二十世纪以来,全世界的城市与工业都有比较大的发展。1975年,百万人口以上的大城市,已发展到156个。城市规模的扩大,人口的迅速集中和增加,加之耗水量大的新兴工业的涌现,导致整个社会对水资源的需求量以惊人的速度增加。二十世纪初到七十年代中期,世界工业用水量增长了20倍。城市缺水问题已成为普遍关心的一个世界性问题。据统计,世界人口的增长率约为2%,而用水量的增长率达到4%,少数国家甚至高达10%。目前世界上已有四十多个国家缺水。我国的水资源并不丰富,人均占有量只有世界人均占有量的四分之一,加之降水时空分布不均匀,华北、西北地区水资源十分紧缺,水的供给已成为制约当地经济发展的重要因素。近二、三十年,我国的工业化、城市化发展迅速。1956年全国市级城市为200个(不含 Since the 20th century, cities and industries all over the world have made great progress. In 1975, the number of mega-cities with a population of over one million has grown to 156. The expansion of cities, the rapid population concentration and increase, combined with the emergence of new industries that consume large amounts of water, have led to an alarming increase in the demand for water resources from the entire society. From the early twentieth century to the mid-seventies, the world’s industrial water consumption increased by 20 times. The problem of urban water shortage has become a universal issue of universal concern. According to statistics, the world population growth rate of about 2%, while the water consumption growth rate reached 4%, even as few as 10% in a few countries. At present, more than 40 countries in the world have water shortages. China’s water resources are not rich, the per capita possession only a quarter of the world average per capita, combined with the uneven distribution of precipitation in time and space, water resources in North China and Northwest China are in short supply of water has become an important factor constraining the development of the local economy . Nearly two or three decades, China’s rapid development of industrialization and urbanization. In 1956 the city of 200 cities (excluding