AQUIFER RECHARGE AND WATERSHED RESPONSE TO CLIMATE CHANGE IN THE UPPER UMATILLA RIVER SUBBASIN USING THE PRECIPITATION RUNOFF MODELING SYSTEM

Abstract:

Groundwater recharge in the Columbia River Basalt Group (CRBG) in the Umatilla River Basin, OR, is poorly understood. The long-term decline of groundwater storage in the basalt aquifers, present a serious environmental challenge for the Confederated Tribes of the Umatilla Indian Reservation (CTUIR). This study will provide a groundwater estimate to help CTUIR better understand the hydrologic budget and inform water management decisions for present and future needs. The study site is in the upper Umatilla River Subbasin in Northeastern Oregon with an area that is 2,365 km². The Precipitation Runoff Modeling System (PRMS) developed by the U.S. Geological Survey (USGS) is a distributed-parameter, physical-process watershed model that will be used to calculate groundwater recharge and simulate the watershed response to different climate and land use scenarios (Markstrom, 2008). The response of the hydrologic regime to climate change in the 2050s and 2080s will be determined using three downscaled Global Climate Models (GCMs), including the Earth System model of the Hadley Centre Global Environment Model, Version 2 (HadGEM2-ES), Model for Interdisciplinary Research on Climate (MIROC5), and the Geophysical Fluid Dynamics Laboratory - Earth System Model, (GFDL-ESM2M). The relationships between hydrologic processes at the surface, soil-zone, subsurface and groundwater reservoirs will be studied and defined in a water budget analysis to characterize the hydrologic regime in response to climate change.