The health of our waters is the principal measure of how we live on the land — Luna Leopold
Generous May Precipitation Ends #Snowpack Season — NRCS
Here’s the release from the NRCS (Brian Domonkos):
Precipitation during the month of May has failed to disappoint in recent years. While Colorado’s mountains did not receive the same amounts seen during May of 2015, May 2017 totaled 135 percent of normal precipitation after a lackluster combined March and April. This May also brought more precipitation than last year and in 2014. As a result, water year-to-date precipitation trended upward from 108 percent of average last month to 111 percent of average this month.
About 25 percent of this year’s snowpack remains and is currently melting out slightly later than normal. Brian Domonkos, from the U.S. Department of Agriculture’s Colorado Snow Survey Program, adds “For Colorado it is normal to see snow fall at all elevations during the month of May, however sun and warm temperatures often follow 24 to 48 hours later.” Sun and warm temperatures often prevail in May melting the snowpack and causing streams to rise.
Statewide snowpack time series June 5, 2017 via the NRCS.
Looking more broadly across the western U.S., Domonkos highlights, “Colorado and more particularly the Front Range and Sangre de Cristo Mountains were the epicenter of heavy mountain precipitation during May, relative to normal amounts.” Some SNOTEL sites reported 200 percent of normal or more monthly precipitation. The South Platte River basin was the largest benefactor of a mid-May storm that dropped snow at most elevations and delivered precipitation to much of Colorado. After a turbulent winter, May provided a boost to water supplies, reassuring water managers that this year’s snowpack could provide ample water supplies entering the summer months.
Reservoir operators have continued to maintain encouraging storage levels across most areas, such as the South Platte and Arkansas watersheds, which are at 112 percent and 119 percent of average respectively. Statewide, reservoirs decreased slightly from 113 percent to 109 percent of average over the last month, due in large part to planned spring peak outflows of the Aspinall Unit on the Gunnison River. Despite these simulated seasonal flows, combined reservoir levels in the Gunnison River basin remain above normal at 103 percent of average.
Although there are extremes of both high and low volumes, most water supply forecasts are within 20 percent of normal for future runoff volumes. Current forecasts range from 167% of average on the Los Pinos River near Ortiz to 58% of average on Elkhead Creek above Long Gulch. For more specific forecast values and water supply prospects view the Colorado Water Supply Outlook Report.
