Evaluation of Best Management Practices (BMPs) For WES Conservation in an Agricultural Watershed

Implementation of best management practices (BMPs) is essential for conservation of soil and water resources, and for preventing degradation of water related ecosystem services (WES) in agricultural watersheds. Assessment of effectiveness of BMPs to mitigate problems due to erosion and peak runoff at watershed scale can be performed through scenario analyses in hydrological models such as Soil and Water Assessment Tool (SWAT). In this study, we performed spatial assessment of vulnerability of a small watershed (Jambhira) located in eastern part of India to erosion and sediment loading, in order to evaluate the effectiveness of few BMPs to mitigate the negative impacts of erosion. We utilized the SWAT model to simulate watershed management options such as grassed waterways, terracing, filter strips, strip contour cropping and stream bank stabilization as BMPs. After identifying critical soil erosion prone areas in the study watershed, BMPs are implemented targeting a decrease in sediment output, minimizing loss of nutrients, and lowering of peak runoff from the watershed. In a similar manner, critical reach sections are also determined for implementing suitable BMPs. Out of 21 sub basins of the study watershed, 14 sub basins fall under category of “very high” soil erosion (sediment yield is 20-40 t/ha/yr) and among these 14 sub basins, the reach corresponding to 6 sub basins have a significant sediment concentration. Thus, BMPs are implemented in the six critically soil erosion prone sub basins that constitute 34.29% of watershed area. Based on the geography and land use of the study watershed, we found the land management operations: contour farming and strip contour cropping, and channel restoration strategies: buffer strips and grassed waterways, as most suitable. After implementation of contour farming and strip contour cropping, it is seen that the critical sub basins have moved from “very high” to “high” and “moderate” soil erosion categories thus leading to improved WES in the area. Based on simulated results, the effectiveness of strip contour cropping is found to be higher than contour farming in reducing sediment yield of the study watershed. With additional interventions proposed for reach management in this watershed, it is possible to reduce negative effects of erosion substantially.

Key words: Best Management Practices, Soil Erosion, Soil and Water Assessment Tool, Watershed Conservation, Sediment Yield