Drier Soils In A Warming World? Examining The Relationship Between Soil-Water Stress And Snow Persistence In The Mountain West
Stamper, Brooke E 1 ; Harpold, Adrian 2 ; Molotch, Noah 3
1 University of Colorado
2 University of Colorado
3 University of Colorado
The Western U.S. is heavily reliant on snowmelt for water used by humans and ecosystem services. Regional warming is expected to reduce snowpacks and cause faster and earlier snowmelts. The ecological and hydrological consequences of these changes to snowmelt are not well understood due to the large variability in soil properties, snowmelt timing, and post-snowmelt rainfall. In this study we employ a dataset utilizing stations where co-existing measurements of snowpack, precipitation, soil moisture, and soil properties exist to ask: “When and where do smaller and/or earlier snowmelts lead to increased soil water stress?” Precipitation and soil moisture information was gathered from 48 stations that were part of Natural Resources Conservation Center (NRCS) snow telemetry (SNOTEL) and the Soil Climate Analysis Network (SCAN). In addition, the National Cooperative Soil Survey (NCSS) was used to estimate soil properties at multiple soil horizons. In order to quantify soil-water stress in the top 20 cm, the number of growing-season days below wilting point was analyzed at soil horizons of 5cm, 10cm, and 20cm depth. Precipitation was summed for the winter and post-snowmelt season as well as, maximum annual snow water equivalent, and day of snow disappearance. Focusing in the Northwest U.S., preliminary results found that the timing of snow disappearance was a stronger predictor of the duration of water stress (defined as soil moisture below wilting point) than annual or seasonal precipitation. Surprisingly, we see little direct control of post-snowmelt rainfall on reducing growing-season water stress. This does not bode well for continued changes to earlier snowmelt and larger more intense summer rainfall in much of the Western U.S. It is important to understand soil water availability under a warming climate in order to manage and mitigate the impacts on water resources for both humans and ecosystems.