Urban Stream Restoration Effects On Water Quality and Quantity.

In 2001 research began on Minebank Run, an urban stream in Maryland, USA to examine the impacts of stream channel restoration.  These research results depict the restoration effects on ground water and surface water quality and quantity.  The study reach was downstream of the Baltimore I-695 Beltway and was restored in 2004/05 using natural channel design to restructure portions of the stream channel banks.  Restoration goals included stream channel redevelopment to contain runoff from storm events.  Restoration modified the undercut stream banks and was expected to alter in-channel storage.  Stream gauges and piezometers were installed in the stream channel and floodplain along multiple transects to monitor hydrology and water quality.  Groundwater quality significantly differed after the restoration in some of the wells in a restructured area; sodium concentrations significantly decreased in the wells directly after restoration followed by a significant increasing trend in both sodium and chloride.  It is unknown if these increasing trends will stabilize at the pre-restoration concentrations, however, if the increasing trend in the surface water salinity is indicative, then well water trends are also expected to persist and possibly increase.  Storm event precipitation induced specific conductivity spikes with elevated salinity levels indicative of first flush runoff.  Salinity levels reached approximately one-third of sea water during these events.  Comparisons of the pre- and post-restoration period hydrographs and associated precipitation events indicate that there was a decrease in peak storm discharges after restoration.  An altered hydrology has implications for other locations and supports the implementation of green infrastructure by detaining in-channel water.  Improved in-channel detention has implications for wastewater treatment plants with combined sewer overflows and has the potential to help limit untreated releases.  Therefore, the benefits of stream restoration and subsequent improvements to ecosystem services can affect human and environmental health.