A comparison of parameter estimation for distributed hydrological modelling using automatic and manual methods

Distributed hydrological models have become the main tool to study the hydrology natural law and solve the hydrology practice question. However, the definition of model parameter values limits their application. Manual calibration is time consuming and often tedious, and the automatic calibration method could be an innovative way of improving the traditional model fitting procedure. PEST is designed for easy linkage with other models and has been applied to many distributed hydrological model. Therefore, the PEST model is selected in this paper to link with the WATLAC model and calibrate the parameters, and compare the calibration results with manual results. The results show that the difference of two group parameter values is obvious. The PEST model can easily drive the WATLAC model and gain the optimal parameter values efficiently. The WATLAC model produces an overall good fit, the Ens values, except in 2001, are more than 0.83 and with an average of 0.93. But the relative runoff depth errors are larger slightly than manual results. The simulated stream flow hydrographs with PEST demonstrated a closer agreement with the observed hydrographs, while, the model simulation using manual calibration method behaved not very well and there was a tendency for the model to enlarge the peak flows.