Below-normal #snowpack increases #drought conditions — The Mountain Mail #runoff

West Drought Monitor map May 4, 2021.

From The Mountain Mail (Brian McCabe):

Drought conditions in April increased in much of western Colorado, as already dry conditions were made worse by well-below-average precipitation, the Colorado Water Supply Outlook stated in its May report.

Higher temperatures in the high country worsened the situation with substantial loss of snowpack, which fell to 72 percent of median statewide by the end of April…

Statewide, 33 SNOTEL sites saw the lowest precipitation on record, while 15 other sites recorded the second-lowest precipitation on record for April. Most of those SNOTEL sites were west of the Continental Divide.

Dry conditions will impact water storage for the coming summer months. Reservoir storage in all river basins, except the South Platte and Arkansas, saw a decrease in relative storage. Statewide reservoir storage is 84 percent of normal, a percentage point drop from April.

An above-average warm and dry April caused a decline in forecasted water supplies. All basins west of the Continental Divide are now forecast to have streamflow volumes below 60 percent of average. East of the divide, conditions are a little better, with forecasts for the South Platte and Arkansas river basins anticipating streamflow volumes at 88 and 71 percent of average, respectively.

Streamflow forecasts for much of Colorado are discouraging, with most of the rivers seeing volumes well below normal.

West of the Continental Divide, runoff conditions are deteriorating. In western Colorado, below-average precipitation and higher temperatures have reduced snowpack. Forty-one of the streamflow forecast points are predicted to have a top-10 lowest runoff volume on record.

The Gunnison Basin, the Yampa-white-Little Snake River Basin and the San Miguel-Dolores-Animas-San Juan River Basin are all projected to be below 50 percent of average streamflow volumes.

Snowpack in the Arkansas River Basin is below normal at 76 percent of median. Precipitation for April was 41 percent of average, which brings the water year-to-date precipitation to 83 percent of average.

Reservoir storage at the end of April was 69 percent of average, compared to 91 percent in April 2020.

Current streamflow forecasts range from 81 percent of average on the Cucharas River near La Veta to 64 percent of average on Chalk Creek near Nathrop for May to July.

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