From Groundwater to the Atmosphere – a study of the Hydroclimate of the La Plata Basin

The La Plata is the second largest basin in South America, and it is the most heavily populated and economically active region of the continent. Land-atmosphere interactions are particularly important in this region, as approximately 63% of mean annual precipitation over the basin comes from continental evapotranspiration. In this sense the numerical representation of terrestrial evapotranspiration is critical for an accurate depiction of the hydroclimate of the region. However, most current land surface schemes lack a fundamental hydrologic process that regulates soil moisture and evapotranspiration: groundwater. In this presentation I will focus on our current efforts to study the hydroclimate of the La Plata using the Miguez-Macho and Fan groundwater scheme within the Noah-MP land surface model. I will present results based on continental-scale offline simulations and coupled simulations using the Weather Research and Forecast (WRF) model. Incorporating groundwater increases soil moisutre in those regions where the water table is closer to the land surface, including the western and southern Amazon and the La Plata basin. Consequently, ET is larger over the southern La Plata basin, where ET is water limited and the water table is shallow. Changes in ET subsequently affect precipitation over large portions of the study domain.