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Analysis of the spatial and temporal variability of mountain snowpack and terrestrial water storage in the Upper Snake River, USA
Sproles, E., S. Leibowitz, J. Wigington, S. Patil, AND R. Comeleo. Analysis of the spatial and temporal variability of mountain snowpack and terrestrial water storage in the Upper Snake River, USA. Presented at Association of American Geographers, April 09 - 13, 2013.
The climate of the Pacific Northwestern (PNW) United States provides a surplus of water during the wet winter months. However during the dry summer months water supply is at its minimum while demand is at its maximum. Because the supply and demand of water in the PNW are seasonally misaligned, it is critical to understand water storage in the region. Much of the water available during the summer is winter surplus stored as terrestrial water and mountain snowpack. Snowmelt recharges terrestrial water and, despite its importance, a basin-scale approach to understanding inter-connections between snowmelt and terrestrial water does not exist for the PNW. To realize this goal, novel techniques that provide new measurements of water fluxes are needed. Geophysical monitoring can accomplish this at local scales, but are logistically unable to provide data at broad spatial scales. Data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellite provide measurements of the Earth’s water storage at the global scale. Analysis of GRACE data at the regional scale helps provide spatial and temporal estimates for terrestrial and snow water fluxes. This more nuanced understanding of the fluxes of water across the landscape can help identify scarcity with regards to time and space. In turn, this knowledge can help develop adaptive use and management strategies to deal with potential scarcity in present and projected climates The research described builds upon efforts in the Freshwater Ecology Branch of the EPA to develop and apply a hydrologic classification scheme for the PNW. The goal of this classification system is to provide a basic understanding of streamflow in each classification unit. However one of the limiting components is understanding the fluxes of water storage (terrestrial and snow). This research will aid in improving the classification system.
The spatial and temporal relationships of winter snowpack and terrestrial water storage (TWS) in the Upper Snake River were analyzed for water years 2001–2010 at a monthly time step. We coupled a regionally validated snow model with gravimetric measurements of the Earth’s water storage from NASA’s Gravity Recovery and Climate Experiment (GRACE) in this analytic and statistical assessment. An improved understanding of the connections between snow and TWS in this region is important since roughly 65-80% of annual precipitation falls as snow during the winter and early spring months. Here snow accumulates primarily in the mountains, and melts in the late spring and summer months. This melt is a key component of the hydrologic cycle because it recharges the valley aquifers that help sustain streamflows and provides water for irrigation during the drier summer months when the demand for water is high. The coupling of snow model and GRACE measurements provides a novel approach to understanding the spatial-temporal patterns and processes governing the movement of water from source areas (mountain snowpack) to sinks (valley aquifers). Initial results show distinct spatial patterns of intra-annual TWS variability moving from the local mountain ranges in the Upper Snake Basin to the valley floor, and suggest the influence of seasonal snow water storage. Comprehensive analysis will identify snowpack characteristics indicative of potential water scarcity in this watershed and augment a hydrologic classification framework for the region.