The Colorado River in Arizona is the major source of water...
..for the arid Southwestern United States and Northwestern Mexico. It is used to supply water to cities like Las Vegas, Los Angeles, Phoenix, and Tucson, all cities with burgeoning, growing populations. It is the major source of irrigation for the Imperial and Mexicali Valleys, which are two of the most fertile valleys in agricultural areas in western North America. And it's also used for a host of purposes.
The utilization of the river really didn't begin until early in this century when there were minor diversions and so on, but it really accelerated in the early 1930's with the completion of the Hoover Dam, which even though it has made settlement in population of the Southwestern United States possible, is probably, in the minds of some people, one of the greatest crimes against nature that's been committed in the 20th century. Of course, if any of you have ever spent a great deal of time in the Southwest and well, southern California or New Mexico but especially Southern Arizona, I think you'll begin to appreciate how truly harsh that environment is. And spending my time there, I sometimes wondered if we really should be living there at all, especially with the populations that we have.
Well, a lot of it is possible because of the Colorado River. The net result of all of this--well, there's two results. The first one is that the Colorado River is the most utilized river in the world. The second result, which is a direct consequence of this is that today not a single drop of the Colorado reaches the ocean anymore. Up until the 1960's some of the river still reached the ocean via a delta located at the very northern tip of the Gulf of California, but that has dwindled away and every drop is now stored and/or utilized by the United States and Mexico. We essentially lease a certain amount of water to Mexico from the Colorado every year based on international agreements.