ASSESSING CLIMATE CHANGE EFFECTS ON SURFACE WATER RESOURCES IN THE LOWER BASIN WATERSHED OF THE COLORADO RIVER

A common approach that is widely used by the scientific community to generate future climate projections at required spatial and temporal resolutions is the use of different downscaling techniques. The objective of this study was to assess the effects of potential cliamte change scenarios on streameflow in the Lower Basin Watershed, one of the Colorado River Basin Watersheds in Texas. Long-term daily climate data (rainfall, minimum and maximum temperatures) was obtained from the Lower Colorado River Authority (LCRA) and the Climate Forecast System Reanalysis (CFSR) for the period 1981-2010. The Long Ashton Research Station-Weather Generator (LARS-WG) statistical model was used to downscale outputs from 15 General Circulation Models (GCMs) for two future periods: 2055s (2046-2065) and 2090s (2080-2099) under two greenhouse gas emission (A2 [high emission] and B1 [low emission]) scenarios. In addition, a calibrated and validated Soil and Water Assessment Tool (SWAT) hydrologic model, which is commonly used to simulate streamflow at watershed and basin scales, was used to simulate streamflow using downscaled data from the 15 GCMs. Overall, results show that streamflow will greatly vary both spatially and temporally. While all GCMs agreed in their predictions of minimum and maximum temperature, GCMs predictions of precipitation showed greater variability and contradictoriction at times. Overall predictions based on multi-model ensemble projections show that annual streamflow will decrease considerably towards the end of the 21^st century.