TOPMODEL Simulation of Fushan Watershed No. 2 Discharge

Understanding of streamflow generation processes in response to rainfall has been pursued over the past several decades, because this knowledge is essential for studying nutrient transport, biogeochemical processes, and forest ecosystem functioning. The major objective of this research was to simulate the flow pathways in a humid forested watershed in Taiwan. The hydrological model TOPMODEL, based on the variable-source-area concept of streamflow generation mechanism, was used to predict both amounts of saturation overland flow and subsurface flow in the Fushan watershed no. 2 (94 ha). Two periods were chosen, one each for model calibration (from July to October 1995) and model validation (from March to June 1996). Identification of the optimal parameter set was performed through the Rosenbrock algorithm. Results show that TOPMODEL is suitable for simulating streamflow in the Fushan watershed no. 2. Both model calibration and validation runs, on a daily basis, produced good fits, where model efficiencies were 0.89 and 0.82, respectively. The dominant source of streamflow generation in the study area is subsurface flow that accounts for 85.1% and 88.3% of the total simulated streamflow for the 2 periods, respectively.