Understanding runoff processes using a watershed model—a case study in the Western Ghats in South India

The wet tropical Western Ghat Mountain ranges in South India present an interesting combination of meteorological and physical characteristics. The results of a watershed model analysis carried out to understand the catchment response and the relative importance of different runoff processes in the region are reported in this paper. A lumped parameter model simulating saturated source area runoff, lateral flow through pipes and the saturated zone groundwater flow, has been developed assuming that source area runoff is the only quickflow component. The model has been calibrated on seven catchments using sufficiently long records of daily data. A wide range of tests has been used to show that the model performs reliably. The influence of catchment characteristics on the relative importance of the flow components and the catchment response has been studied. The model simulations have been interpreted to infer that the pipeflow contributions augment the contributions of source area runoff to stream quickflow. Suggestions for further research in the area are given, based on the inferences drawn.