Evaluating the Efficacy of Best Management Practices in Mitigating Sediment Yield and Nutrient Losses in the Lower Sutlej River Basin, India

Soil erosion is one of the most serious environmental concerns as it threatens the sustainable agriculture and poses a grave threat to global food security. It is important to adopt the appropriate soil conservation measures to reduce the erosion hazard. In the present study, SWAT model has been applied to study the impact of various best management practices (BMPs) on sediment yield and nutrient losses from a Lower Sutlej River Basin, India. The impact of agricultural and structural BMPs was assessed both individually and in combinations to evaluate the best possible combination of BMPs. Three scenarios, viz., CT1-BMP-1 + CF-BMP-2 + CD-BMP-5 + Fertilizer level 1 (Scenario-1), CT1-BMP-1 + CF-BMP-2 + CB-BMP-3 + CD-BMP-5 + CT2-BMP-8 + Fertilizer level 2 (Scenario 2) and CT1-BMP-1 + CF-BMP-2 + CB-BMP-3 + BT-BMP-4 + CD-BMP-5 + GSS-BMP-6 + SBSS-BMP-7 + CT2-BMP-8 + Fertilizer level 3 (Scenario 3) were developed to study their impact on sediment yield and nutrient losses. The average annual sediment yield from watersheds ranges from 3.08 to 21.63 ton/ha/yr for the base scenario (without BMPs), 1.97 to 13.94 ton/ha/yr in scenario 1, 1.66 to 10.77 ton/ha/yr in scenario 2, and 1.04 to 7.78 ton/ha/yr in scenario 3. At the watershed level, the greatest decrease in sediment yield was obtained from check dam (28.72%), followed by bench terracing (25.62%), grade stabilization structures (22.74%), contour bunding (20.88%), stream bank stabilization structures (10.02%), contour trenching (8.99%), conservation tillage (6.66%) and contour farming (4.54%). The use of structural BMPs at the watershed level reduced sediment yields more effectively than agricultural BMPs. The implementation of all the potential BMPs in Scenario 3 minimized sediment yields to the extent of 66.25%. Model simulation demonstrated that a 30% reduction in fertilizer application under fertilizer scenario 3 resulted in the highest reduction in total nitrogen (24.04%), nitrate nitrogen (8.97%), and total phosphorus (11.75%). The study findings may be useful for promoting sustainable land and water resource management at the river basin level.