Improving the streamflow simulations of a data-poor mountainous watershed using parameter transfer based on similar land use and land cover

Developing a hydrological model for the Himalayan region is challenging due to the limited availability of streamflow data. Model parameters can be transferred from similar gauged basins; however, identifying similar catchments is difficult in complex mountainous terrains. We used the WATFLOOD hydrological model, which is based on the Grouped Response Unit (GRU) for parameter transfer. This method requires that the gauged basin shares similar land use and land cover types with the ungauged one. The Koshi River basin in Nepal was identified as a suitable donor basin due to its adequate streamflow data. The sensitivity analysis shows that the lower zone exponent (pwr) is the most sensitive parameter. Using the parameters from the donor basin, we observed a significant improvement in the WATFLOOD output. The R2, NSE, and KGE values improved from 0.53, -1.87, and -0.36, to 0.72, 0.69, and 0.66, respectively. This method is reliable and efficient for mitigating data constraints in hilly catchments.