A distributed heat transport experiment to estimate thermal conductivity of streambed sediments and quantify variability of groundwater/surface water interactions
Abstract
Characterization of groundwater/surface water interactions became a key element for the management of water quality and quantity since these exchanges partly control biogeochemical reactivity as well as the distribution and abundance of many freshwater species. However, their quantification is challenging since exchange processes vary both in time and space. Here, we present a new method based on an active distributed heat transport experiment within the streambed sediments allowing quantifying both the distribution of the thermal conductivity of sediments and the variability of groundwater/surface water interactions.
The experimental setup consists in deploying an armored fiber optic cable along the streambed within the sediments of a stream. The cable is heated electrically through its steel frame while the elevation in temperature is continuously monitored using fiber optic Distributed Temperature Sensing. The independent quantification of both thermal conductivity and fluxes along the cable is based on two analytical solutions, validated numerically with COMSOL Multiphysics and experimentally in a sand-box model. The experimental methodology has been applied in the Selune River, where 600 meters of cables have been installed in the streambed. This large flow-system is controlled by both upstream dam regulations and water abstraction in a surrounding aquifer. The application of the heat experiment confirmed the impact of pumping on flow direction and on flow velocities distribution into the streambed. From the spatially distributed method, we also highlighted the spatial co-evolution of thermal properties and water fluxes. Thus, we showed the importance of streambed structure in the control of groundwater/surface water exchanges and the relevance of using DTS to characterize the spatio-temporal complexity of exchanges in streams.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H41K1845S
- Keywords:
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- 0408 Benthic processes;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1829 Groundwater hydrology;
- HYDROLOGY