Patterns of Water, Heat, and Solute Flux through Streambeds around Small Dams

Abstract

Hyporheic exchange, enhanced by complex stream channel morphology, can influence biogeochemical processing in the streambed. These processes chemically alter water passing temporarily through the streambed, which eventually returns to the stream channel and can potentially affect surface water quality. To assess the degree of biogeochemical cycling induced by complex streambed morphology, we instrumented two 20-m reaches of Red Canyon Creek, Wyoming, each containing a small log dam, with in-stream minipiezometers and temperature data loggers. We simultaneously observed pore water geochemistry and streambed temperature dynamics in several bedforms located upstream or downstream of the dams. We modeled seepage flux into the streambed using heat transport modeling. Upstream of the dams, low-permeability sediments have settled out in low-velocity pools, and enhanced anaerobic biogeochemical cycling occurred in the streambed. Rapid flux into the streambed occurred in glides immediately above the dams, where streambed temperature dynamics and geochemistry were nearly identical to the stream. In riffle sequences downstream of the dams, the streambed was oxygen rich, showed evidence of nitrification, and temperature dynamics indicated high connectivity between the streambed and the stream. Further downstream, streambed pore water geochemistry indicated ground water discharge occurring at the pool-riffle transition. Assessing streambed biogeochemical cycling may be facilitated by coupling streambed temperature measurements with pore water geochemistry and can aid in understanding how hyporheic exchange contributes to overall stream biogeochemistry.

Spatial patterns of hyporheic exchange and biogeochemical cycling around cross‐vane restoration structures: Implications for stream restoration design

“…Boulton [2007], Boulton et al [2010], and Gooseff [2010, 2011] have emphasized the importance of the hyporheic zone in ecological restoration and called for a more complete approach to river restoration that includes hyporheic processes. However, postconstruction assessment of restoration projects is not widespread [Bernhardt et al, 2005[Bernhardt et al, , 2007Nagle, 2007], and few studies have investigated the impact of instream restoration structures on hyporheic exchange fluxes or water chemistry, with some notable exceptions Hill, 2006a, 2006b;Fanelli and Lautz, 2008;Kasahara and Hill, 2008;Lautz and Fanelli, 2008].…”

Changes in stream temperatures in response to restoration of groundwater discharge and solar heating in a culverted, urban stream

“…Streambed temperature measurements have been used to determine areas of maximum and minimum discharge within a stream reach (Conant, 2004), to develop a field-scale analytical solution for determining groundwater discharge rates (Schmidt et al, 2007), and to quantify groundwater flow in the vicinity of stream barriers, such as natural and constructed dams (Fanelli and Lautz, 2008). All of these studies describe the spatially heterogeneous role of groundwater discharge in stream-aquifer interactions.…”

Heat tracing to determine spatial patterns of hyporheic exchange across a river transect

“…Hyporheic exchange is substantially heterogeneous in most lakes, wetlands, streams, rivers, and estuaries, and many studies have addressed and quantified spatial heterogeneity of HEF, primarily to scale the flux measured on the order of square meters to a river reach, shoreline segment or an entire lake (Fanelli and Lautz 2008;Keery et al 2007;Kikuchi et al 2012;Sawyer et al 2012). In addition, the spatial heterogeneity of hyporheic exchange has been analyzed via numerical modeling (Cardenas 2009;Trauth et al 2013;Peyrard et al 2008).…”