@USBR August 24-Month Study Predicts Tier Zero for 2021 — @CAPArizona

Shown is Lake Mead’s location in the Colorado River Basin, Hoover Dam (the site where water elevations are measured) and water shortage tiers as determined by the 2007 Shortage Sharing Guidelines and the Drought Contingency Plan. Hoover Dam is iconic, so we recreating its massive intake tower to give visual perspective to the projected elevation in relation to the landmark. Equally as important was showing the natural slope of the lake to communicate that as elevation recedes, the amount of water is reduced, as well. Credit: Central Arizona Project

Here’s the release from the Central Arizona Project:

The U.S. Bureau of Reclamation has issued its August 24-Month Study. The purpose of this study is to project the year-end elevation of Lake Mead, which in turn determines the 2021 Lower Basin water supply conditions for CAP. BOR projects the Lake Mead elevation will be 1085.3’ on Jan. 1, 2021, which signals the Tier Zero supply of Colorado River water will continue for 2021.

Under Tier Zero, CAP’s water supply will be reduced by 192,000 acre-feet. This represents about a 12% reduction to CAP supplies. The Tier Zero reduction impacts CAP supplies previously available for underground storage, banking and replenishment. In addition, the reductions will likely reduce CAP agricultural uses by about 15%. While the word “reduction” is never popular, the fact that in 2021 Lake Mead will again operate in Tier Zero status shows that DCP is working to stabilize the reservoir from experiencing deeper shortages.

The August 24-Month Study also shows, in the most likely projection, continued Tier Zero conditions in 2022. However, due to hot and dry conditions across the Colorado River basin, the risk of a deeper reduction under Tier One shortage has increased for 2022. The reductions under Tier One are almost three times larger than Tier Zero. But thanks to the continued hard work across the Arizona water community, including the mitigation programs implemented through the Arizona DCP framework, we are prepared to manage Tier One reductions if they occur.

Hoover Dam from the Arizona side. Photo credit: Allen Best/The Mountain Town News

Here’s the release from the Arizona Department of Water Resources:

The United States Bureau of Reclamation (Reclamation) has released its August 24 Month Study, which projects Colorado River operations for the next two years. The study projects the operating conditions of the Colorado River system, as well as runoff and reservoir conditions. The Upper Basin experienced around average snowpack (107%) this year, and the April-July inflow into Lake Powell came in at 52% of average. The below-average projection was due to extremely hot and dry conditions in the Upper Basin during the spring and summer of 2020. Consistent with the 2007 Interim Guidelines, Lake Powell will operate under an annual release of 8.23 million acre-feet in water year 2021 with a potential of an April adjustment up to 9.0 million acre-feet.

The August 24 Month Study projects Lake Mead’s January 1, 2021 elevation to be 1085.28 feet, putting Lake Mead in a Tier Zero condition for 2021. The Study also projects a Tier Zero condition for Lake Mead in 2022 with the projected January 1, 2022 elevation of 1086.90 feet. Tier Zero conditions require a 192,000 acre-foot reduction in Arizona’s 2.8 million acre-foot allocation. The Lower Colorado River Basin is in Tier Zero for 2020. The August 24 month study projects that the Lower Colorado River Basin will remain in the Tier Zero condition in 2021.

“This is more evidence that the Drought Contingency Plan that was approved by the Arizona Legislature and signed by Governor Ducey in early 2019 was a success,” said Tom Buschatzke, Director of the Arizona Department of Water Resources.

“Its implementation offsets potentially deeper cuts in Arizona’s Colorado River allocation beyond the 192,000 acre-feet that the State annually has stored in Lake Mead for several years.”

These reductions will fall entirely on Central Arizona Project (CAP) supplies, impacting CAP supplies for water banking, replenishment and agricultural users. The Tier Zero reductions will not impact tribal or municipal CAP water users.

While the Tier Zero reductions are significant, they are part of broader efforts being implemented to reduce the near-term risks of deeper reductions to Arizona’s Colorado River supplies. In addition to the Tier Zero reductions to CAP supplies, other programs to conserve and store water are being implemented in Arizona.

These include programs with the Colorado River Indian Tribes, Gila River Indian Community, the Arizona Department of Water Resources (ADWR), and the Central Arizona Water Conservation District (CAWCD), as well as Reclamation. Including the 192,000 acre-foot allocation reduction, Arizona entities conserved a total of 385,000 acre-feet in Lake Mead in 2020.

The August 24 Month Study shows that in the near term, the programs being implemented in Arizona and across the Colorado River system, along with favorable hydrology, have helped avoid a near-term crisis in the Colorado River system. However, we continue to face significant near-term and long-term risks to Arizona’s Colorado River supplies. We have much more work to do to address our shared risks. ADWR and CAWCD have jointly convened Arizona water stakeholders to address these risks and to prepare for new negotiations regarding the long-term operating rules on the Colorado River.

The construction of Hoover Dam created Lake Mead in 1935, which serves as the primary storage reservoir in the lower Colorado River Basin. Water levels in Mead have declined significantly since 2000 when the reservoir peaked at more than 1,200 feet above sea level. As of October 2019, the reservoir is less than 40 percent full at just over 1,080 feet above sea level. Credit: Jirka Matousek / Flickr via Water Education Colorado

from The Associated Press (Sam Metz):

The white rings that wrap around two massive lakes in the U.S. West are a stark reminder of how water levels are dropping and a warning that the 40 million people who rely on the Colorado River face a much drier future.

Amid prolonged drought and climate change in a region that’s only getting thirstier, when that reckoning will arrive — and how much time remains to prepare for it — is still a guess.

The U.S. Bureau of Reclamation released projections Friday that suggest Lake Powell and Lake Mead will dip 16 feet (5 meters) and 5 feet (1.5 meters), respectively, in January from levels recorded a year earlier. Despite the dip, Lake Mead would stay above the threshold that triggers severe water cuts to cities and farms, giving officials throughout the Southwest more time to prepare for the future when the flow will slow.

“It’s at least a couple of decades until we’re saying, ‘We don’t have one more drop for the next person that comes here,’” said Ted Cooke, general manager of Central Arizona Project, the canal system that delivers river water. “But people certainly ought to be aware that water — the importation of a scarce commodity into a desert environment — is expensive and, with climate change, going to get even more expensive.”

[…]

Last year, with increasingly less water flowing to Lake Mead and Lake Powell — the two largest man-made reservoirs in the United States — Arizona, California and Nevada agreed to a drought contingency plan that built in voluntary cuts to prevent the reservoirs from dropping to dangerous levels. The other states historically haven’t used their full allocation of water and focus on keeping Lake Powell full enough to generate hydropower.

Nevada and Arizona will make those voluntary cuts under the new projections, which they also made last year for the first time. But because neither state is using its full share of water, the impact has been minimal and hasn’t trickled down to homes. Mexico also is facing another round of cuts.

Lake Mead’s expected level of 1,089 feet (332 meters) is almost identical to last year’s projections because conservation efforts and a snowy winter prevented an expected drop, said Michael Bernardo, Bureau of Reclamation river operations manager. The wet weather didn’t last, prompting engineers to forecast the lakes will keep receding.

When projections drop below 1,075 feet (328 meters), Nevada and Arizona will face deeper cuts mandated by agreements between the seven states and Mexico.

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