Late Season Water Supply Outlook Variable Across Colorado

Denver, CO – June 7th, 2024 – A cooler and wetter May have resulted in all but the Upper Rio Grande and the combined San Miguel-Dolores-Animas-San Juan River basins maintaining an above median snowpack. With much of the lower elevation snow melted out, only 45 of Colorado’s 124 SNOTEL stations recorded snow on the ground at the end of May. Most of the remaining snowpack is in northern and central basins along the Continental Divide. “During May, much of the central part of the state received above normal precipitation, combined with cooler temperatures, has allowed more snow to persist at higher elevations in some areas. These factors are leading to optimistic late season runoff volume forecasts for many river basins,” notes NRCS Hydrologist Joel Atwood. Runoff volume forecasts for June and July across the state are generally optimistic with the Gunnison, Arkansas and the combined Yampa-White-Little Snake River basins all forecasted to have well above median runoff. In addition, the South Platte and Colorado Headwaters River basins are also expecting slightly above median runoff volumes at 109 and 108 percent of median, respectively. Atwood continues, “In southern Colorado, many SNOTEL stations in the San Juan Mountains melted off around a week earlier than normal despite a near normal peak snowpack. In addition, the northern Sangre de Cristo mountains had a below normal peak snowpack. These conditions contribute to a less optimistic late season water supply in southwest Colorado.” The southwestern river basins of the combined San Miguel-Dolores-Animas-San Juan and Upper Rio Grande are forecasted to have below normal runoff volumes for June and July, at 59 and 74 percent of median, respectively. 

At of the end of May, reservoir storage across Colorado was 94 percent of median. Several basins were reporting above median storage, ranging from 100 percent of median in the Arkansas River basin to 112 percent of median in the Colorado Headwaters River basin. The combined San Miguel-Dolores-Animas-San Juan, Upper Rio Grande and Eastern Arkansas River basins all were reporting below median reservoir storage ranging from 70 percent of median in the Eastern Arkansas River basin to 86 percent of median in the Gunnison River basin.

Most of the state received well above median precipitation with a few exceptions. The combined Laramie-North Platte, South Platte, and San Miguel-Dolores-Animas-San Juan River basins each received 100, 89 and 63 percent of median precipitation, respectively. Other basin across the state received much higher totals compared to normal, ranging from 110 percent of median in the Colorado Headwaters River basin to 153 percent of median in the Arkansas River basin. Statewide precipitation during May was above normal at 107 percent of median.

_{* San Miguel-Dolores-Animas-San Juan River basin}

_{* *For more detailed information about April mountain snowpack refer to the June 1st, 2024 Colorado Water Supply Outlook Report. For the most up to date information about Colorado snowpack and water supply related information, refer to the Colorado Snow Survey website.}