The primary goal of this research project was to employ a suite of state-of-the-art hydrologic methods to assess the aggregated, watershed-scale effectiveness of using green stormwater infrastructure as part of new suburban residential development in north-central Howard County, Maryland. The field-based study was conducted over 5½ years (2019-2025) on a small (0.31 mi 2 ) watershed drained by an unnamed tributary to the Little Patuxent River; runoff and water quality responses were monitored through 1) the “pre-GSI” period, 2) the period “during GSI” implementation, and the “post-GSI” period of development. An adjacent watershed (Plumtree Branch, 0.82 mi 2 ), developed using traditional stormwater management, was used as a hydroclimatic control.
Both watersheds were gaged using conventional methods; storm hydrographs were separated (i.e., old water, new water) using 5-min conductivity data; the separations were used to calibrate a recursive digital filter to estimate the baseflow index. Gage-adjusted, areal storm rainfall was based on a NEXRAD WSR-88D rainfall product. Two hundred individual storm events were characterized over the course of the study. In addition, monthly baseflow grab samples and automated stormflow samples from 50 events were analyzed for 16 different water quality constituents including nutrients (N, P), suspended solids, chloride, and specific conductance; the water quality data were used to compute discharge-weighted event mean concentrations and event loads for each watershed, while two different loading models were used to estimate monthly and annual loads. Preliminary statistical analyses have demonstrated numerous differences in response between the two watersheds, but the ability to detect “GSI signals” in the data appears to be hindered by very high hydroclimatic variability over the course of the study.
Speaker Bio:
Keith N. Eshleman
Professor at the University of Maryland Center for Environmental Science and is based at Appalachian Laboratory in Frostburg, Maryland. Dr. Eshleman’s research interests are in the areas of watershed and wetlands hydrology; groundwater/surface water interactions; biogeochemical processes in upland and wetland ecosystems; water quality modeling; and ecosystem responses due to natural disturbances, energy development, and land use change. Eshleman’s field-oriented research program has broadly focused on man’s impacts on the hydrologic cycle, specifically on examination of the hydrological effects of acid deposition, forest disturbances, surface mining, shale gas development, urban stormwater management, and peatland drainage and restoration.
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