水是人类生活和生产不可缺少的一项资源。随着国民经济的发展,人口的不断增长,人民物质生活和文化生活水平的提高,人类对水资源的要求也不断增长。水虽是一种可以再生的自然资源,但其数量是有限的,不是取之不尽、用之不竭的。而且由于时空分布极不均衡,用水地区集中和用水量不断增长,以及水源污染,很多国 Water is an indispensable resource for human life and production. With the development of the national economy, population growth, the material and cultural life of the people, and the human demand for water resources are also on the rise. Although water is a renewable natural resource, its quantity is limited, not inexhaustible. Moreover, due to the extremely uneven distribution of time and space, the concentration of water-consuming areas and the growing use of water and the pollution of water sources, many countries