Wednesday, August 21, 2013

Dwindling Colorado River Forces First-Ever Cuts in Lake Powell Water Releases

More than a dozen years of drought have begun to extract a heavy toll from water supplies in the West, where a report released last week forecast dramatic cuts next year in releases between the two main reservoirs on the Colorado River, the primary source of water for tens of millions of people across seven western states.

After studying the problems facing the river for the past two years, the U.S. Bureau of Reclamation – the agency charged with managing water in the West – announced Friday that it would cut the amount of water released next year by Lake Powell in Arizona by 750,000 acre-feet, enough to supply about 1.5 million homes.

It marks the first reduction in water flows since the mid 1960s, when the lake was created by the construction of Glen Canyon Dam. "This is the worst 14-year drought period in the last hundred years," said Larry Wolkoviak, director of the bureau's Upper Colorado Region.

The move could trigger an "unprecedented water crisis within the next few years," the business coalition group Protect the Flows told USA Today, as reductions could have major ramifications for farmers and businesses downstream that depend on those flows, as well as on hydroelectric power generation.

"The river is already severely endangered due to way too many dams and diversions," Gary Wockner of told National Geographic, noting the impact the reduced flows also would have on fish and wildlife throughout the Grand Canyon. "The impact on the health of the Colorado River is unsustainable."

It's difficult to overstate how important the Colorado River is to the West. From Lake Powell along the Arizona-Utah border, the river flows more than 300 miles through the Grand Canyon to Lake Mead in Nevada, supplying drinking water to more than 36 million people in Arizona, California, Colorado, New Mexico, Nevada, Wyoming and Utah.

The river also supplies water to 22 native American tribes, 11 national parks, 7 national wildlife refuges, and 4 million acres of farmland, ThinkProgress reports.

At Lake Mead, water levels will lower by 8 feet as a result of the reduction, after the lake already has dropped by about 100 feet since the current drought began in 2000, the Wall Street Journal notes. That would bring water levels there – now about 1,105 feet – within striking range of 1,075 feet, considered the threshold for the U.S. Department of the Interior to declare a water shortage.

Lake Mead

Today, Lake Powell is only about 45 percent of its full capacity while Lake Mead stands at 47 percent full, according to Chuck Collum of the Central Arizona Project (CAP), which delivers water from the Colorado River to central and southern Arizona.

He told USA Today that the forecast would mean CAP would see its water releases reduced by about 320,000 acre-feet, or a cut of about 20 percent. CAP says this will have no impact on the cities and Native American tribes it serves, however, because the reduction would impact largely underground storage and non-Indian agriculture.

For Las Vegas, which draws most of its water from Lake Mead and grew by more than 6,000 people a month in the 2000s, the extremely dry conditions of the past decade already have prompted a raft of water restrictions and conservation measures -- including banning grass front lawns in new home developments.

But the city isn't counting on conservation alone. If the conditions of the past several years continue indefinitely, by 2015 water levels at Lake Mead could drop below one of Las Vegas's two intakes there, imperiling the city's water supply. Today, its water authority is scrambling to build a third intake to allow it to draw water at levels below 1,000 feet -- an insurance policy if the lake's levels drop low enough to put its first intake out of service.

(MORE: 20 Cities That Could Run Out of Water)

"It's essentially a race for us," Scott Huntley of the Southern Nevada Water Authority told National Geographic, because the lake likely "is going to drop more precipitously than seen in the past."

At their root, the potential water shortages both lakes face is the result of what has happened to theColorado River over the past decade. Long-running drought across the Southwest has starved the river to its current low flows, and climate change is expected to reduce them by 5 to 20 percent over the next 40 years, University of Colorado geoscientist Brad Udall told Smithsonian Magazine.

Its impacts will be felt at each stage of the river's development: less snowfall in the Rocky Mountains will mean less water enters the river at its start, while hotter air temperatures and drier weather will mean longer droughts and more water lost to evaporation. More