Enhancing the link between surface and groundwater models for climate change assessment of water supply and demand in Northwest Mexico

The integrated use of surface and groundwater models is critical for analyzing water resources sustainability. We have applied surface and groundwater models to the Sonora River basin (SRB) in Northwest Mexico within the context of participatory modeling with stakeholders to explore alternative futures under climate change impacts. The models are used to assess the hydrologic consequences of temperature and precipitation scenarios generated through the dynamical downscaling using the Weather Research and Forecast (WRF) model for historical, near-future and far-future study periods. WRF is used to downscale two global circulation models (GCMs), HadCM3 and MPI-ECHAM5. Improved representation of surface-groundwater interactions is achieved through a calibration exercise with respect to two stream gauging stations using an automated parameter optimization algorithm. Results from the surface water model depend on the GCM, with the HadCM3 producing higher precipitation and streamflows, but comparable evapotranspiration in the future climate change scenarios as compared to the historical simulations. The MPI-ECHAM5 produces much higher rainfall and streamflows during the historical period than the HadCM3, but followed by decreases in rainfall and streamflow in the future periods. The results show that the upland recharge and channel transmission losses, and correspondingly, groundwater storages are quite sensitive to the climate change scenarios. In general, groundwater storage decreases for the historical period and increases for the far future period for the HadCM3 simulations, with the reverse occurring for the MPI-ECHAM5 simulations.