From streambed temperature measurements to spatial-temporal flux quantification: using the LPML method to study groundwater-surface water interaction

Abstract

Knowledge on groundwater–surface water interaction and especially on exchange fluxes between streams and aquifers is an important prerequisite for the study of transport and fate of contaminants and nutrients in the hyporheic zone. One possibility to quantify groundwater–surface water exchange fluxes is by using heat as an environmlental tracer. Modern field equipment including multilevel temperature sticks and the novel open‐source analysis tool LPML make this technique ever more attractive. The recently developed LPML method solves the one‐dimensional fluid flow and heat transport equation by combining a local polynomial method with a maximum likelihood estimator. In this study, we apply the LPML method on field data to quantify the spatial and temporal variability of vertical fluxes and their uncertainties from temperature–time series measured in a Belgian lowland stream. Over several months, temperature data were collected with multilevel temperature sticks at the streambed top and at six depths for a small stream section. Long‐term estimates show a range from gaining fluxes of −291 mm day−1 to loosing fluxes of 12 mm day−1; average seasonal fluxes ranged from −138 mm day−1 in winter to −16 mm day−1 in summer. With our analyses, we could determine a high spatial and temporal variability of vertical exchange fluxes for the investigated stream section. Such spatial and temporal variability should be taken into account in biogeochemical cycling of carbon, nutrients and metals and in fate analysis of contaminant plumes. In general, the stream section was gaining during most of the observation period. Two short‐term high stream stage events, seemingly caused by blockage of the stream outlet, led to a change in flow direction from gaining to losing conditions. We also found more discharge occurring at the outer stream bank than at the inner one indicating a local flow‐through system. With the conducted analyses, we were able to advance our understanding of the regional groundwater flow system. Copyright © 2015 John Wiley & Sons, Ltd.

Was That Assumption Necessary? Reconsidering Boundary Conditions for Analytical Solutions to Estimate Streambed Fluxes

“…Some recent works using multiple frequencies (e.g., Anibas et al, ; Hu et al, ; Schneidewind et al, ; Vandersteen et al, ; Wörman et al, ) use spectral power information (essentially amplitude information) from multiple frequencies to estimate parameters. The choice appears to be motivated by distrust of phase information (see for example comments in Schneidewind et al, ; Vandersteen et al, ).…”

LPMLE3: A novel 1‐D approach to study water flow in streambeds using heat as a tracer

“…Temperature‐time series were recorded at location ML6 in the Slootbeek (51°12′36.6″N 4°50′14.9″E), a small lowland stream of around 4 km length in North‐Eastern Belgium (Figure ) and tributary to the Aa River. The Slootbeek is fed by several drainage canals and its stream stage is heavily influenced by its location in an agricultural landscape [ Anibas et al ., ]. The streambed is composed predominantly of fine sand and silt with varying content of organic matter at the top and occasional gravel deposits.…”

“…Further details about the field site, the measurement setup and additional measurements can be found in Anibas et al . [].…”

A New Approach to Quantify Shallow Water Hydrologic Exchanges in a Large Regulated River Reach

“…This method is only applicable when there is constant upward flux. The second method is the Local Polynomial method with a Maximum Likelihood estimator (LPML) developed by Vandersteen et al [39] and has been extensively tested with time-series data [52]. The LPML model transforms temperature signals from the temporal domain to the frequency domain and finds the best vertical flux rate to fit equations that describe the subsurface signal frequency as a response function of the surface signal frequency.…”