An Assessment of Climate Change Impacts on Future Water Availability and Droughts in the Kentucky River Basin

Global climate change is expected to present a variety of challenges to water resources management. This study evaluated the potential impacts of climate change on hydrologic processes in the Kentucky River basin using the Soil and Water Assessment Tool (SWAT). Following calibration and validation, the SWAT model was forced with downscaled and bias-corrected forecasted precipitation and temperature outputs from a suite of eight CMIP5 GCMs, corresponding to two different representative concentration pathways (RCP 4.5 and 8.5) for two distinct time periods; 2036–2065 and 2070–2099, referred to as mid-century and late-century, respectively. Corrected climate projections indicate modest increases in average annual precipitation and with higher increases in temperature relative to the baseline (1976–2005) period. Modeled monthly water yield and surface runoff demonstrated increasing trends in spring and fall, while winter months are projected with decreasing trends. Evapotranspiration (ET) displayed a consistent increasing trend in winter and decreasing trend in summer under all future scenarios. Spatial analysis indicated basin-wide increases in water yield with the north-central portions likely to experience the smallest increase due to increases in ET. Meteorological and hydrological droughts were quantified using the Reconnaissance Drought Index (RDI) and Streamflow Drought Index (SDI). In general, maximum duration of hydrological drought is expected to increase, while drought intensity might decrease under future conditions. Meteorological droughts, however, are projected to be slightly less intense and of approximately the same duration as found for the baseline period. The overall findings suggest only modest changes in drought indices through the twenty-first century on a watershed basis, but that changes (and thus questions of future water reliability) might be more significant on the subwatershed basis.