Basin-Scale Water Resources Assessment in Oklahoma under Synthetic Climate Change Scenarios Using a Fully Distributed Hydrologic Model

Climate change resulting from the enhanced greenhouse effect is expected to have significant implications for the hydrological cycle. Several studies have pointed out the importance of basin-scale investigations for determining regional impacts on water resources, including the effects of floods and droughts. In this study, a fully distributed hydrologic model is used to assess the potential impacts of climate change on water availability in a basin in Oklahoma (United States). With this aim, the hydrologic model was applied for current conditions as well as under the hypotheses of climate variations represented by scenarios consistent with a climatic trend analysis generated using a stochastic weather model. Hydrologic simulations indicate that streamflow and evapotranspiration reflect variations in precipitation differently. Positive trends in precipitation result in an increase in surface and groundwater resources, while evapotranspiration is only affected slightly due to the higher soil moisture in the basin. Sensitivity analyses of the evapotranspiration and runoff changes to precipitation variations confirm these results. Comparisons of the impacts of the precipitation trend on surface and groundwater resources showed that the increase of surface water resources is similar to 3 times greater, implying the groundwater system is affected less by climate change. The use of a distributed model also provided insight on the spatial variation of the water balance components. Results showed that the most significant increases of soil moisture (similar to 60%) are located along the river network and in the flat areas of the basin, characterized by a higher frequency of saturation excess runoff. In summary, climate change scenarios in this region produced an increase in water resources that can have beneficial impacts, but these positive effects are tempered by the increasing potential for flood risk. The increase of this risk has been evaluated as well in this analysis.