Lake Powell Surges 20 Feet

More than 20 feet. That is how much Lake Powell, the second-largest reservoir in the United States, has risen since hitting a low point in mid-September. The jump dwarfs the gains seen from this year's snowmelt and marks a sharp reversal for a water system that had fallen to record lows during a yearslong megadrought.

Storms in late October and early November sent heavy torrents through creeks that are typically small or dry. These floods overflowed banks and cut off access to several communities. Hundreds of people were ordered to evacuate their homes. Despite the local disruption, climate scientist Martin Hoerling of the University of Colorado, Boulder, said most of the water will feed depleted lakes and underground aquifers.

Hoerling described the influx as an unexpected boost from nature. Last winter's snowfall was weak and provided little relief when it melted in the spring and summer. The arrival of El Niño has intensified the heavy rain and flooding. Experts expect the phenomenon to last for several more months. This could further boost water supplies across the West, which relies on lakes, aquifers, and snowpack for storage.

As of Friday, Lake Powell remained just over a quarter full. Fifteen of its 17 boat launches were still unusable. Hoerling estimated that the floodwaters and additional rain could raise the lake along the Arizona-Utah border by a total of over 1.2 million acre-feet. That volume is enough to support around 4 million average families for a year.

Cities in the region reported some of their wettest weather in decades. In Pagosa Springs, Colorado, storms dumped about 7 inches of rain in October. Before the storms, more than 10,000 people in the town and surrounding areas were under water restrictions. Town manager David Harris noted that restaurants were encouraged to serve water only on request. Those restrictions are now lifted. Harris said the storm provided a good start to the winter snowpack in higher elevations.

Upper Lake Mary in Northern Arizona captures spring snowmelt and supplies up to 40% of Flagstaff's water. Since early October, the lake received more than 3 billion gallons of water. Brian Huntzinger, the water production manager for Flagstaff, said storms last weekend added the equivalent of more than two years of water to the town's surface supply. This provides a buffer for an operation that depends heavily on underground aquifers. Huntzinger suggested the town might overflow at this rate before snow arrives.

In central Arizona, heavy floodwaters trapped people in homes and gushed into streams feeding the Verde River. Bo Svoma, principal meteorologist at the Salt River Project, said water officials released water from two nearly full dams. They sent it into the Verde's normally dry stretch in metro Phoenix.

The region remains in drought despite the intense rains. Jack Schmidt, a professor at Utah State University who studies the Colorado River, said the U.S. Bureau of Reclamation is unlikely to change water releases from Lake Powell until snowpack peaks in April. Reclamation spokesperson Mary Carlson acknowledged that conditions have improved but said considerable uncertainty remains.

Under the federal plan for the Colorado River's Lower Basin, California, Nevada, and Arizona will collectively reduce water use by 1.25 million acre-feet annually in the next two years. That is enough to fill over 600,000 Olympic-sized swimming pools. Nevada and Arizona are challenging the plan in court. Some Arizona cities have agreed to fund preliminary work to expand an existing dam on the Verde River. The goal is to capture runoff from storms and reduce reliance on the Colorado River in a drier future.