Water is a critical resource, and allocation is a political battle for its use. This problem has been occuring in the Southeast as well as the Southwest. The NYtimes writes about a 60-hour release of water to improve the fish environment in the Grand Canyon with an electricity cost of $30 - 35 million dollars to replace.

Torrent in Colorado River Is Unleashed to Aid Fish

Matt York/Associated Press
At the Glen Canyon Dam in Page, Ariz., water jetted into the Colorado River on Wednesday to benefit fish in the Grand Canyon.
The 60-hour release, being presided over by Interior Secretary Dirk Kempthorne, was the latest chapter in a long-running tug of war between the department’s Bureau of Reclamation, which controls the two major Colorado River dams, and the National Park Service over how to balance the Southwest’s need for hydroelectric power against the needs of an endangered fish, the humpbacked chub, for water flows that mimic the natural rhythms of the river.
The water poured out of the dam as if pumped through a gigantic fire hose, at the rate of 41,500 cubic feet per second — enough to fill the Empire State Building in 20 minutes. This release, which engineers call “high flow,” was meant to scour the river bottom and deposit silt and sediment to rebuild and extend sandbars and create new, calm backwater areas where the fish can spawn.