Evaluation of best management practices (BMPs) for mitigating non-point source pollution in the Wang River Basin of Thailand based on the SWAT Model

Non-point source pollution is one of the major contributors to water pollution. Unveiling the spatiotemporal distribution characteristics of non-point source pollution and selecting appropriate best management practices (BMPs) are crucial for the effective control of water pollution and the sustainable utilization of water resources. This study focuses on the Wang River Basin in Thailand, employing the calibrated and validated Soil & Water Assessment Tool (SWAT) model to evaluate the implementation of BMPs. Cost-effectiveness (CE) assessments were conducted for two interception measures - vegetative filter belts and grassed waterways - to identify the most suitable BMPs for the basin. The results demonstrated that the SWAT model successfully captured the spatial and temporal dynamics of pollutant transport, with satisfactory R² and NS values for both river discharge and pollutant load simulations. Both BMPs effectively reduced non-point source pollution; the grassed waterway achieved average reduction rates for ammonia-N and total phosphorus (TP) of over 15 %, while the vegetative filter belt reached 24.9 % and 33.1 % for ammonia-N and TP, respectively. In terms of cost-effectiveness, although vegetative filter belts exhibited higher pollutant reduction rates, grassed waterways provided a better balance between cost and performance, with the highest CE values for ammonia-N and TP reaching 0.49 and 2.46, respectively. These findings offer practical insights and a data foundation for future efforts to mitigate non-point source pollution in the Wang River Basin. • The initial application of Best Management Practices in the Wang River Basin, Thailand. • Successful application of the SWAT Model in the study of Best Management Practices. • Interception measures have shown significant effects in controlling non-point source pollution. • The grassed waterway is more suitable for Wang River Basin from cost-effectiveness perspective.