Role of groundwater in watershed response and land surface feedbacks under climate change

We use an integrated, distributed groundwater-surface water-land surface model, ParFlow, to analyze integrated watershed response and groundwater-land surface feedbacks in the Little Washita River watershed, located within the southern Great Plains region of North America, under observed and perturbed climate conditions. Basin-scale hydrologic sensitivity to temperature and precipitation perturbations is shown to be greatest under energy-limited (direct runoff) conditions compared to moisture-limited (base flow) conditions. Feedbacks between groundwater depth and the land surface water and energy balance are shown to significantly influence surface fluxes under moisture-limited conditions, with differences in latent and sensible heat flux between areas of shallow and deep groundwater depth exceeding 75 W/m(2) under strongly energy-limited conditions. The influence of groundwater feedbacks on sensitivity of surface fluxes to changing climate conditions is shown to depend on changes in both moisture and energy availability over the watershed. Results demonstrate that hydrologic sensitivity to climate change depends on feedbacks between groundwater, overland flow, and the land surface water and energy balance. Results suggest not only that local and watershed response to global climate change depends on groundwater feedbacks but that the magnitude and seasonality of these feedbacks is sensitive to changes in climate.