Denver, CO – May 5th, 2022 – Varying weather patterns over the month of April, as well as other factors including dust-on-snow, have driven dramatically different snowmelt patterns across Colorado as we progress further into snowmelt runoff season. The Gunnison, Rio Grande, Arkansas, and combined San Miguel, Dolores, Animas, and San Juan basins all received less than 60 percent of normal April precipitation. All basins to the north accumulated between 76 and 114 percent. Lack of new snow accumulation in combination with significant amounts of dust on the snow surface (which retains more energy from the sun) has greatly accelerated loss of snowpack in southern Colorado. NRCS Hydrologist Karl Wetlaufer goes further “As an example, the Rio Grande basin achieved near normal peak snowpack accumulation and timing but there is now less than 20 percent of that snow left at SNOTEL sites. In contrast, the North Platte and South Platte basins have lost very minimal net snowpack since the initial signs of melt during the third week of April.”
There are currently very few individual streamflow forecast points in the state calling for above normal runoff volumes for the May through July period. The average of forecasts in the combined San Miguel, Dolores, Animas, and San Juan basins is the lowest in the state at 59 percent of normal followed by the Rio Grande at 60 percent. The average of forecasts in the Colorado, Gunnison, Arkansas, and South Platte basins are all near 80 percent of normal. The Yampa and North Platte have the highest May through July forecasts at 90 and 101 percent of normal, respectively.
In addition to snowpack and streamflow forecasts the importance of reservoir storage to water supply in Colorado and to downstream states is no exception this year. Reservoir storage in the major basins of the Western Slope are all below 90 percent of normal values while all others are holding above 90 percent. The Gunnison basin has the lowest storage in the state and provides an important reminder of the connectedness of water resources in a headwaters state such as Colorado. With Lake Powell and Lake Mead at historic low levels management plans across the Colorado River basin have been geared towards maintaining hydropower production at Lake Powell. This has contributed to leaving Blue Mesa Reservoir at some of the lowest levels since it first filled in the 1960s. Wetlaufer summarizes that “This year’s water supply will need to be monitored closely and looked at basin-by-basin for the remainder of the water year. With low streamflow forecasts in combination with low reservoir storage Western, and particularly Southwest Colorado, have a difficult water supply management situation this year.”
|Basin||% Median Snowpack||Last Year’s % median Snowpack||% Median Reservoir Storage||Last Year’s % Median Res. Storage|
|Upper Rio Grande||42||75||92||87|
* San Miguel-Dolores-Animas-San Juan River basin
For more details see the May 1st Water Supply Outlook Report.