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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Water Quality and Ecology Research » Research » Publications at this Location » Publication #184351
Title: HYPORHEIC AND TOTAL STORAGE EXCHANGE IN SMALL SAND-BED STREAMS

Author
item STOFLETH, J - UNIVERSITY OF MISSISSIPPI
item Shields Jr, Fletcher
item FOX, GAREY - UNIVERSITY OF MISSISSIPPI

Submitted to: American Society of Civil Engineers
Publication Type: Proceedings
Publication Acceptance Date: 5/15/2005
Publication Date: 8/1/2005
Citation: Stofleth, J.M., Shields, F.D., Jr., Fox, G.A. 2005. Hyporheic and Total Storage Exchange in Small Sand-Bed Streams. In R. Walton (ed.) Proceedings of the 2005 World Water and Environmental Resources Congress: Impacts of global climate change. American Society of Civil Engineers Proceedings 173(587), doi: 10.1061/40792(173)587, Reston, VA.

Interpretive Summary: Scientists have recently begun to understand that stream flow may be significantly delayed by “detours” through subsurface storage zones of shallow groundwater, but measurements of this phenomenon are mainly from steep streams with beds of boulders, cobble or gravel. Such “storage” of streamflow has major implications for contaminant trapping and processing. We conducted a series of measurements in two small, incised streams, one with a bed of sand and the other with a bed of sand and gravel, and the resulting data were used to compute a series of parameters that may be used to describe the interaction between surface flow and subsurface zones. Subsurface flow had an insignificant impact on surface flow, but the presence of flow obstructions like beaver dams greatly increased the amount of time it took for water to pass through the stream reaches we studied. These results highlight basic differences between coarse-bedded mountain streams and those more typical of agricultural landscapes, and will be useful to scientists studying such streams.

Technical Abstract: Nutrient processing and carbon storage in stream ecosystems are linked to hydraulic retention. Hydraulic retention refers to the departure of stream flow from ideal “plug flow,” and reflects fluid movement through surface and hyporheic storage zones. Most existing information about hyporheic exchange is based on flume studies or field measurements in relatively steep streams with beds coarser than sand. Continuously injected tracers (brine) were used to measure hydraulic retention in short reaches of two small, sand-bed streams with varying amounts of large wood and grain size distributions. Tracer curves were fit to the one-dimensional transport with inflow storage (OTIS-P) model, which output parameters describing hydraulic retention for comparison with work by others. Networks of minipiezometers were used to measure hydraulic gradients, which were used to compute hyporheic exchange. Parameters describing total retention were in the upper 50% of previously published values, but hyporheic exchange was only 0.01% to 0.49% of total exchange. Retention did not respond to differences in median bed material size, but increased with flow obstruction. Hyporheic storage was an insignificant component of total hydraulic retention in the small sand-bed streams studied.