An update to Topmodel: incorporation of soil and land use spatial variations

Abstract

Spatial variations of the land use and soil properties in a catchment can significantly affect the runoff generation. However, incorporation of basin land use and soil variations into some distributed hydrological models mostly seems resulting in a problem of over parameterization of hydrological processes, and the simulation performances might not superior to semi-distributed or even lumped hydrological models. In the late 1970s, Topmodel was developed by using a simple and effective manner, topographic index, to simulate the topographic influence on runoff generation, and the model is regarded as a semi-distributed hydrological model. Topmodel has been used successfully to many river basins in the world. In the middle 1980s, a study developed an updated topographic index to include basin soil spatial variation. Nevertheless, application of the updated topographic index has not been seen yet. Moreover, the land use normally varies considerable in a basin, and can affect runoff generation through influencing rainfall interception, infiltration, overland flow and evapotranspiration. Therefore, this study will explore the way of integrating the variations of the land use and soil properties into the topographic index, and it is expected that an update to Topmodel be achieved. Then, the updated Topmodel will be used to simulate runoff generation in a headwater catchment in Hong Kong.