September 23, 2021

Drought Triggers Cuts to Arizona Water Supply

By Tim Linden

On August 16, in their annual report on the level of Hoover Dam’s Lake Mead, federal officials revealed that the water level has fallen to a point that automatically triggers cuts in Arizona’s water deliveries for 2022.

Arizona Department of Water Resources Director Tom Buschatzke told Western Grower & Shipper that the brunt of the impact of the 18 percent reduction (512,000 acre-feet) will be felt by Central Arizona farmers in Pinal County, who are mostly involved in field crop production as well as dairy farms and cattle ranches. There are few fresh produce crops grown in that region.

The Bureau of Reclamation measured the Lake Mead level at 1,068 feet, which is an all-time low since the dam was built in the 1930s and Lake Mead was formed and filled. In a 2019 drought contingency plan, California, Arizona, Nevada and Mexico agreed to take voluntary cutbacks in deliveries in an effort to maintain sufficient levels in Lake Mead. The agreement mandates cutbacks when specific water levels are reached. A level of 1,075 feet or less is the first trigger with Arizona taking the most damaging hit, as the Colorado River water reduction represents about 8 percent of the state’s water supply. Nevada loses 7 percent (21,00 A.F.) of its total take, while Mexico is reduced by 5 percent (80,000 A.F). California is not impacted at this Tier 1 level of cutbacks, but it will be impacted if Lake Mead continues to decline. Tier 2 reductions are triggered at 1050 feet, with Arizona losing an additional 80,000 A.F. to 592,000, and Nevada losing 4,000 more A.F. to 25,000. Once the Lake Mead level falls below 1,045 feet, California’s first reduction kicks in with a cutback of 200,000 A.F. under Tier 2b rules. Cutbacks increase significantly for California as the water level continues to drop below that.

The August 16 report projected Lake Mead’s water level for January 1, 2023, at a level above 1,050 feet, which predicts there will not be additional cutbacks until at least 2024. Buschatzke said a prediction of Tier 2 cuts in 2021 would also have triggered a provision of the agreement requiring California, Arizona, Nevada and federal officials to go back to the drawing table and discuss further measures to take to preserve the level of Lake Mead that allows for normal water deliveries.

The Arizona water expert said the trend in Lake Mead is not favorable as it has dropped more than 143 feet below its level of two decades ago. While some heavy precipitation years did see a rise in the level of Lake Mead, the overall graph is unmistakably heading down. Buschatzke said the precipitous drop this past year is due to an unprecedented below average runoff. While runoff from the snowpack in the mountains feeding the Colorado River typically is in the 70-80 percent range, this spring’s runoff was only 32 percent. Severe drought conditions throughout the West created the huge drop-off.

Though an overly wet year is always possible, the long-term trend points to the need for other solutions.

In 2022, Buschatzke said Central Arizona will not receive sufficient deliveries from the Colorado River to recharge ground water supplies. He noted that once the Tier 1 cutbacks are triggered, there is no going back regardless of what happens over the next four months. He said water users and water suppliers need to have time to plan so the 2022 cutbacks are now written in stone.

Long-term, he said the three lower Colorado River basin states are searching for additional water sources. Projects that have been discussed and studied to some extent include buying water currently allocated to Native American Reservation land, building a desalinization plant near the Sea of Cortez in Mexico, increased use of reclaimed water in Las Vegas, and diverting water from the Mississippi and/or the Missouri rivers to western states. All of these potential water sources come with a myriad of issues but it appears likely that a combination of these and other ideas will be necessary sooner rather than later.