A shortage of water at Lake Mead would cut flows for the Central Arizona Project by at least 20 percent.

Ron Medvescek / Arizona Daily Star 2015

Longer-range outlooks for Lake Mead and the Central Arizona Project are increasingly grim due to this year’s bad runoff, the U.S. Bureau of Reclamation said Wednesday.

The result is that the bureau is pushing hard for states in both the Upper and Lower Basins of the Colorado River to reach agreement this year on drought planning to ease the pain of future shortages, after negotiations have so far failed.

The bureau’s new forecast for the river shows that the chance of a CAP shortage next year is almost nil, but in 2020, it’s over 50 percent. Looking farther ahead, the chances of a shortage for 2021 through 2023 exceed 60 percent each year, the bureau said. The CAP provides drinking water to Tucson and Phoenix.

The gloomy forecasts are based on this year’s expected poor spring-summer runoff into Lake Powell at the Utah border from the Upper Basin states of Colorado, Wyoming, Utah and New Mexico. The most recent forecast, last week, was 42 percent of average runoff.

This year “has brought record-low snowpack levels to many locations in the Colorado River Basin, making this the driest 19-year period on record,” the bureau said in a news release announcing the new forecasts. “With drought and low runoff conditions dating back to 2000, this current period is one of the worst drought cycles over the past 1,200 plus years.”

Specifically, the bureau predicted:

  • A 52 percent risk of a 2020 shortage.
  • Shortage odds of 64 to 68 percent in 2021, 2022 and 2023.

The most likely shortage would cut CAP deliveries by about 20 percent. Those cuts would mainly slice water supplies to Central Arizona farmers and the Arizona Water Bank, a state program that recharges Colorado River water. Such a shortage will occur when Lake Mead drops below 1,075 feet at the end of a given year.

Cuts would likely also affect the Central Arizona Groundwater Replenishment District, a related agency to CAP that buys and recharges river water into the ground to compensate for groundwater pumping that serves new suburban development.

  • Starting in 2021, the odds are more than 20 percent of Arizona facing a more severe shortage, in which it would lose about 26 percent of its CAP water. That shortage would happen when Lake Mead drops to between 1,050 feet and 1,025 feet.

Lake Mead sat at nearly 1,085 feet elevation at the end of April. It’s expected to drop to 1,079 feet by the end of December.

If the lake drops below 1,075, Mexico and Nevada would also stand to lose some of their Colorado River water deliveries, but by a far smaller percentage than Arizona would lose of their total allocations of river water. Nevada would lose 13,000 acre-feet, or 4.3 percent of its total share. Mexico would lose 50,000 acre-feet, or 3.3 percent.

The Lower Basin Drought Contingency Plan would require Arizona, Nevada and California to reduce their use of river water more than already required when the first shortages hit. The plan’s purpose is to prevent Lake Mead from dropping to catastrophically low levels over the coming decade.

The plan’s approval has been delayed significantly. That’s in large part because of conflicts between the CAP and the Arizona Department of Water Resources over how this state’s share of the river’s water should be managed and who should manage it.

The state water department and Gov. Doug Ducey tried to get the Legislature to pass bills this year to make conservation for the plan easier, but the Legislature didn’t go along.

Last week, representatives of the three Lower Basin states met in Las Vegas to discuss river issues. At the meeting, Reclamation Commissioner Brenda Burman sought to get the CAP and the state water department to meet and settle their dispute, said Sally Lee, an ADWR spokeswoman, and Bart Fisher, chairman of the Colorado River Board of California.

A Bureau of Reclamation spokeswoman, Patti Aaron, said that isn’t her understanding of what happened at the meeting. But in the bureau’s news release, Burman issued an emphatic plea for the drought plan.

“We need action and we need it now. We can’t afford to wait for a crisis before we implement drought contingency plans,” Burman said. “We all — states, tribes, water districts, nongovernmental organizations — have an obligation and responsibility to work together to meet the needs of over 40 million people who depend on reliable water and power from the Colorado River.”

After last week’s meeting, the Arizona water department and CAP issued a joint statement saying they’re committed to getting the drought plan worked out in Arizona “by addressing a broad range of issues” respecting concerns of all interest groups involved. The two have begun discussing the plan again after more than a year of open conflict, they said.

The Arizona water department and officials from the other six river basin states issued statements accompanying the bureau news release emphasizing the drought plan’s importance. A number of environmental groups issued similar statements later Wednesday.

Thursday morning, CAP issued a detailed statement on the bureau's forecast, again stressing its commitment to completing the drought contingency plan. It has recently drawn sharp criticism from Upper Basin state water officials and the Arizona water department for its resistance to some conservation measures and been accused, unfairly, CAP says, of manipulating operations of the river's reservoirs to get more water for itself

"CAP has long recognized that the Colorado River system is vulnerable to poor hydrology and we’re experiencing that now. The bureau's data set supports that. We have been working with our partners to take proactive actions to decrease the risk in the system," the statement said.

The Associated Press contributed to this story.

Contact reporter Tony Davis at tdavis@tucson.com or 806-7746. On Twitter@tonydavis987