Modeling Terrestrial Hydrological Systems at the Continental Scale: Testing the Accuracy of an Atmospheric GCM

Abstract

Abstract A global hydrological routing algorithm (HYDRA) that simulates seasonal river discharge and changes in surface water level on a spatial resolution of 5′ long × 5′ lat is presented. The model is based on previous work by M. T. Coe and incorporates major improvements from that work including 1) the ability to simulate monthly and seasonal variations in discharge and lake and wetland level, and 2) direct representation of man-made dams and reservoirs. HYDRA requires as input daily or monthly mean averages of runoff, precipitation, and evaporation either from GCM output or observations. As an example of the utility of HYDRA in evaluating GCM simulations, the model is forced with monthly mean estimates of runoff from the National Centers for Environmental Prediction (NCEP) reanalysis dataset. The simulated river discharge clearly shows that although the NCEP runoff captures the large-scale features of the observed terrestrial hydrology, there are numerous differences in detail from observations. The s...