Evaluation of executable best management practices in Haean highland agricultural catchment of South Korea using SWAT

This study is to evaluate the reduction of high level nonpoint source (NPS) pollution discharges in Haean highland agricultural catchment (62.8 km2) by applying best management practices (BMPs) of vegetation filter strip installation (VFS), fertilizer control (FC), and rice straw mulching (RSM) in uplands above 600 m of elevation using SWAT (Soil and Water Assessment Tool). From the modeling results, the VFS BMP showed the best performance to reduce sediment (SS) of 16.0% for 1 m strip width up to 34.8% for 5 m strip width and total phosphorus (T-P) discharge loads of 5.1% to 21.3% from highland crop areas. The FC BMP showed the discharge loads reduction of 4.9% for 10% fertilizer reduction up to 16.4% for 30% fertilizer reduction. The RSM BMP results showed the sediment reduction of 3.0% for 6.0% runoff reduction up to 14.1% for 17.0% runoff reduction and T-P reduction of 1.3% for 6.0% runoff reduction up to 6.8% for 17.0% runoff reduction by showing negative effect of total nitrogen (T-N) up to −3.7% for 12.0% runoff reduction. However, because of the difficulties to install vegetation filter strip by farmers unwillingness in South Korea, the BMPs combination of fertilizer reduction and rice straw mulching (FC + RSM) was suggested as an executable BMP to obtain positive removal efficiency for all nutrient discharge loads. The FC + RSM BMP showed sediment, T-P, and T-N reductions up to 9.7%, 8.1%, and 9.2% respectively.