Acheiving Phosphorus Load Reductions: Lessons from a Successful Watershed Project.

A project in southwestern Wisconsin has shown that producers’ changes in management can lead to improvements in stream water quality. Two watersheds, both approximately 19 mi², with a similar mix of agriculture, grasslands and woods and similar soils and topography, were selected for the project. The streams at the outlets of the two watersheds have been monitored for flow, phosphorus and sediment since September 2006. One of the watersheds was picked for targeted conservation efforts, while the other was used as a reference. Having a nearby reference watershed without any special conservation efforts allowed us to determine how the project itself affected water quality without having the results obscured by variations in weather and regional land management trends. The project watershed was inventoried to locate areas that were contributing comparatively high amounts of sediment and nutrients to the stream. The tools used for identifying high loss areas were the Revised Universal Soil Loss Equation 2 (RUSLE2) and the Wisconsin Phosphorus Index in the SnapPlus nutrient management.  Dane County Land Conservation staff also used a barnyard model to rank barnyards by their potential phosphorus runoff. Using these inventories, the project identified ten operations estimated to be contributing the most total phosphorus in surface runoff to the streams. Eight of the ten focus operations began working with the project in 2010, and one joined in later.  They implemented a combination of in-field and off-field practices to reduce runoff phosphorus and sediment losses with cost-share funding from the NRCS and The Nature Conservancy. The main field management changes were no-till/reduced tillage and pasture/lot systems, and participating farmers cut their operations’ estimated erosion and phosphorus delivery by half.  In 2013 and 2014, the first two years after full implementation, there was a 37 % statistically significant (α = 0.1) reduction in phosphorus runoff event loads in the project stream compared to the reference stream. This project showed that it is possible to achieve water quality improvements in a relatively short time frame by focusing conservation efforts.