2005 BES Annual Meeting Presentation and Poster Abstracts
Hydraulic conductivity and hyporheic exchange in Indian Creek, an urban stream
Robert J. Ryan, Michel C. Boufadel (Temple University)
Abstract: Conservative solute tracer experiments are commonly used to estimate solute transport and transient storage characteristics of relatively pristine streams. In urban streams undergoing relatively fast geomorphic and hydrologic changes, it is also important to understand the influence of hydraulic conductivity on transport and storage characteristics. We conducted a conservative solute tracer experiment in Indian Creek, a small urban stream located in Philadelphia, Pennsylvania. As part of the experiment, we first surveyed the stream topography at a 1m resolution. During the tracer experiment, in addition to monitoring the surface water, we sampled bankside wells and small diameter wells installed in the wetted channel and in a large gravel bar. Post-experiment, we measured in situ streambed hydraulic conductivity at two depths (7.5 cm below the streambed and 10 cm below the streambed). Our results indicate that the hyporheic pathways within Indian Creek extend vertically more than 7.5 cm below the streambed and laterally as much as 8 m from the wetted channel. We found a statistically significant linear relationship between the surface-subsurface tracer flux (mgL-1min-1) and streambed hydraulic conductivity (cms-1). Our data also suggest that heterogeneity played an important role in controlling the tracer concentration in the wells. Based on our data, we conclude that hyporheic exchange in the streambed of the urbanized Indian Creek was controlled by a combination of hydraulic conductivity and heterogeneity.