New Year’s Day marked a historic moment in the history of Western water wars — the first time the federal government exercised its right to decline California’s request for more than its allotted shared of water from the Colorado River. Thanks to the U.S. Interior Department, cities and agricultural areas in Southern California will lose about 650,000 acre-feet of river water this year, or enough to supply a city about the size of Los Angeles. The federal intervention is the result of the breakdown of a deal that was to have transferred water from farms to cities in Southern California. The Interior Department’s move marks a shift in water-use priority from agricultural areas to urban centers. It’s too early to predict the long-term effects of the shift, but in the short term, it will certainly put pressure on farmers to switch to less water-intensive crops and more efficient irrigation methods.