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RESTORED STREAMS ENHANCE ABILITY TO REMOVE EXCESS NITROGEN
Citation:
MAYER, P. M. AND E. A. STRIZ. RESTORED STREAMS ENHANCE ABILITY TO REMOVE EXCESS NITROGEN. U.S. Environmental Protection Agency, Washington, DC, EPA/600/F-07/003, 2007.
Impact/Purpose:
to present information
Description:
Issue: Excess nitrogen from fertilizer, septic tanks, animal feedlots, and runoff from pavement can threaten human and aquatic ecosystem health. Furthermore, degraded ecosystems like those impacted by urbanization have reduced ability to process and remove excess nitrogen from the environment. Restoring ecological condition of streams may be a cost-effective, sustainable means to reduce nitrogen pollution in watersheds. Scientists at the Agency’s Office of Research and Development evaluated the effects of stream restoration on nitrogen removal capacity at an urban stream undergoing intensive restoration in Towson, MD. Science Objective: The objectives of research on stream restoration are to identify the natural mechanisms that control nitrogen removal in streams and to determine if stream restoration is an effective means of enhancing nitrogen removal in degraded watersheds. Research began before the study stream was restored to determine how degraded systems function to remove nitrogen. Restoration of the study stream was completed in 2005 using various techniques that reshaped the stream banks and channel, reconstructed natural stream features, and re-established riparian plants. Research continued after restoration to determine the effects of restoration practices on nitrogen removal. Research is ongoing to track long-term impacts of the restoration. The study found that restored streams more effectively removed nitrate nitrogen than unrestored streams. The capacity for streams to remove nitrate nitrogen increased when adequate supplies of organic carbon were available and when flooplain hydrology was reconnected. The total amount of nitrogen removed in restored streams can be significant and may help to reduce the total nitrogen load reaching water bodies of concern like the Chesapeake Bay. Application and Impact: This EPA research effort represents one of the most intensive efforts to date to quantify the effects of stream restoration on nitrogen processing in urban streams. Municipal natural resource agencies such as Baltimore County have already used this information to help develop regional stream restoration strategies aimed at improving ecosystem health and water quality. This research also has contributed to efforts by EPA’s Chesapeake Bay Program to model the effects of stream restoration on Bay ecosystem health. Results of this ongoing research effort on stream restoration continue to be used to develop regional and national approaches to implementing and prioritizing stream restoration to manage nitrogen in watersheds.