An Early Start to Runoff and Reduced Seasonal Volume

Denver, CO - April 9, 2026 - In a typical year, early April marks the transition into peak snowpack. Accumulation is still ongoing, particularly across the central and northern mountains, and runoff has yet to fully begin. This year, that sequence has shifted. Snowpack peak snow water equivalent(SWE) timing occurred early, with many basins reaching maximum SWE in late-February to mid-March. In the San Juan Mountains, peak SWE was largely driven by a late February storm, after which snowpack shifted into net melt through March rather than functioning as a late-season accumulation period.

As of April 9, 2026, statewide SWE is 22 percent of median, following a brief increase to 26 percent after early April storms. While beneficial at the site level, these storms did not change conditions and sites have resumed melt-out patterns.

Statewide SWE declined from 60 percent of median from March 1, 2026 to 20 percent of median by April 1, 2026. The most rapid decline occurred during a concentrated melt period from mid to late March, when sustained record temperatures drove accelerated depletion across the network. During this interval, SWE declined at an average rate of 0.25 inches per day. March temperature dataaveraged roughly 9°F above normal, with 26 days exceeding median. Rather than intermittent melt cycles, snowpack experienced sustained energy input, accelerating SWE lossacross elevations, including high-elevation zones that typically remain stable into April.

Across the Colorado monitoring network, snowpack is clustered at the lower end of the observing SNOTEL period. As of the end March, 103 of 117 sites are reporting values at or near the 0^th percentile with 95 percent of sites at the lowest or second lowest values. This pattern extends beyond Colorado, with SNOTEL sites across the Intermountain West averaging near the 12^th percentile at the end of March.

March streamflow observationsare above median across much of Colorado. Outside of the eastern Sangre de Cristo Mountains, where flows are closer to 58 percent of median, many basins are averaging 140 percent above median. Under normal conditions, above median runoff would indicate strong water supply. This reflects a shift in timing and a reduction in total volume. Snowmelt that would typically contribute to April through July runoff (primary period) is now entering into river systems. Several headwater locations are approaching or have reached seasonal peak streamflow flow timingweeks earlier than average. Early flows may appear favorable in the short term, but in this case may represent a compression of the runoff period rather than an increase in total seasonal supply.

At the 50 percent outlook, primary period runoff is expected to fall 11.4 million acre-feet (MAF) below median runoff volume statewide, with 9.4 MAF of that deficit concentrated in western slope basins, including the Colorado Headwaters, Gunnison, Yampa-White-Litte Snake and San Miguel-Dolores-Animas-San Juan (SMDASJ) basins. The 30 percent forecast remains well below median, while the 70 and 90 percent forecasts reduce volumes further, with Colorado Headwaters ranging from 3.5 to 4.8 MAF below median across the outlook range.

Figure 1. Primary period streamflow forecast at the 70 percent exceedance probability (NRCS 1991-2020 median). Basin-scale runoff departures exceed 4 MAF below median in the Colorado Headwaters and more than 2 MAF in the Gunnison. 56 of 80 points fall at or near the lowest values.

April-July runoff forecasts at the 50 percent exceedance probability are in the range of 27-35 percent of median depending on basin, with continued degradations from prior outlooks. The South Platte basin is higher relative to other basins, with a forecast at 54 percent of median. At the 70 percent exceedance streamflow forecastand 90 percent exceedance streamflow forecast,a majority of points fall near the lowest values in their period of record. Figure 1 highlights the lower range of outcomes. Many of these gauges have observing periods exceeding 100 years, placing drier projections at the bottom in the historical record.

October brought above-normal precipitation, particularly in southern basins where a significant portion fell as rain and contributed directly to runoff and reservoir storage. Since then, precipitation has remained well below normal across the state and has limited snowpack development during the primary accumulation window. Statewide reservoir storage is near average at 89 percent of median. A portion of this year's runoff has already occurred during March, and the snowpack entering April is substantially below normal. These conditions limit the volume available for the rest of the runoff period, consistent with projected runoff volumes well below median. Short-term forecasts indicate above average precipitation, which may provide temporary increases in snowpack. Conversely, seasonal Climate Predication Center outlooks favor above-normal temperatures and below-normal precipitation. Forecasts remain centered below median and are trending toward the lower exceedance range.

Colorado's Snowpack and Reservoir Storage as of April 1, 2026

* San Miguel-Dolores-Animas-San Juan River basin

* *For more detailed information about mountain snowpack refer to the 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.