Water Yield Responses to High and Low Spatial Resolution Climate Change Scenarios in the Missouri River Basinby Mark Stone,
Abstract: Water yield responses to two climate change scenarios of different spatial scales were compared. Responses were determined by applying the Soil and Water Assessment Tool (SWAT) hydrologic model to the Missouri River Basin using data from the climate change scenarios. Although, several techniques have been developed for generating high resolution climate change scenarios, few studies have investigated whether higher resolution scenarios result in important differences in the calculations of climate change impacts. The Commonwealth Scientific and Industrial Research Organization (CSIRO) Global Circulation Model (GCM) was used for this study. The CSIRO GCM simulated control and doubled CO2 climate scenarios. Climate data was produced at a spatial resolution equivalent to 3.2 degrees latitude (400 km) by 5.6 degrees longitude (500 km). The high resolution climate change scenario was developed using the National Center for Atmospheric Research (NCAR) Regional Climate Model (RegCM). The NCAR method used a nested regional modeling technique whereby the RegCM was nested within the control and doubled CO2 runs of the CSIRO GCM. The RegCM was run at a spatial resolution of 50 km. SWAT was chosen as the hydrologic model on the strength of prior applications. SWAT is a distributed, daily time step hydrologic model capable of simulating the impacts of increased carbon dioxide on plant growth efficiency. The model was modified to simulate the complex operation of the main stem dams on the Missouri River. The model was also modified to incorporate the daily climatic inputs from climate change models and to improve snowmelt simulation. SWAT simulation results exhibit dramatic increases in water yields of more than 200% across the central and northern portions of the Missouri River basin and decreases of 50% or more in the southeast and northwest regions. Overall, water yields increased by approximately 100% for the basin. Water yield responses to the high and low resolution climate change scenarios were investigated at time spans of 5 years, 1 year, and 1 month. No water yield changes were found for the 5-year time span. Only minor changes were found for the 1-year and 1-month time spans. A sensitivity analysis using stochastically generated climate data in place of historic data showed that SWAT was sensitive to small changes in climate. Therefore, the minor water yield changes between the GCM and RegCM simulations were not significant.
Subject Headings: Climate change | Hydrologic models | Water yield | Basins | Rivers and streams | Weather forecasting | Simulation models | Missouri River
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