Landscape-Scale Patterns in the Capacity of Riparian Buffers to Reduce Stream Nutrient and Sediment Loads

Riparian buffers have the potential to reduce nutrient and sediment loads in streams. This load reduction potential varies among watersheds and describes the utility of buffers as a management practice. We present a model for estimating sediment and phosphorus load reduction potential at the spatial grain of the small watershed. Load reduction potential is the current load minus the sum of unbufferable sources. We built regression models from measured annual loads and landscape metrics to estimate current annual loads. Unbufferable sources cannot be attenuated by riparian buffers and include point sources, fine-textured soils, and meander belt erosion. We estimate the model parameters for a set of 1600 small (average 52 sq. km) watersheds in Wisconsin. Sediment and phosphorus load reduction potential estimates are used rank these watersheds according to their suitability for riparian buffer implementation. A sensitivity analysis indicates that watershed ranks are moderately robust to errors in model parameters. This application is part of a geographic targeting scheme that seeks to invest conservation funds where water quality can be most improved.