WATBAL - A SEMI-DISTRIBUTED, PHYSICALLY BASED HYDROLOGICAL MODELING SYSTEM

A semi-distributed, physically based hydrological modeling system, WATBAL, which accounts for the entire land phase of the hydrological cycle is described. Primary attention is given to the hydrological processes at the root zone level through a distributed, physically based approach whereas the groundwater processes are simulated in less details by use of a lumped, conceptual approach. This approach allows WATBAL to utilize spatially distributed input data to account for the spatial and temporal variability of meteorological conditions, vegetation and soil properties. WATBAL has primarily been designed as a tool for predicting the runoff from ungaged catchments and for assessing the hydrological effects of land use changes. The capability of the model for simulating ungaged catchments is tested using results from a recent feasibility study for medium size dams in Zimbabwe.