This paper describes the use of remote sensing, Geographic Information System (GIS), and a distributed hydrologic and water quality model Soil and Water Assessment Tool (SWAT) for assessing the rainfall-runoff and sedimentation load in multiple watersheds. In this study, necessary data sets representing land uses, hydrology, weather, soils, elevation, and surface characteristics were integrated in a GIS in tabular, vector and grid formats. The land use maps that were derived from Lands at-5 TM imagery using a combination of different classification strategies, gave an average accuracy of 95%. Results from the data analysis have shown that the model is able to predict the stream flow and sedimentation load satisfactorily, even after seven years of calibration. Based on the hydrological simulation results obtained, the SWAT model appeared to satisfactorily represent the hydrologic response of a river basin, and it can be used for long-term river basin management.

Over the years, Malaysia has undergone rapid development with subsequent population growth, urbanization, industrialization, logging activities, and expansion of agricultural areas. These changes have caused complex environmental problems and the most affected is water resources. Inherent in the solution of the above problem and many environmental problems is the need to bring together dispersed geographical data sets. The complexity and size of these databases make the application of Geographic Information System (GIS) and remote sensing technology all the more necessary. By bringing key data and analytical components together under a GIS environment, the problems of lack of integration, limited coordination, and time-intensive execution, typical of the more traditional watershed assessment tools faced by most users can be overcome.

Rising concern about the degradation of environment, such as river water quality, justifies the use of remote sensing data as input in a GIS environment. The objective is to simulate streamflow and suspended sediment from multiple watersheds using Soil and Water Assessment Tool (SWAT), a GIS-interface physical-based hydrological model. To achieve the above objective, the Upper Bernam River Basin (UBRB), located in southeastern part of the Perak state, Malaysia was chosen for this study.

SWAT model is the continuation of a long-term effort of nonpoint source pollution modeling by the US Department of Agriculture (USDA)-Agricultural Research Service (ARS), developed by Neitsch et al. (1999) is a well-established GIS-interface physically-based model, which operates in a daily time step.

Environmental Sciences Journal, SWAT Hydrological Model, Upper Bernam River Basin, Malaysia, Soil and Water Assessment Tool, Geographic Information System, Water Resources, Remote Sensing Technology, Agricultural Research Service, Universal Soil Loss Equation, GIS Database, Landsat Thematic Mapper Imageries, Meteorological Data, Government Departments.