Quantitative guidance for efficient vertical flow measurements at the sediment–water interface using temperature–depth profiles

Abstract

Upward discharge to surface water bodies can be quantified using analytical models based on temperature-depth (T-z) profiles. The use of sediment T-z profiles is attractive as discharge estimates can be obtained using point-in-time data that are collected inexpensively and rapidly. Previous studies have identified that T-z methods can only be applied at times of the year when there is significant difference between the streambed-water interface and deeper sediment temperatures (e.g., winter and summer). However, surface water temperatures also vary diurnally, and the influence of these variations on discharge estimates from T-z methods is poorly understood.For this study, synthetic T-z profiles were generated numerically using measured streambed interface temperature data to assess the influence of diurnal temperature variations on discharge estimation and provide insight into the suitable application of T-z methods. Results show that the time of day of data collection can have a substantial influence on vertical flux estimates using T-z methods. For low groundwater discharge fluxes (e.g., 0.1 m d −1 ), daily transience in streambed temperatures led to relatively large errors in estimated flow magnitude and direction. For higher discharge fluxes (1.5 m d −1 ), the influence of transient streambed temperatures on discharge estimates was strongly reduced. Discharge estimates from point-in-time T-z profiles were most accurate when the uppermost point in the T-z profile was near the bed interface daily mean (two time periods daily). Where temperature time series data are available, daily averaged T-z profiles can produce accurate discharge estimates across a wide range of discharge rates. Seasonality in shallow groundwater temperature generally had a negligible influence on vertical flow estimates. These findings can be used to plan field campaigns and provide guidance on the optimal applicationof T-z methods to quantify vertical groundwater discharge to surface water bodies. K E Y W O R D Sanalytical solutions, gaining stream, groundwater discharge, groundwater, surface water exchange, heat as a groundwater tracer, hyporheic flow, river-aquifer interactions, streambed mapping

The Significance of Vertical and Lateral Groundwater–Surface Water Exchange Fluxes in Riverbeds and Riverbanks: Comparing 1D Analytical Flux Estimates with 3D Groundwater Modelling

“…Aside from conceptual and model structure limitations, uncertainty in vertical flux estimates can also arise from limitations regarding temperature sensor accuracy and placement [89] and measurement resolution [92]. The time of day when the temperature measurements are taken can also have an effect on flux estimates, as discussed by Irvine et al [75]. To overcome some of these limitations, active heat tracing techniques are being developed that allow for the injection of artificial heat pulses into the riverbed and the quantification of the resulting thermal plume in multiple directions [52,93,94] However, these techniques are more expensive and much more complex in data analysis.…”

“…Our measurements were performed in summer making a steady-state assumption appropriate. Diurnal temperature variations can also have an influence on vertical flux estimates [75]. However, the highfrequent diurnal temperature signal has a limited penetration depth in the riverbed.…”

A Distributed Temperature Profiling System for Vertically and Laterally Dense Acquisition of Soil and Snow Temperature

“…For example, temperature time-series have been used to explore the control that climate and subsurface properties have over permafrost dynamics (Brewer, 1958;Jorgenson et al, 2010), biogeochemical fluxes (Reichstein and Beer, 2008), plant function and root growth (Iversen et al, 2015), species and community distribution (Myers-Smith et al, 2011), and heat and water fluxes (Cable et al, 2014). Further, many studies have used temperature data to determine the vertical velocity of groundwater flow, surface-water-groundwater exchange, and groundwater recharge (Bredehoeft and Papaopulos, 1965;Briggs et al, 2014;Constantz, 2008;Hatch et al, 2006;Irvine et al, 2020;Racz et al, 2012). Time-series of temperature data have also been used in a parameter-estimation framework to quantify the soil thermal parameters and, in some cases, the fraction of soil constituents including organic matter content (Beardsmore et al, 2020;Nicolsky et al, 2009;Tabbagh et al, 2017;Tran et al, 2017;Zhu et al, 2019).…”

Estimating Hydrothermal Properties and High-Frequency Fluxes From Geophysical Measurements in the Hyporheic Zone

“…The propagation of daily river temperature signals in the hyporheic is particularly sensitive to flow variations because thermal properties are much less variable than hydraulic properties: thermal conductivity ranges between 1.5 and 6 W m −1 • C −1 for unconsolidated water saturated porous materials while hydraulic conductivity can vary over 6 orders of magnitude (e.g., Lapham, 1989;Constantz et al, 2002;Rivière et al, 2020). Various analytical and numerical methods based on the heat transfer equation have emerged (e.g., Stallman, 1965;Hatch et al, 2006;Rau et al, 2014;Irvine et al, 2020). Related software implementations are the VFLUX2 software using the steady state analytical solution (Gordon et al, 2012;Irvine et al, 2015b), the FAST program using the transient analytical solution (Kurylyk and Irvine, 2016), or the FLUX-BOT Matlab program using a numerical model for solving the advection-diffusion equation (Munz and Schmidt, 2017).…”