Flows, Concentrations and Nitrogen and Phosphorus Fluxes in Urban Watersheds of the Gwynns Falls and Gunpowder River

Ken Belt, US Forest Service/Baltimore Ecosystem Study
Lawrence Band University of North Carolina
Gary T. Fisher, US Geological Survey
Mark Colosimo, US Army Corps of Engineers/Johns Hopkins University

Flows, concentrations and fluxes of Nitrogen and Phosphorus measured at the Baltimore Ecosystem Study's (BES) stream sampling stations along the Gwynns Falls urban-rural gradient and reference stations in the Gunpowder Watershed from water years 1999 and 2000 are discussed. The BES stream monitoring network includes watersheds at three scales, arrayed in a hierarchical design with forested, agricultural, suburban and urban land uses. A relation between land use and annual N load was apparent at some sites. However, the heterogeneous nature of urban watersheds was also revealed in this sampling of the urban hydrologic environment, attesting to the complex hydraulic system and land-water linkages that are likely to be operating. Urban sites with relatively low nutrient loads, suburban sites with high nutrient loads, watersheds with potentially high nitrogen retentions as well as watersheds with unusual water yields are among the measured values that ran counter to what had been hypothesized. Discussion of potential sources of nutrients in the urban landscape and their relation to urban hydrology will be discussed.

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