Institute of Ecosystem Studies

2009 BES Annual Meeting Presentation and Poster Abstracts

Inflow and Transient Storage in Urban Streams: One More Reason to Protect Riparian Forests
Ryan, Robert
Co-Authors: Claire Welty, University of Maryland Baltimore County Philip Larson, University of Maryland Baltimore County

Abstract: The influence of riparian land cover on net inflow of groundwater to streams and transient storage within the Dead Run watershed was investigated as part of the Baltimore WATERS Testbed effort. Bromide tracer injection experiments were conducted in two stream reaches under summer low baseflow (August 2007) and spring high baseflow (May 2008) conditions. Each reach was approximately 900 m long and riparian land cover, which varied by sub-reach, included forest, meadow, turf grass, and impervious surfaces. During spring high baseflow conditions, net inflow was comparable in all subreaches. However, during summer low baseflow conditions, net inflow was positive in subreaches with riparian forest cover and negative in the subreach with no riparian forest cover. The net loss of water in the subreach with no riparian cover is attributed to uptake and evapotranspiration by in-channel vegetation which was more prevalent here than in the subreaches with riparian cover. Transient storage in subreaches with the least riparian forest cover also varied with seasonal baseflow condition. During summer low baseflow conditions, in-channel vegetation observed in these subreaches acted as a transient storage zone, and transient storage was relatively high and comparable to subreaches with wide riparian forests. However, during spring high baseflow conditions, in-channel vegetation was not established and transient storage was minimal in subreaches with little or no riparian forest cover. We conclude that the open canopy associated with loss of riparian forest cover in urban watersheds enhanced in-stream vegetative growth, which contributed to seasonal flow depletion and reduced transient storage.