22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Exploring the use of Fiber Optic Distributed Temperature Sensing for monitoring seawater intrusion

23 Sep 2019, 15:45
15m
Conference room 1.A ()

Conference room 1.A

Oral Topic 5 - Tools, methods and models to study groundwater Parallel

Speaker

Mrs Laura del Val (Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya (UPC) - Associated Unit: Hydrogeology Group (UPC-CSIC))

Description

As pressure on coastal fresh groundwater resources increases, interest in coastal aquifers monitoring rises. The weakest point of coastal aquifers occurs at the fresh-salt water interface induced by seawater intrusion (SWI), highly sensible to any change in the heads of the fresh and salt water bodies. Therefore, the position, width and dynamics of the interface is one of the main features of a costal aquifer to be monitored and understood, in order to improve coastal groundwater management.
Traditionally, changes in electric conductivity have been used to identify and monitor the interface in coastal aquifers. Alternatively, natural differences in temperature between fresh and the saline groundwater bodies are also known to provide useful information. Recently, Fibre Optic Distributed Temperature Sensing (FO-DTS) is increasingly being used in the field of hydrogeology because of its high spatial and temporal resolution. To test the FO-DTS technology for the monitoring and quantification of the SWI dynamics, distributed temperature data were collected every 15 minutes in a Mediterranean granular aquifer, matching with the occurrence of an extreme rainfall event. Thermal response to the recharge event is compared to data collected independently in wells with electrical conductivity and temperature probes. A 2D variable density heat and solutes transport model is performed with CodeBright. The numerical model is used to confirm the conceptual model defined from the interpretation of the FO-DTS data, explore possible future scenarios and prove the usability of this technology for coastal aquifers monitoring.
Distributed temperature data reflect thermal responses to the extreme recharge event. However, smaller displacement of the interface, like those produced by tides, were not detected by FO-DTS. Only hydraulic processes with thermal responses larger than 0.15 ºC could be observed with this technology. Therefore, the high spatial and temporal resolution provided by FO-DTS is limited by its temperature resolution, which depends on many factors, such as the DTS sensor, the number of connections, the calibration baths and the calibration process. In any case, it is a promising technology for monitoring fast responses of the interface to large scale processes like recharge events.

Acknowledgements: This work was funded by the projects CGL2016-77122-C2-1-R/2-R of the Spanish Government. We would like to thank SIMMAR (Serveis Integrals de Manteniment del Maresme) and the Consell Comarcal del Maresme in the construction of the research site. We would like to acknowledge Sensornet (UK) for their support and collaboration in the acquisition and operation of their Oryx+ system.

Primary authors

Mrs Laura del Val (Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya (UPC) - Associated Unit: Hydrogeology Group (UPC-CSIC)) Prof. Maarten W. Saaltink (Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya (UPC) - Associated Unit: Hydrogeology Group (UPC-CSIC)) Dr Albert Folch (Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya (UPC) - Associated Unit: Hydrogeology Group (UPC-CSIC)) Dr Maria Pool (Institute of Environmental Assessment and Water Research (IDAEA), CSIC - Associated Unit: Hydrogeology Group (UPC-CSIC)) Prof. Jesus Carrera (Institute of Environmental Assessment and Water Research (IDAEA), CSIC - Associated Unit: Hydrogeology Group (UPC-CSIC)) Prof. Olivier Bour (Geosciences Rennes, UMR 6118 University Rennes 1 - CNRS) Prof. John S. Selker (Department of Biological and Ecological Engineering, Oregon State University)

Presentation Materials

There are no materials yet.
Your browser is out of date!

Update your browser to view this website correctly. Update my browser now

×