Drought conditions may return to western Colorado #COdrought

From the Glenwood Springs Post Independent (Hannah Holm):

As of Dec. 30, the Natural Resource Conservation Service reported that snowpack in the Colorado River Basin in Colorado was at 102 percent of the median for this date, while the Gunnison Basin was at 108 percent, as were the Yampa and White Basins, and the state’s southwestern river basins were at 102 percent. This is down from a few weeks ago, but it’s still looking pretty good.

All in all, the water situation is feeling more comfortable than it has for a couple of years. Zooming out in time and space, though, provides a less comforting picture.

According to the U.S. Drought Monitor, most of the Colorado River Basin remains either “abnormally dry” or in “moderate” to “severe” drought. Most of western Colorado is still in the abnormally dry category, while drought lingers in northwestern New Mexico and northeastern Arizona. Areas outside of the basin that depend on transfusions of Colorado River water, including much of southern California, are also still in drought.

Looking ahead three months, the U.S. Drought Monitor forecasts warmer and drier conditions across much of the Southwest. This could bring back drought conditions here and cause them to persist elsewhere in the Colorado River Basin.

We depend on reservoir storage to minimize disruptions to water use during droughts. They have been doing their job well over the past 10 years, as water demands in the Colorado River Basin have exceeded inflows from rain and snow. Reservoirs take longer to recover than soils and streams, however, once drought conditions ease.

Currently, most of the region’s big reservoirs are fairly depleted. Lake Powell, the biggest bucket in the Upper Colorado Basin, is only 43 percent full, and Blue Mesa Reservoir, the biggest bucket in Colorado, is 45 percent full. Navajo Reservoir in northwestern New Mexico is 57 percent full, and Flaming Gorge, on the Wyoming/Utah border, is better off at 75 percent full. To put that in seasonal perspective, Lake Powell is at 55 percent of average for this time of year, Blue Mesa is at 68 percent of average, Navajo and Flaming Gorge are at about 75 percent of average.

In Colorado, Lake Dillon is the only big reservoir with a level that’s above average for this time of year. It’s 95 percent full, which is 109 percent of average for this time of year. Green Mountain Reservoir, an important safety net for much of western Colorado, is 56 percent full, which is 95 percent of average for this time of year.

A return to drought in western Colorado and continued drought across other parts of the Colorado River Basin could have wide-ranging effects, from environmental stress to reduced water available for irrigation. Power generation could be another casualty. Lake Powell releases to the Lower Basin are already set to be reduced for the first time since Powell filled, and if Powell’s levels drop much more, it won’t be able to continue producing electricity through its turbines.

One more year of drought is unlikely to cause a major catastrophe. A longer-term continuation, however, which tree ring studies show has occurred in the past, could require major adjustments to how we rely on and manage our rivers.

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