All American Canal, California

This 80-mile-long canal brings water from the Colorado River to the citizens and agricultural industry of the Imperial Valley. The canal was completed in 1940, to replace a previous canal which served the same function, but traveled partly through Mexico (hence the name of the All American). The canal, one of the largest in the United States, travels through one of the hottest and driest places in the country, and is the sole source of water for the nation's fourth most productive, as well as most arid, agricultural region. In 2007, construction began on a 23-mile-long parallel lined canal, intended to reduce the approximately 67,700 acre-feet of annual seepage, which often resulted in flooding on the Mexican side of the canal, as well as depriving the Metropolitan Water District of Southern California of additional water. The project was completed in 2010.