由于工农业生产的不断发展和人口平均需水量的增加,世界各国对水的需要量急剧增长,尤其近年来普遍出现严重干旱,致使许多国家和地区缺水的问题越来越突出。如美国1950—1975年的25年内,总引水量由2,800亿立米增至4,980亿立米,其中工矿 Due to the continuous development of industrial and agricultural production and the increase of the average water demand of the population, the water demand in various countries in the world has risen sharply. In particular, the severe drought in recent years has caused the issue of water shortage in many countries and regions to become increasingly prominent. For example, in the 25 years from 1950 to 1975, the total water diversion in the United States increased from 280 billion cubic meters to 498 billion cubic meters,