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EFFECTS OF STREAM RESTORATION ON GROUND WATER NITRATE AT MINEBANK RUN, AN URBAN STREAM IN THE CHESAPEAKE BAY WATERSHED
Citation:
MAYER, P. M., E. A. STRIZ, P. M. GROFFMAN, E. DOHENY, AND R. SHEDLOCK. EFFECTS OF STREAM RESTORATION ON GROUND WATER NITRATE AT MINEBANK RUN, AN URBAN STREAM IN THE CHESAPEAKE BAY WATERSHED. Presented at SETAC Conference, Baltimore, MD, November 14 - 17, 2005.
Impact/Purpose:
To inform the public.
Description:
Elevated nitrate levels in streams and ground water pose human and ecological threats. Microbial denitrification removes nitrate from ground water but requires anaerobic (saturated) conditions and adequate supply of dissolved organic carbon from detritus and organic soils. Conditions favorable for denitrification may be under geomorphic control. For example, stream incision due to urbanization may cause a disconnection between the stream channel and the adjacent floodplain thereby inhibiting denitrification and/or promoting nitrification. We examined the effects of geomorphic restoration (e.g. bank re-shaping, bank reinforcement, channel meanders, energy dissipation structures) on ground water nitrate and carbon of Minebank Run, a restored urban stream in the Chesapeake Bay watershed. Nitrate was inversely related to dissolved organic carbon in ground water, suggesting control of denitrification by carbon availability to microbial denitrifiers. Nitrate concentration was positively related to dissolved oxygen in ground water, suggesting that lower base flow and increased hydraulic residence times, promoted conditions (e.g. lower dissolved oxygen, prolonged mixing with dissolved organic carbon) that removed N from the stream. Nitrate was lower in restored reaches of the stream in which incised banks had been reconstructed, suggesting that stream restoration methods that reconnect flood plains to stream channels can promote ground water nitrate removal and, thereby, improve stream water quality.