Using high‐resolution distributed temperature sensing to quantify spatial and temporal variability in vertical hyporheic flux

Abstract

[1] Hyporheic flow can be extremely variable in space and time, and our understanding of complicated flow systems, such as exchange around small dams, has generally been limited to reach-averaged parameters or discrete point measurements. Emerging techniques are starting to fill the void between these disparate scales, increasing the utility of hyporheic research. When ambient diurnal temperature patterns are collected at high spatial resolution across vertical profiles in the streambed, the data can be applied to one-dimensional conduction-advection-dispersion models to quantitatively describe the vertical component of hyporheic flux at the same high spatial resolution. We have built on recent work by constructing custom fiber-optic distributed temperature sensors with 0.014 m spatial resolution that are robust enough to be installed by hand into the streambed, maintain high signal strength, and permit several sensors to be run in series off a single distributed temperature sensing unit. Data were collected continuously for 1 month above two beaver dams in a Wyoming stream to determine the spatial and temporal nature of vertical flux induced by the dams. Flux was organized by streambed morphology with strong, variable gradients with depth indicating a transition to horizontal flow across a spectrum of hyporheic flow paths. Several profiles showed contrasting temporal trends as discharge decreased by 45%. The high-resolution thermal sensors, combined with powerful analytical techniques, allowed a distributed quantitative description of the morphology-driven hyporheic system not previously possible.

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

“…These flux rates across the streambed interface are important for ecosystem health because they represent the magnitude of the exchange of water and dissolved constituents between the channel and hyporheic zone. With increasing depth, vertical flux rates showed a tendency to decrease towards zero, and we attribute this pattern to penetration of the TP rods through shallow, curved hyporheic flow paths that become more horizontal with depth [similar to Briggs et al, 2012]. This pattern was most evident upstream and downstream of secondary riffles (Figures 3a and 3b), where shallow hyporheic flow paths are expected to start and end.…”

Active heat pulse sensing of 3D-flow fields in streambeds

“…It is also 25 widely used by other disciplines e.g. ecology where the thermal regime in river systems plays an important role in ecosystem health (Caissie, 2006;Harvey and Wagner, 2000;Brunke and Gonser, 1997;Boulton et al, 1998).…”

“…In addition, an assumption is made that the dominant exchange process is in the vertical direction only and the horizontal or lateral component of flow is considered to be negligible. There are very few investigations which have tried to capture both the vertical and horizontal component of flow, as the determination of the non-vertical component is challenging (Munz et al, 2016;Briggs et al, 2012;Shanafield et al, 2016). 5…”

Active heat pulse sensing of 3-D-flow fields in streambeds

“…1918 E. W. Banks et al: Active heat pulse sensing of 3-D-flow fields in streambeds tion only and the horizontal or lateral component of flow is considered to be negligible. There are very few investigations which have tried to capture both the vertical and horizontal component of flow, as the determination of the non-vertical component is challenging with the physical installation of sensors to measure the flow field as well as the mathematical framework to process the data (Munz et al, 2016;Briggs et al, 2012;Shanafield et al, 2016).…”

“…It is also widely used by other disciplines, e.g. ecology, where the thermal regime in river systems plays an important role in ecosystem health (Caissie, 2006;Harvey and Wagner, 2000;Brunke and Gonser, 1997;Boulton et al, 1998).…”