Using SWAT to Assess the Critical Areas and Nonpoint Source Pollution Reduction Best Management Practices in Lam Takong River Basin, Thailand

Abstract

Hydrological models are essential tools for water resource and nonpoint source pollution management. This study aimed to evaluate critical areas and best management practices (BMPs) of sediment and nutrient loads in Lam Takong River basin, Northeastern Thailand, using SWAT (Soil and Water Assessment Tool) model. The model was calibrated and validated using daily data of streamflow, sediment, NO3-N and TP in Lam Takong River from 2007-2008 and 2009, respectively. In general, the simulated streamflow and sediment were in reasonable agreement with the measured values with coefficient of determination (R2) and Nash-Sutcliffe model efficiency coefficient (NSE) greater than 0.50 and the percent bias (PBIAS) less than 25%. Additionally, nutrient loads showed a fair relationship between observation and simulation with R2 values more than 0.6 and PBIAS values less than 25%. From simulation, September was the month with the highest sediment, NO3-N and TP yields while January and December were the lowest months. From the model, SWAT identified 1 severe and 1 high soil erosion subbasins. Two subbasins were classified into medium loading for NO3-N. However, 9 subbasins were classified into high loading rate of TP. For BMPs, the 30-mwide filter strip was the best scenario reducing 100% of both sediment and TP, and 97.27% of NO3-N. These results could be a useful tool for water resources managements and soil conservation planning in Lam Takong River basin.

Keywords

• hydrological model
• nitrate
• phosphorus
• soil erosion
• watershed