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ASSESSMENT OF NEAR-STREAM GROUND WATER-SURFACE WATER INTERACTION (GSI) OF A DEGRADED STREAM BEFORE RESTORATION
Citation:
STRIZ, E. A. AND P. M. MAYER. ASSESSMENT OF NEAR-STREAM GROUND WATER-SURFACE WATER INTERACTION (GSI) OF A DEGRADED STREAM BEFORE RESTORATION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-07/058, 2007.
Impact/Purpose:
To detect geomorphic characteristics and geomorphic changes over time in a selected area.
Description:
In Fall 2001, EPA undertook an intensive collaborative research effort with the USGS and the Institute of Ecosystem Studies (IES) to evaluate the impact of restoration on water quality at a degraded stream in an urban watershed using a before/after stream restoration study design. One objective was to evaluate if particular stream restoration techniques improve ground water-surface water interaction (GSI) so that beneficial exchanges between the stream and riparian/ flood plain which improve water quality may be enhanced. An essential piece of this comprehensive study was to characterize, measure, and quantify near-stream (GSI) before and after stream restoration at specific stream features and assess how the geomorphology and geology at each feature impact GSI. This research brief describes the pre-restoration study of GSI at specific stream features in a degraded urban stream in Towson, MD. The study employed a comprehensive evaluation of the surface water hydrology, ground water hydrology, geomorphology and geology along a specific stream reach slated for restoration. Ground water level measurements in piezometer nests in the stream bed and banks over time were found to be sufficient to characterize the losing or gaining nature of near-stream GSI. Temperature measurements were used to verify these interactions. The GSI was simply and effectively quantified using gradients calculated from the piezometer nest ground water levels and Darcy’s law in a simple compartment model. Once the flow was quantified, it was used to calculate residence times in the sediments. These residence times may be used to quantify the mass removal of nutrients and other contaminants if reaction kinetics are known. The results of the pre-restoration study reveal the highly variable nature of GSI on the temporal and spatial scales of interest. They also reveal how specific stream features and settings influence GSI. Flow and residence time were found to be very dependent on the stream feature geology and geomorphology. It is anticipated that any restoration which impacts these features will strongly influence GSI. The results of this study established the pre-restoration GSI. An identical study of the post-restoration GSI is underway. The results will be compared to the pre-restoration state in a second report to evaluate the impact of stream restoration on GSI to determine if improvements in water quality may be achieved.
URLs/Downloads:
ASSESSMENT OF NEAR-STREAM GROUND WATER-SURFACE WATER INTERACTION (GSI) OF A DEGRADED STREAM BEFORE RESTORATIONURL.PDF (PDF, NA pp, 24 KB, about PDF)
PRE-RESTORATION GEOMORPHIC CHARACTERISTICS OF MINEBANK RUN, BALTIMORE COUNTY, MARYLAND, 2002-04
