water use in southwest heads for day of reckoning

NYTimes | Barring a sudden end to the Southwest’s 11-year drought, the distribution of the river’s dwindling bounty is likely to be reordered as early as next year because the flow of water cannot keep pace with the region’s demands.

For the first time, federal estimates issued in August indicate that Lake Mead, the heart of the lower Colorado basin’s water system — irrigating lettuce, onions and wheat in reclaimed corners of the Sonoran Desert, and lawns and golf courses from Las Vegas to Los Angeles — could drop below a crucial demarcation line of 1,075 feet.

If it does, that will set in motion a temporary distribution plan approved in 2007 by the seven states with claims to the river and by the federal Bureau of Reclamation, and water deliveries to Arizona and Nevada would be reduced.

This could mean more dry lawns, shorter showers and fallow fields in those states, although conservation efforts might help them adjust to the cutbacks. California, which has first call on the Colorado River flows in the lower basin, would not be affected.

But the operating plan also lays out a proposal to prevent Lake Mead from dropping below the trigger point. It allows water managers to send 40 percent more water than usual downstream to Lake Mead from Lake Powell in Utah, the river’s other big reservoir, which now contains about 50 percent more water than Lake Mead.

In that case, the shortage declaration would be avoided and Lake Mead’s levels restored to 1,100 feet or so.

Lake Powell, fed by rain and snowmelt that create the Colorado and tributaries, has risen more than 60 feet from a 2004 low because the upper basin states, Colorado, New Mexico, Wyoming and Utah, do not use their full allocations. The upper basin provides a minimum annual flow of 8.23 million acre feet to Arizona, Nevada and California. (An acre-foot of water is generally considered the amount two families of four use annually.)