Ground Water and Climate Change: Interactions, Feedbacks, and Effects of Modified Atmospheric Forcing on Hydrologic Response

  Recent studies have demonstrated that groundwater depth influences land surface processes, including land-atmosphere fluxes of latent and sensible heat.  Through its effects on surface water and energy budgets, groundwater depth is a key determinant of susceptibility to changes in temperature and precipitation, and is critical to understanding processes of recharge and drought in a changing climate.  Here we use a variably saturated groundwater flow model with integrated land-surface and overland flow processes to examine changes in groundwater-land surface interactions for the southern Great Plains, USA.  Using a suite of scenario simulations with modified temperature and precipitation forcings, we analyze the ‘critical zone’ of strong groundwater-land surface coupling under changing climate conditions.  Changes in the spatial extent, depth, and coupling strength of the critical zone are presented for each season, focusing on tipping points between temperature controlled, groundwater controlled, and precipitation controlled regimes of the surface energy and water balances.  In addition, we analyze streamflow characteristics; changes in seasonal streamflow are presented, focusing on changes in runoff and baseflow characteristics.  Implications are discussed in the context of climate variability, climate change, and water resources management.