DENVER, Dec. 20 (UPI) -- Seven thirsty western states and 10 tribal authorities that depend on the waters of the Colorado River have an extra year to hammer out an agreement to apportion water use for the next half century.
At a meeting of the Colorado River Water Users Association in Las Vegas last week, federal officials accepted a drought contingency plan crafted this summer that will jump start voluntary conservation efforts by states and Mexico in the lower Colorado River basin beginning Jan. 1.
Nevada, Arizona and Mexico, which all drain water below Lee's Ferry, in Marble Canyon, Ariz., have agreed to pull back water use. For the first time, California, which has a prior water right by law, has agreed to curtail water use if Lake Mead's elevation drops significantly further.
In 2026, the multistate Colorado River Compact will get its first makeover since 1999 to account for the effects of climate change, drought, population growth and agriculture.
U.S. Secretary of the Interior David Burnhardt told state water managers that the federal water reclamation bureau will immediately begin its review of the official river water apportionment plan, instead of waiting until the end of 2020.
Flows 1,450 miles
The Colorado River flows 1,450 miles, starting in the high mountains in Colorado's western slope and ending as a sandy trickle, 100 miles from the Gulf of Mexico. On the way, the river is dammed and diverted, pumped through hydroelectric plants and pushed through tunnels and man-made canals.
States in the river's upper basin -- Wyoming, Colorado, Utah and New Mexico -- use half as much water as the 40 million people and winter-vegetable growing farms in the lower basin, on the other side of the Hoover Dam.
That imbalance and the effects of a 20-year drought are visible on the shoreline of Lake Mead, where a high-water mineral bathtub ring shows how far the lake's elevation has dropped.
Under rules set in 1922, the upper-basin states must deliver a fixed 7.5 million acre feet of water annually, but it's those states that bear most of the risk of climate change and dropping river flow, said Colorado River expert and author John Fleck, who teaches water policy at University of New Mexico.
Politicians over-appropriated the water in the river in the 20th-century boom to create dams and canals in the Southwest. These water diversions helped develop the booming cities of Los Angeles, San Diego and San Bernardino in southern California, Tucson and Phoenix in Arizona and Las Vegas, Fleck said.
But as years get drier, those bad calculations threaten the water supplies of millions of people.
"They ignored the scientists who were saying there was less water in the river and overestimated. Now we're paying the price," he said.
Some climate-change estimates in recent studies show as much as 25 percent less water in the river by 2050 as water evaporates or is absorbed by thirsty riverbanks upstream.
Lowest flow in history
Water professionals in the Colorado River watershed got scared in 2002, the driest year in recorded history, when the river trickled to 25 percent of its usual flow, said John Entsminger, general manager of the Southern Nevada Water Authority.
By 2005, river water users faced a new drought reality and states squabbled and threatened to sue each other.
"That's when [Interior Secretary] Gail Norton laid down the gauntlet," Entsminger said. Federal regulators stepped in and offered to come up with water-shortage guidelines.
Since then, states have tried to work together.
Lower-basin cities have ramped up water conservation efforts. For example, Las Vegas pays residents $3 per square foot to replace grass lawns with water-friendly landscaping.
"Our population has increased by 46 percent -- more than 700,000 people have moved here -- but our water consumption has decreased by about 25 percent during the same time period," said Bronson Mack, a Southern Nevada Water Authority spokesperson.
Southern California cities also have drastically cut water use, drawing less from Lake Mead than ever before.
But the river flow problem won't disappear from conservation because 80 percent of Colorado River water is used in agriculture and industry, Entsminger said. Agriculture, even with water conservation practices, uses about 2.5 times as much water as the same land developed for residential use.
"No matter how efficient the cities are, they will not balance the books in the face of climate change," he said.
In the new drought plan, for years like this one when water in Lake Mead is below 1,090 feet sea-level in elevation, Nevada will curtail 3 percent of its water use and Arizona will cut back 7 percent. Mexico, which diverts river water at the Morales Dam on the border near Yuma, Ariz., will curtail water use by 41,000 acre feet.
If the elevation of Lake Mead drops by another 45 feet, California will hold off from using 200,000 acre feet of water, the agreement says.
At that point, the lake's levels would be so depressed that the Hoover Dam would stop generating electric power to millions of people in southern California because water levels would be too low to flow through it.
The new drought plan will buy time until states can determine how they deal with a new reality of apportioning less water going forward, Entsminger said.
"We're using the best available science and having frank discussions among water professionals," he said. "The basins are in a good place if we can keep operating in a cooperative manner across regional lines."