Predicting nutrient and sediment loadings to streams from landscape metrics: A multiple watershed study from the United States Mid-Atlantic Region

There has been an increasing interest in evaluating the relative condition or health of water resources at regional and national scales. Of particular interest is an ability to identify those areas where surface and ground wa ters have the greatest potential for high levels of nutrient and sediment l oadings. High levels of nutrient and sediment loadings can have adverse eff ects on both humans and aquatic ecosystems. We analyzed the ability of land scape metrics generated from readily available, spatial data to predict nut rient and sediment yield to streams in the Mid-Atlantic Region in the Unite d States. We used landscape metric coverages generated from a previous asse ssment of the entire Mid-Atlantic Region, and a set of stream sample data f rom the U.S. Geological Survey. Landscape metrics consistently explained hi gh amounts of variation in nitrogen yields to streams (65 to 86% of the tot al variation). They also explained 73 and 79% of the variability in dissolv ed phosphorus and suspended sediment. Although there were differences in th e nitrogen, phosphorus, and sediment models, the amount of agriculture, rip arian forests, and atmospheric nitrate deposition (nitrogen only) consisten tly explained a high proportion of the variation in these models. Differenc es in the models also suggest potential differences in landscape-stream rel ationships between ecoregions or biophysical settings. The results of the s tudy suggest that readily available, spatial data can be used to assess pot ential nutrient and sediment loadings to streams, but that it will be impor tant to develop and test landscape models in different biophysical settings .