000. the use efficiencies ofirrigationwater (thewater that reaches cultivated land and is availablefor plant erowth divided by the total amount of water obtained from the water source) and industriawater (the proportion of reused water relative to thetotal amount of water acquired for industrial usewere 0.43 and 0.55, respectively. In contrast, the ratios in developed countries have reached 0.70 and0.75-0.85, respectively (2). With ongoing develop-ment and urbanization, the gap between water supply and demand will become wider.
China's increasing water pollutionAlthough China is abundant in total water resources, it is still one of the 13 countries in the world with the most limited water resources. China now faces not only the problem of increasingly limited water resources, but also countless water pollution caused by the accelerated development of Chinese industry. Today, five of the seven major rivers in China have been found to be highly polluted. Coupled with the eutrophication of more than 60% of large lakes, a large amount of available fresh water is polluted, which in turn affects residents' daily life and sustainable economic development.
The main uses of water resources in China are concentrated in residents' daily water, agricultural irrigation water, industrial production water and so on. The gap between the supply and demand of water resources is further expanded due to the vast land area and the low efficiency of water resource utilization and the continuous development of urbanization