Colorado River basin: Releases from Lake Powell to Lake Mead are underway

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From (John Hollenhorst):

In recent weeks, the level of Lake Powell has been dropping sharply. The agency that controls the reservoir is releasing 11 billion gallons [33,757 acre-feet] of water each day to help bring up the level of Arizona’s Lake Mead. Lake Powell always comes down this time of year, but the releases now are significantly more than usual. “That level of release hasn’t occurred since the late ’90s,” said Richard Clayton, a hydraulic engineer for the U.S. Bureau of Reclamation. His job is to oversee releases from the Glen Canyon Dam. The high wintertime releases have triggered controversy. But the bureau has a message for boaters who worry Lake Powell might drop too far: “Don’t worry. Be happy.” The releases are prompted by expectations of the best spring runoff in more than a decade. Bureau experts predict, but can’t guarantee, that Lake Powell will eventually rise higher this summer than it did last year…

The release of water has caused Lake Powell to drop more than 13 feet, while Lake Mead has risen about 10 feet since early November. From a Nevada perspective, that’s good news. For a full decade, the big reservoir behind Hoover Dam has taken a battering from the region’s long-term drought. Lake Mead is currently about 42 percent full, and its surface area has shrunk drastically. Lake Powell currently stands about 57 percent full. This year, a new agreement reached by the seven states on the Colorado River will likely require additional releases from Lake Powell to Lake Mead. If spring runoff is high enough to trigger the so-called “equalization” agreement, it will require releases from Lake Powell sufficient to bring Lake Mead up to an elevation of 1,105 feet above sea level, according to Clayton. It currently stands at about 1,091 feet. “If we wait until April and don’t make appropriate changes to operations now,” Clayton said, “we won’t have enough time to release the required volume by the end of the water year.”

More coverage from The Arizona Daily Star (Pat Jacobs/Sharon Megdal/Warren Tenney/Carol Zimmerman). From the article:

Each year, the secretary of the interior looks at river flows and the expected water levels in Lake Mead and Lake Powell. Using this information, the secretary will declare the river water supplies are normal, in surplus, or in shortage. The key factor in the decision is the amount of storage (as measured by water elevation above sea level) in Lake Mead. Last year, Lake Mead at its lowest was only seven feet above the shortage trigger point of 1075 feet (it’s risen about eight feet since then). If a shortage is declared, Arizona and specifically [the Central Arizona Project] would be the first to lose access to a portion of our Colorado River allotment. As part of the agreements with California, Nevada and the federal government which led to the construction of the CAP system, Arizona consented to junior (lowest) priority to Colorado River water.

It’s important to note that even if levels in Lake Mead were to drop to 1,025 feet (a Level 3 shortage), Tucson and the other cities using CAP water would not lose access to any of their allocations. Municipalities and Native Americans have the highest priority rights to CAP water.

More Colorado River basin coverage here.

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