These data are described in Rickel, A., Hoagland, B., Navarre-Sitchler, A. and Singha, K. (2021). Seasonal shifts in surface water-groundwater connections from electrical resistivity in a ferricrete-impacted stream. Geophysics, v. 86, no. 5, 13 p. 10.1190/GEO-2020-0599.1.

The efficacy of the hyporheic zone (HZ) — where surface water and groundwater mix — for processing nutrients or uptake of metals is dependent on streambed hydraulic conductivity and stream discharge, among other characteristics. Here, we explore electrical resistivity tomography (ERT) of hyporheic exchange in Cement Creek near Silverton, Colorado, which is affected by ferricrete precipitation. To quantify flows through the HZ, we conducted four-hour salt injection tracer tests and collected time-lapse ERT of the streambed and banks of Cement Creek at high and low flow. We installed piezometers to conduct slug tests, which suggested a low permeability zone at 44-cm depth likely comprised of ferricrete that cemented cobbles together. Based on the ERT, the tracer released into the stream was constrained within the shallow streambed with little subsurface flow through the banks. Tracer was detected in the HZ for a longer time at high flow compared to low flow, suggesting that more flow paths were available to connect the stream to the HZ. Tracer was confined above the ferricrete layer during both the high- and low-flow tests. Mass transfer and storage area parameters were calculated from combined analysis of apparent bulk conductivity derived from ERT and numerical modeling of the tracer breakthrough curves. The hyporheic storage area estimated at low discharge (0.1 m2) was smaller than at high discharge (0.4 m2) and residence times were 2.7 h at low discharge and 4.1 h at high discharge. During high discharge, in-stream breakthrough curves displayed slower breakthrough and longer tails, which was consistent with the time-lapse electrical inversions and One-dimensional Transport with Inflow and Storage (OTIS) modeling. Our findings indicate that ferricrete reduces the hydraulic conductivity of the streambed and limits the areal extent of the HZ, which may lower the potential for pollutant attenuation from the metal-rich waters of Cement Creek.