ASSESSMENT OF GRASSED WATERWAY IMPLEMENTATION USING ACPF AND SWAT MODELS

Agriculture is the largest contributor of nonpoint source pollutants in US waterways, with sediment being the most prevalent cause of impairments. Sediment loss mitigation occurs through Best Management Practices (BMPs), such as grassed waterways. Federal and state agencies incentivize the implementation of BMPs through cost-share programs for farmers. The investment of public funds has increased pressure to demonstrate the effectiveness and value of individual projects, necessitating the development of strategies for prioritizing projects based on the sensitivity of particular sites to sediment erosion and optimal locations for implementation.

This study has three primary objectives: (i) document existing locations of grassed waterways, (ii) identify appropriate potential locations for grassed waterways, (iii) locate critical source areas of sediment erosion in the watershed.

Appropriate locations for grassed waterways were modelled using the Agricultural Conservation Planning Framework (ACPF) toolset. Preliminary results have been obtained for two subwatersheds in southeastern Minnesota: Bridge Creek and Crystal Creek. Bridge Creek has 140 existing grassed waterways, which may or may not coincide with optimal model locations. There were 246 potential locations identified; 13.01% of the identified locations have existing grassed waterways. Crystal creek has 194 existing grassed waterways, and 479 potential locations of which 26.93% have the practice in place. In the analyzed subwatersheds an average of 80.03% of the potential locations are undeveloped.

The Soil and Water Assessment Tool (SWAT) will be used to calculate sediment yield throughout the watersheds. Using these results, locations will be prioritized based on sensitivity to sediment erosion and potential locations for grassed waterways. Results from this study will assess if a combination of two models produces a viable prioritization framework, and if the process is applicable for watershed management decisions in other locations.