Effect of slope on water run-off and soil vulnerability in an unglaciated sub-watershed: a case study of conservation practice siting

For maximization of soil and water quality benefits, the right agricultural conservation practices (CPs) should be practiced for the right place. The Agricultural Conservation Planning Framework (ACPF) is a tool that helps decision makers achieve precise conservation within a target watershed using rapid, low-cost Geographic Information System-based tools. ACPF takes the information on landscape characteristics and combines it with user input to identify locations susceptible to soil loss and water run-off and suggest potential CP locations. Suggested CPs may further be analyzed for urgency, installation cost, and effectiveness. In this study, ACPF was applied to analyze soil and water vulnerability within a small unglaciated sub-watershed in southwest Wisconsin and identify potential CP practices and recommended placement sites. To promote environmental sustainability in the agriculture sector, land managers are tasked with implementing CPs, but often lack adequate information on the most effective practice and placement strategy. Field-scale siting of CPs was achieved using high-resolution terrain derivatives and accurate simulation of the stream network. Slope disaggregation among soil loss vulnerability categories was also conducted. Greatest sources of vulnerability were associated with slope and erodibility factors, with average slope within cropped fields being 6% and erodibility being as high as 43%. Fields classified as critical for conservation had a mean slope of 7.4%. Suggested contour buffer strip (CBS) placement per field varied with slope, with steeper fields having denser placement. The results suggested that 3% of cropland could be removed from production if the recommended placement of CBS was implemented. A further 0.2% of the sub-watershed area would go to grassed waterways. The results support implementation of effective CPs based on local conditions and act as a tool to help reveal if existing practices in the sub-watershed are of a size and extent comparable to the predicted potential.