Impacts of Climate Change on Regional Hydrological Regimes in the Spokane River Watershed

Abstract

This study develops and implements a methodology to estimate the impacts of global climate change on regional hydrological regimes using ArcGIS Geostatistical Analyst. The model is easily used and can be expanded to different watersheds. The ArcGIS Geostatistical Analyst interface provides a comprehensive set of tools for creating surfaces from measured sample points compared with the previous method of using adjustable tension continuous curvature surface gridding. As a result, users can rapidly compare different interpolation techniques in order to obtain the best solution. Model results can subsequently be used in GIS models for visualization and analyses. The methodology was applied to the Spokane River Watershed. Results indicate that a 30% precipitation increase causes a 50% increase of streamflow when the temperature is normal compared to only a 20-30% increase in streamflow if the average annual air temperature is 1.5°C higher than normal. Conversely, a 20% precipitation decrease results in approximately 25-30% less streamflow when the temperature is normal but a 45% decrease in streamflow if the temperature is 1.5°C higher than normal. These research results can be used as reference conditions for long-term watershed water management strategies under global warming scenarios. The precipitation elasticity of runoff is also investigated. The precipitation elasticity was found to be 1.67 although it varied with precipitation and temperature. © 2007 ASCE.