A coupled modeling system of the hydrologic cycle within river basins

In the Rio Grande Basin, water resources are increasingly in demand but are limited. The basin is influenced by a number of climatic regimes and the delicate balance of the water cycle within the basin could be dramatically affected by even small changes in global climate. In order to better understand the hydrologic cycle and its influence on the water resources in the Rio Grande Basin, we are developing a coupled modeling system to simulate the water balance of river basins. This modeling system incorporates existing models, including an atmospheric model to simulate the precipitation and meteorological variables, a surface hydrology model to simulate surface infiltration, runoff, and evapo-transpiration, a river model to simulate stream flows and a sub-surface hydrology model to simulate aquifer recharge and use and the interaction of the river and aquifers. This coupled system can simulate the hydrologic cycle for the current climate regime, with its natural variations, using observed global atmospheric conditions as input, or it can simulate the impact of global climate change on the hydrologic cycle, using GCM predictions of global atmospheric conditions as input.

Our recent work has concentrated on the atmosphere and surface interface for the water year 1992-1993, an El Nino year. We will present results of the atmospheric simulation of the entire year, which employed 5 km horizontal grid spacing over the upper Rio Grande basin. The predicted precipitation from this simulation is down-scaled to the 100 m grid spacing of the surface hydrology model, which calculates the runoff and soil moisture at this fine scale.