Hydroclimate and Streamflow in the San Juan Mountains, Colorado

Authors: Chris Hancock*, Northern Arizona University
Topics: Climatology and Meteorology, Mountain Environments, Water Resources and Hydrology
Keywords: Hydroclimate, Climate Change, Alpine, SWE, Climate, Streamflow, Colorado
Session Type: Virtual Paper
Day: 4/10/2021
Start / End Time: 4:40 PM / 5:55 PM
Room: Virtual 46
Presentation File: No File Uploaded

An examination into to the annual snowpack and snowmelt hydrology of the San Juan Mountains provides insight into the changing hydroclimatic patterns of alpine regions across the Southern Rocky Mountains. This research is vital for understanding how climate change will impact water resources through shifting precipitation, snowpack, and streamflow patterns. Datasets analyzed for this study include 79 SNOTEL sites throughout Colorado (24 in the San Juan Mountains), which provide climate metrics for Water Years 1988-2018, and impacts on streamflow were evaluated in the San Juan Region through a subset of 11 USGS stream gauges. Results indicate that flood frequency values match snowmelt dominated regions across the Rocky Mountains. Strong correlations between annual discharge values and SWE totals further support this relationship, and variability between watersheds primarily reflects elevation constraints on the snow accumulation processes. While precipitation regulates the quantity of streamflow to a greater degree than the larger-scale Upper Colorado River Basin, temperature plays a strong role in the timing of the snowmelt runoff period. Over the 31-year study period, SNOTEL sites have recorded a 1.05℃/decade warming trend with significant shifts towards earlier snowmelt discharge (-3.7 days/decade). In addition, the relative rate of warming has increased over the most recent 2007-2018 period with a corresponding SWEMaxDate reduction of -5 days/decade. SWEMax values have also decreased by 2.5 cm/decade, but these changes are offset by increases in late season snow accumulation events. Thus, observed SWEMax reductions are largely a product of earlier temperature induced snowmelt rather than lower total snowpack (SWETotal).

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