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As of May 1st, 2024, Colorado’s snowpack exhibits a distinct north-south divide and is at 90% of median. The northern basins display persistent snowpack levels from 95% of median in the combined Yampa-White-Little Snake basins to 105% in the South Platte. In stark contrast, the southern basins are below median ranging from 57% in the Upper Rio Grande to 84% in the Arkansas. Statewide precipitation has reached 105% of median for the water year to date (WYTD), while April’s drier conditions have resulted in 88% of median precipitation. This monthly subnormal statewide median, when disaggregated, reveals a stark contrast in precipitation distribution, particularly with southern basins ranging from 54% to 68% and northern basins ranging from 82% to 102%. Southern basins have not only received less precipitation compared to the state’s median but also when set against their historical medians. The combined San Miguel-Dolores-Animas-San Juan (SMDASJ) basins are at 88% WYTD, dipping further to 68% for April totals.
Streamflow projections echo snowpack and precipitation variances, with the state averaging forecasts at 95% of median. A closer look reveals 34 of 86 streamflow stations predicting above median flows. The Yampa-White-Little Snake forecast an above median flow at 109%, reflecting sustained snowpack levels. Conversely, the combined SMDASJ basins, experiencing reduced snowpack at 72%, project streamflow at 73% of median. Specific sites like Navajo Reservoir inflow and the Animas River at Durango are anticipating below median streamflow at 440 cubic feet per second (CFS) and 279 CFS, respectively.
Karl Wetlaufer, a hydrologist with the NRCS Water and Climate Center, highlights the impact of recent weather patterns on streamflow projections: “The month of April brought above normal temperatures and below normal precipitation across the Upper Colorado and the Rio Grande basins. These conditions contributed to rapid snowmelt in most of the basins and above normal monthly streamflow in many sub-basins. All of these contributing factors led to a drop in total seasonal (April-July) volumetric forecasts since April 1st in most sub-basins with the exception of the Colorado Headwaters where forecasts remained most similar to last month.”
“The rapid onset of warmer temperatures in late April accelerated snowmelt rates, particularly in the Upper Colorado and Gunnison basins, highlights a potential for early peak streamflow,” comments Nagam Gill, NRCS hydrologist. SNOTEL data at the Schofield Pass and Red Mountain Pass sites in the Gunnison basin, show that snow water equivalent (SWE) was reduced to 75% and 90% of the seasonal peak, respectively, by early May. This trend is also observed at the Upper Taylor SNOTEL, where the snow water equivalent decreased to 48% of its peak by the same time, earlier than the historical median melt-out dates. Despite the past peak in SWE, ongoing weather patterns into May and June can still influence streamflow. Late spring rains, although not as impactful as winter snowpack, can help sustain streamflow and top up reservoirs levels before the drier summer months set in.
As of the end of April, reservoir storage across Colorado is at 97% of median an improvement from 86% observed this time last year. Most basins are reporting near to above median, ranging from 106% in the South Platte to 124% in the Colorado Headwaters. The combined SMDASJ basins are the exception at 84% of median slightly above last year’s 82% at this time. Despite less robust snowpack conditions this year, reservoir levels have benefited from last year’s abundant snowpack, which has helped maintain relatively high-water storage levels.
* San Miguel-Dolores-Animas-San Juan River basin
* *For more detailed information about April mountain snowpack refer to the May1st, 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.