Investigation of Hyporheic Flow Using a High Resolution Temperature Grid: Visualization and Simulation
Abstract
Groundwater- stream exchanges with a gaining stream in the western part of Denmark are currently investigated over different spatial scales; from the sediment-water interface (SWI) to catchment scales . Previous investigations at one of our sites, using heat as tracer (Jensen and Engesgaard, 2011), suggest that lateral/hyporheic flow is taking place at the SWI. Using heat as a tracer most often involves the assumption of 1D vertical flow in order to apply simple 1D analytical solutions to the heat transport equation. The purpose of this study is to investigate the suggested hyporheic/lateral flow across the SWI at the site using a high-resolution temperature grid to obtain a better understanding of the 3D heat distribution in the streambed. The grid consisted of 40 temperature probes, spaced approx. 1 m apart, each with 10 sensors unevenly distributed over 0.5 m. The grid was deployed in the stream bed from May to Sep 2010 covering a bank to bank area of 40 m2 (8 by 5 m). The 3D heat distribution varies considerably across the stream showing nearly constant groundwater temperatures (8 C) at all depths at the southern bank, while a greater variation in temperature is observed towards the northern bank (Fig. 1). The nearly constant temperatures over the entire depth at the southern bank could indicate a strong constant (regional) discharge and/or the influence of lateral flow. Frequent multi-level measurements of the hydraulic heads, slug-tests, and electrical resistivity tomography (ERT) have been carried out to develop a conceptual hydrogeological model of the wetland-stream continuum. On this basis, a preliminary flow model has been developed confirming that the southern boundary is likely subjected to lateral flow. Hence, 3D simulations of heat transport is currently under the development using HydroGeoSphere to analyze and understand the streambed heat distribution at the SWI.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.H33I..08K
- Keywords:
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- 1830 HYDROLOGY / Groundwater/surface water interaction