Simulation of rainfall–runoff processes in karst catchment considering the impact of karst depression based on the tank model

Abstract

Karst depressions play an important role in runoff generation and concentration processes of karst catchments. Storm water tends to be stored in karst depressions firstly before routing to the catchment outlet. However, simulating methods of runoff processes considering the impact of karst depressions are rarely reported. To fill this concept and technology gap, we propose a conceptual hydrological model considering the role of karst depressions in this study. A three serial tank model coupled with two soil tanks is established at each grid in each subcatchment, to simulate surface runoff, interflow, groundwater runoff, and soil moisture dynamics. During the process of flow concentration, surface runoff from each grid is reduced by karst depressions at its lower reach. The surface runoff loss is controlled by the area ratio of karst depression and corresponding subcatchment. River channel routing is carried out based on the Muskingum approach. The conceptual hydrological model is further calibrated and validated over the Hamajing catchment, a small karst catchment in Hubei Province, China. Results show that the proposed model can generally reproduce the runoff generation and concentration processes well. Nash-Sutcliffe efficiency (NSE) coefficient is 0.85 during the calibration period and 0.78 in the validation period. Root mean squared errors are 6.24 m3/s and 5.35 m3/s during calibration and validation periods respectively. Sensitivity analysis indicates that the parameters related to the first tank are most sensitive to the simulation results, whereas the change of parameters related to the second and third tanks cannot significantly influence the simulation results. Additionally, the area ratio of karst depression has great influence on the runoff processes in karst catchment. This proposed conceptual model provides a simple approach to simulate the hydrological processes in karst region.