You are here:
STREAM RESTORATION STRATEGIES FOR REDUCING RIVER NITROGEN LOADS
Citation:
CRAIG, L. S., M. A. PALMER, D. C. RICHARDSON, S. FILOSO, E. BERNHARDT, B. BLEDSOE, M. W. DOYLE, B. HASSETT, P. M. GROFFMAN, S. S. KAUSHAL, P. M. MAYER, AND S. M. SMITH. STREAM RESTORATION STRATEGIES FOR REDUCING RIVER NITROGEN LOADS. DOI: 10.1890/070080, S. Silver (ed.), FRONTIERS IN ECOLOGY AND THE ENVIRONMENT. Ecological Society of America, Ithaca, NY, 6:1-11, (2008).
Impact/Purpose:
Provide the best management practices available to offer the greatest opportunity to reduce nitrogen movement downstream.
Description:
Despite decades of work implementing agricultural and urban best management practices to reduce the movement of excess nitrogen (N) from the land to aquatic ecosystems, the amount of N moving down streams and rivers remains unacceptably high in many watersheds. During this same time period, stream restoration has become increasingly popular, yet efforts to quantify the N-removal benefits of restoration are only now beginning. Because natural resource managers cannot put projects on hold until more data are available, they are asking scientists to use the best available knowledge to provide advice that will maximize chances of reducing the downstream flux of N. We propose a framework for prioritizing sites for management and restoration that involves identification of N sources, mode of delivery to streams, timing of delivery, and stream size. Initial screening of sites should be based on knowledge of the magnitude of potential N loads which is largely controlled by land use. Next, the relative rates of nitrogen transmission to streams in these high load regions should be estimated based on knowledge of climate, hydrologic conditions, and subsurface litho-geochemistry. If the dominant flow paths to streams are through slow moving, deep groundwater paths, less N is likely to reach streams than in regions dominated by overland or shallow subsurface flows. Thus, on a regional basis, managers could begin the prioritization process by overlaying hydrogeologic maps and physiographic data with land use data. Within a priority region, small streams (1st-3rd order) that export the majority of N during low flows offer the greatest restoration opportunities and should be targeted. Restoration channel designs should focus on optimizing in-stream carbon availability, increasing contact between the water and benthos, and improving connections between streams and adjacent terrestrial environments. A multi-pronged approach that combines stream restoration with land-based best management practices offers the greatest opportunity to reduce N movement downstream.
