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Open AccessArticle

High Resolution Monitoring of Seawater Intrusion in a Multi-Aquifer System-Implementation of a New Downhole Geophysical Tool

1
Hydrological Service, Jerusalem 36118, Israel
2
Department of Geography and Environment, Bar Ilan University, Ramat Gan 52900, Israel
3
ImaGeau, 34080 Montpellier, France
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Israel Oceanographic & Limnological Research, Haifa 3108000, Israel
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Geological Survey of Israel, Jerusalem 95501, Israel
6
Sede Boqer Campus, Ben-Gurion University, Beer Sheva 8499000, Israel
*
Author to whom correspondence should be addressed.
Water 2019, 11(9), 1877; https://doi.org/10.3390/w11091877
Received: 6 July 2019 / Revised: 23 August 2019 / Accepted: 23 August 2019 / Published: 9 September 2019
(This article belongs to the Special Issue Advances in Groundwater and Surface Water Monitoring and Management)
Monitoring of seawater intrusion is extremely important for the management of coastal aquifers, and therefore requires reliable and high-frequency monitoring tools. This paper describes the use of a new near field and downhole geophysical tool that monitors seawater intrusion in boreholes with high vertical resolution. This sensor is further used to study the impact of pumping on water electrical conductivity profiles (ECP) at the fresh-saline water interface. The new device was installed in a confined calcareous sandstone aquifer along the northern Israeli coast. The site includes two monitoring wells and one pumping well located at distances of 50, 75 and 125 m from shoreline, respectively. The new geophysical tool, called the subsurface monitoring device (SMD), was examined and compared to water an electric conductivity profiler (ECP) and a conductivity temperature depth (CTD) driver’s data. All methods show similar salinity trends, and changes in pumping regime were clearly identified with both the SMD and CTD. The advantage of using the SMD tool is the high temporal and spatial resolution measurement, which is transferred via internet and can be analyzed and interpreted in real time. Another advantage of the SMD is that it measures the electrical resistivity of the aquifer mostly outside the well, while both water ECP and the CTD measure in-well electrical conductivity; therefore, are subjected to the artefact of vertical flow in the well. Accordingly, while the CTD shows an immediate and sharp response when pumping is stopped, the SMD provides a gradual electric conductivity (EC) change, demonstrating that stability is reached just after a few days, which illustrates, more precisely, the hydrological response of the aquifer. View Full-Text
Keywords: seawater intrusion; high resolution monitoring; downhole geophysics; coastal aquifer; vertical flow in the well seawater intrusion; high resolution monitoring; downhole geophysics; coastal aquifer; vertical flow in the well
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MDPI and ACS Style

Tal, A.; Weinstein, Y.; Baïsset, M.; Golan, A.; Yechieli, Y. High Resolution Monitoring of Seawater Intrusion in a Multi-Aquifer System-Implementation of a New Downhole Geophysical Tool. Water 2019, 11, 1877.

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