Effects of Topographic Heterogeneity on Coarse Resolution Grid-Based Runoff Simulation—Assessment for Three River Basins in Peninsular Malaysia

This paper investigates the effects of topographic heterogeneity on the runoff response simulated by a 0.05 degree (approximately 5.5 km) spatial resolution distributed hydrological model for the Pahang, Kelantan, and Muda river basins (25,600, 11,900, and 4010 km², respectively) in Peninsular Malaysia. Daily simulations were carried out and assessed against observed streamflow for the period 1999–2004. Topographic structure was characterized by means of subgrid terrain slope to guide the decomposition of hydrological parameters over the model grid. The results show improved simulation skill for all three basins compared to a traditional runoff production parameterization scheme that does not take into account the subgrid topographic variability. However, other factors related to morphological heterogeneity and variability in physical terrain conditions should be considered in future work in order to characterize the hydrological heterogeneity. The present methodology may be of potential for further development of large-scale, coarse resolution grid-based hydrological models without adding structural model complexity and without affecting parameter parsimony.