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Title: OPTIMIZING THE PLACEMENT OF RIPARIAN PRACTICES IN A WATERSHED USING TERRAIN ANALYSES

Author
item Tomer, Mark
item James, David
item ISENHART, THOMAS - IOWA STATE UNIVERSITY

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2003
Publication Date: 7/25/2003
Citation: TOMER, M.D., JAMES, D.E., ISENHART, T.M. OPTIMIZING THE PLACEMENT OF RIPARIAN PRACTICES IN A WATERSHED USING TERRAIN ANALYSES. JOURNAL OF SOIL AND WATER CONSERVATION. 2003. V. 58(4). P. 198-206.

Interpretive Summary: Riparian buffers and constructed wetlands are two best management practices (BMPs) that receive public support through USDA programs because they can improve water quality. But these practices are not equally effective in all locations. We have developed mapping methods to strategically place riparian BMPs in a watershed to improve water quality. In a test watershed, we used publicly available data to map streambank locations where buffers have the greatest potential to intercept runoff. We also mapped candidate sites where constructed wetlands could treat tile-drainage waters. A field review with local conservation professionals confirmed the utility of the maps. Buffer sites were numerous, usually small, and distributed across the watershed. Therefore, in the case of buffers, watershed assessment technologies would not necessarily place the burden of conservation investments on a small group of landowners, but rather could help reveal strategies to share these investments effectively. But, an analysis aimed to identify sites for constructed wetlands under Iowa's Conservation Reserve Enhancement Program identified only 12 sites, including three that were prioritized through the field review. Here the analysis identified a small set of sites where a few landowners could potentially provide pollution-control services to their upslope neighbors. Because the methods only rely on public data they are readily applicable to other watersheds. These techniques could help producers efficiently achieve environmental goals, and could help conservation and environmental agencies prioritize conservation investments at watershed and farm scales, or evaluate configurations of existing BMPs.

Technical Abstract: Riparian buffers and constructed wetlands are two best management practices (BMPs) that can improve water quality and receive public support. However, these practices are not equally effective in all locations. Our objective was to develop methods to strategically place riparian BMPs in a watershed to improve water quality. Tipton Creek, a 50,000-acre Iowa watershed, provided a case study. For riparian buffers, hydrologic modeling of topographic data identified streambank locations with a high wetness index, where runoff should occur as distributed flows. To treat tile-drainage, candidate sites for constructed wetlands were identified using interpretive and automated techniques. A set of maps was produced and a field review was carried out with local conservation professionals. The buffer maps typically highlighted riparian areas where runoff from significant areas could be slowed by buffers to encourage infiltration. These sites were numerous, usually small (<300 m of streambank) and distributed across the watershed. Considering current practices, several new buffers were recommended. Wetland maps identified 12 potential wetlands, including three prioritized by review participants. The methods only required existing public data, and are applicable to other watersheds to prioritize conservation investments at watershed and farm scales, or evaluate configurations of existing practices.