从历史上来讲,远距离大规模调水,是为了支持干旱及半干旱地区的发展而出现的,或为了促进这些地区的生产而采用的。在美国各州城市化的过程里,出现了许多这样的工程项目,其中大多数常常是用来支持干旱和半干旱的西部各州的城市与灌溉农业的发展的。这些干旱地区的主要州—加利福尼亚州,正象可以予料到的那样,大规模调水工程已经达到其顶峰了。 Historically speaking, large-scale water diversion over long distances has emerged to support the development of arid and semi-arid areas or to promote production in these areas. In the process of urbanization in the states of the United States, many such projects have emerged, the majority of which are often used to support the development of urban and irrigated agriculture in arid and semi-arid western states. As can be expected, the major state in these drylands, California, has reached its peak.