The Development and Application of Malaysian Soil Taxonomy in SWAT Watershed Model

Abstract

The concept of watershed modeling is embedded in the interrelationships of geo-spatial data and hydro-meteorological data and represented through mathematical abstractions. The behavior of each process is controlled by its own characteristics as well as by its interaction with other processes active in the catchment. The hydrological models vary from empirical models to stochastic models of various kinds and finally to the more recent distributed models. In recent years, distributed watershed models have been increasingly used to implement alternative management strategies in the areas of water resource allocation, flood control, impact assessments for land use and climate change, and pollution control. Many of these models share a common base in their endeavor to incorporate the heterogeneity of the watershed and the spatial distribution of topography, vegetation, land use, soil characteristics, and rainfall. This study attempts to provide a framework of hydrological assessment using a Malaysian soil data as a soil characteristics input in Soil Water Assessment Tool (SWAT) model in its place of using the USDA Soil Taxonomy database. This chapter reports a SWAT simulation output using a Malaysian soil data from the SWAT input file. It was found that the SWAT model can be successfully applied for hydrological evaluation of the Langat River basin, Malaysia. To the Langat River basin, SCS runoff curve number (CN), base flow alpha factor (ALPHA_BF), and groundwater delay (GW_Delay) were found to be the most sensitive input parameters. The works attempting a hydrological simulation using a local soil data directly from Malaysian soil database are still in the programming stages. A same methodology is suggested to be practiced in other open source hydrological models.