Landscape Planning for Agricultural Nonpoint Source Pollution Reduction III: Assessing Phosphorus and Sediment Reduction Potential |
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Authors: | Matthew W Diebel Jeffrey T Maxted Dale M Robertson Seungbong Han M Jake Vander Zanden |
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Institution: | (1) Center for Limnology, University of Wisconsin, 680 N. Park Street, Madison, WI 53706, USA;(2) US Geological Survey, Wisconsin Water Science Center, 8505 Research Way, Middleton, WI 53562, USA;(3) Statistics Department, University of Wisconsin, 1300 University Avenue, Madison, WI 53706, USA |
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Abstract: | Riparian buffers have the potential to improve stream water quality in agricultural landscapes. This potential may vary in
response to landscape characteristics such as soils, topography, land use, and human activities, including legacies of historical
land management. We built a predictive model to estimate the sediment and phosphorus load reduction that should be achievable
following the implementation of riparian buffers; then we estimated load reduction potential for a set of 1598 watersheds
(average 54 km2) in Wisconsin. Our results indicate that land cover is generally the most important driver of constituent loads in Wisconsin
streams, but its influence varies among pollutants and according to the scale at which it is measured. Physiographic (drainage
density) variation also influenced sediment and phosphorus loads. The effect of historical land use on present-day channel
erosion and variation in soil texture are the most important sources of phosphorus and sediment that riparian buffers cannot
attenuate. However, in most watersheds, a large proportion (approximately 70%) of these pollutants can be eliminated from
streams with buffers. Cumulative frequency distributions of load reduction potential indicate that targeting pollution reduction
in the highest 10% of Wisconsin watersheds would reduce total phosphorus and sediment loads in the entire state by approximately
20%. These results support our approach of geographically targeting nonpoint source pollution reduction at multiple scales,
including the watershed scale. |
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Keywords: | Riparian buffers Nonpoint source pollution Land cover Phosphorus Sediment Prioritization |
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