Abstract:

After reviewing the weaknesses of some of the existing hydrological models in simulating the hydrological processes for largescale catchments，a new distributed hydrologic model—WATLAC was developed.The model is gridbased adopting relatively simple mathematical formulations with a reduced number of parameters.In order to verify the capabilities of the model in terms of simulating largescale catchment with a long simulation time，Ganjiang River catchment (817 × 104 km2)，the largest subcatchment of Poyang Lake watershed，was selected as the study area in this paper.The spatial heterogeneity of the catchment was simulated by discretized grids.Based on the resolution of the surface data，a grid size of 4 km×4 km was selected in the model.Input data including surface and subsurface grid information for the model were prepared by using ArcGIS.The model was calibrated against the observed daily stream flows at Waizhou and Xiajiang stations from 1960 to 1989.In the calibration period for 1960~1969，the correlation coefficients for daily，monthly and annual stream flows at the two gauging stations varied from 081 to 093，and the NashSuttclife efficiency coefficients (Ens) were in the range of 079~099.The relative errors between the simulated and the observed runoff volume were less than 8%.In the validation period of 1970~1989，the correlation coefficients for daily，monthly and annual stream flows varied from 076 to 092，and the NashSuttclife efficiency coefficients (Ens) were in the range of 075~091.The relative errors between the simulated and the observed runoff volume were less than 2%.Results indicate that the modeled stream flows match well with the observed ones，and the model is satisfactorily tested in Ganjiang River catchment.The model may be suitable for largescale hydrological modeling，and has a good application prospect in assisting water resources management.

Key words: distributed hydrologic model, Ganjiang River catchment, Poyang Lake, WATLAC