Changes in Climate and Its Effect on Timing of Snowmelt and Intensity-Duration-Frequency Curves
Dr. Anna Wagner | Cold Regions Research and Engineering Laboratory
Snow accumulation and ablation characteristics are changing in most watersheds where snow accounts for more than 50% of the annual precipitation. Although snow cover extent is generally decreasing globally, changes in local and regional snowmelt timing can result in faster snowmelt rates and lead to flooding. Failure to account for these climate changes could result in deleterious military asset impacts. To advance the Department of Defense’s (DoD) ability to manage and adapt to winter and spring runoff events, this project will develop an improved understanding of snow accumulation and runoff timing, intensity, duration, and long-term trends as affected by a changing climate. The objectives are to: (1) investigate the timing of and intensity of snow accumulation, snowmelt, and runoff for historical and future climate scenarios at regional and watershed scales and (2) produce current and future intensity-duration-frequency (IDF) runoff curves for the study locations.
The technical approach includes five tasks. Task 1 will produce spatially explicit historic (1940 to 2014) and future (2010 to 2080) snow depth, duration, and snowmelt events by performing snow accumulation on a regional scale (western contiguous United States) and at a local higher resolution scale for the Joint Base Lewis McChord Yakima Training Center (hereafter referred to as Yakima), WA; Fort Carson, CO; and Grand Forks Air Force Base, ND. This task also includes performing snow surveys at local study sites. In Task 2 runoff modeling will be performed for the areas described in Task 1. In Task 3 the snow model results will be incorporated into the hydrological model and model outputs will be verified with field measurements, satellite imagery, and existing stream gauge data. For Task 4 statistical analyses will be conducted to determine changes in the timing of snowmelt and streamflow at regional and local scales. IDF runoff curves will be generated for selected locations to assess the importance and frequency of extreme events. This task will synthesize our understanding of climate change and its impacts on IDF runoff curves for the study areas. Particular attention will be paid to the non-stationary relationships among snowmelt, rainfall, and runoff in watersheds with three distinct and variable snow regimes experiencing change. Finally, Task 5 includes summarizing the results in a cross-project Best Practices Manual.
The primary benefit to DoD of this research is a spatially-explicit 75-year snow and runoff climatology and a 90-year forecast of snow conditions needed to identify management vulnerabilities and inform infrastructure planning. New IDF runoff curves produced as part of this work will benefit the DoD by defining the impacts and thus allowing for development of mitigation or adaptation strategies, leading to lower operational costs. The results will improve the current knowledge of climate change effect on snowmelt, runoff, and hydrology. The scientific community also will benefit from an integrated approach that includes measurement, improved modeling, and future climate projections. The field and modeling methods will be transferable to myriad locations where snowmelt and its subsequent runoff present a challenge to infrastructure planning and maintenance. (Anticipated Project Completion - 2019)