Assessment of Climate Change Impact on Watershed Hydrology

Abstract

Evidence of pronounced fluctuation in climate variability has caused numerous impact assessment studies of climate variability and change on watershed hydrology. Several methods of impact assessment have been used over the last decade which basically incorporates atmospheric-ocean circulation-based climate models’ projection of changes in meteorological variable into the simulation of land surface hydrological processes. In this study, we have evaluated two methods, frequency perturbation and direct use of data, through forcing of a simulation model with data from a suite of global climate models. Hydrologic response of a typical watershed in Midwest was evaluated for the change in climatic condition. Frequency perturbation method found precipitation decrease by 17 % and reduction in temperature by 0.43 °C on an average annual basis. The changes when applied through the watershed simulation model resulted in 13 % reduction in evapotranspiration (ET) and 25 % reduction in water yield. In contrast, direct method with 1.25 % decrease in precipitation and 0.2 °C decrease in temperature on annual basin found an increase of 1.8 % for ET and 5 % reduction in water yield. Changes in ET and water yield on temporal and spatial scale due to changes in future climate are likely to have severe implications for the water availability. However, more research is needed to evaluate several impact assessment methods for more accurate analysis.