The Dolores River Basin is a snowmelt-dominated basin located in the southwest corner of Colorado’s iconic San Juan mountains. Runoff into the Dolores River system sustains a large amount of irrigated agriculture, gold medal trout fisheries, and a growing river boating recreational community. These industries provide critical revenue into local economies. Dolores River water also is an important contributor to downstream flows into the Uncompahgre and then Colorado Rivers thereby playing an important role in the overall reliability of Colorado River flows. As one of the most southerly basins in Colorado, the Dolores River basin is increasingly influenced by warming trends associated with global climate change and has already seen decreases in the seasonal duration of snow cover as well as prolonged periods of low flow conditions.

From a water management perspective, the primary control on the Dolores River resides at McPhee Reservoir which stores and releases water to the lower Dolores River basin. The Dolores Water Conservancy District (DWCD) manages McPhee Reservoir and has been a regular user of ASO data since 2021. The DWCD must carefully balance the competing uses on the Dolores River (irrigation, fish health, recreational releases) with the goal to ultimately refill the reservoir prior to each year’s irrigation season. Operation of the reservoir is highly influenced by snowpack observations and runoff forecasting from the upper Dolores River basin. As a southerly basin, it is typically one of the first basins in the Upper Colorado River Basin to initiate seasonal runoff as early as early-to-mid-March in some years implying that typical April 1 metrics of snowpack are potentially, and will increasingly be, inadequate to predict total seasonal runoff. Runoff from the summer monsoon season typically adds a significant, but small fraction of additional flow into the Dolores River system. Therefore, there is a premium on the availability and accuracy of snowpack information towards the end of winter and the ability of models to accurately predict the timing and amount of seasonal flows.