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EFFECTS OF HYDROLOGY ON NITROGEN PROCESSING IN A RESTORED URBAN STREAM
Citation:
STRIZ, E. A., P. M. MAYER, E. DOHENY, AND R. STARSONICK. EFFECTS OF HYDROLOGY ON NITROGEN PROCESSING IN A RESTORED URBAN STREAM. Presented at Chesapeake Bay Program Workshop "Quantifying the Role of Stream Restoration in Achieving Nutrient and Sediment Reductions.", Laurel, MD, November 14, 2006.
Impact/Purpose:
To inform the public.
Description:
In 2001, EPA undertook an intensive research effort to evaluate the impact of stream restoration on water quality at a degraded stream in an urban watershed. An essential piece of this comprehensive study was to characterize, measure and quantify stream ground water/ stream water interaction (GSI) before and after stream restoration. The main goal was to evaluate if particular stream restoration techniques improve GSI so that beneficial interaction between the stream and riparian/ flood plain such as nutrient processing may be enhanced. The objectives to meet this goal were to establish effective and efficient techniques to measure and quantify the GSI before and after restoration, identify those geomorphic and geological factors which control GSI, and evaluate if specific restoration techniques enhance GSI. In the first phase of the study, intensive hydrological measurements were made at several temporal and spatial scales around particular stream features slated for restoration. These measurements were used to describe the near stream flow field. Storm surges were also evaluated using hydrologic parameters and temperature to assess and quantify their impact on GSI. Finally, the pre-restoration GSI was calculated for each stream feature using a simple transparent method to quantify GSI over the temporal and spatial scales of interest. Residence times were determined in stream bed and banks. The second phase of the study is still in progress and will establish the GSI after stream restoration using the same methods. Once the GSI is effectively characterized and quantified, the pre and post restoration flow can be used with measured denitrification rates to predict the mass removal of nitrate for each phase. This will lead to a true assessment of the impact of restoration on water quality. These studies are intended to provide restoration designers and stakeholders with practical methods to measure GSI and identify specific restoration techniques which improve GSI to enhance all beneficial stream functions.