Western States Face Tough Choices Over Water Supply

 Lake Mead and Hoover Dam

In the water battle between rural and urban interests, it looks like a century of western water law will have to give way to political reason, and farmers will end up losing.  But it will be an ugly fight.  Here's Michael Hiltzik describing the central issue on the Colorado River:

A quick history lesson: The Colorado Compact, reached by six of the seven basin states in 1922 under then-Commerce Secretary Herbert Hoover, aimed to replace the tangle of state water allocation laws with a single legal regime in order to get the dam built. (Arizona finally signed the deal in 1944.) But the compact was based on a fraud — an estimate of river flows that Hoover and the states' negotiators almost certainly knew was wildly optimistic.
Many times, the compact has been revised and supplemented to meet changing conditions. In 1968, Congress authorized construction of the Central Arizona Project, a massive aqueduct serving Phoenix and Tucson, by passing the Colorado River Basin Project Act. Arizona agreed to be last in line for water from the Colorado if a serious drought struck.
The bill's drafters probably never thought supplies would become so tight. But the bill from nearly a century of overuse is on the verge of coming due. During the last 50 years, according to figures from the Reclamation Bureau, the population served by the river has grown from 12 million to 30 million. Over that period, the average flow on the river has fallen from 15.5 million acre-feet to as low as 12 million. (An acre-foot serves two households a year.)
The river's apparent abundance has encouraged exceptionally wasteful usage. For example, thirsty forage crops such as alfalfa and pasture land account for as much as half the irrigated acreage in California, according to a report last year by the Pacific Institute. And as my colleague David Pierson reported recently, much of the harvest is shipped to China.
The Pacific Institute finds that stingier but still effective irrigation practices could save nearly 1 million acre-feet a year throughout the Colorado basin, and replacing alfalfa with cotton and wheat would save 250,000 acre-feet. But plainly, a trade pattern that effectively exports the West's scarce water to China isn't sustainable.

The article mentions that draining Lake Powell is being discussed as a real possibility.  That shows how much rethinking is going on out there. Unchecked urban growth, combined with massively subsidized irrigation practices in agricultural production are going to blow up western water law.  It is politically infeasible to continue allowing agriculture nearly unfettered access to ridiculously cheap water while cities get thirsty.  Mother Nature is going to force a rethinking of urban growth and agriculture in the American Southwest.  I expect agriculture to be forced to give first, but urban growth will also slow to a crawl eventually.  It really makes no sense to work so hard to live in a place people never were intended to live in.