Automated monitoring of coastal aquifers with electrical resistivity tomography

Abstract

An Automated time-Lapse Electrical Resistivity Tomography (ALERT) system has been developed for the long-term monitoring of coastal aquifers. This ALERT system has been permanently installed in the River Andarax, Almeria, Spain to monitor and manage the impact of climatic change and landuse practice on the underlying Quaternary aquifer. An electrode array, nearly 1.6 km long, has been buried below the normally dry river bed with electrode take-outs at regular intervals of 10 m. The maximum depth of investigation is about 160 m below ground level. An unmanned, permanent control station, in a secure location, allows the aquifer to be interrogated remotely from the BGS office in the UK. Volumetric geoelectric images of the subsurface can be obtained "on demand" or at regular intervals; thereby eliminating the need for expensive repeat surveys. The entire process from data capture to image on the office PC is fully automated and seamless. The ALERT technology can provide early warning of potential threats to vulnerable water systems such as over-exploitation, rising sea levels, anthropogenic pollutants and seawater intrusion. The electrical images obtained (in space and time) are interpreted in terms of the hydrogeologic features including the seawater-freshwater interface. The timely detection and imaging of groundwater changes can help to regulate pumping and irrigation schemes.

Time-lapse resistivity investigation of salinity changes at an ex-promontory land: a case study of Carey Island, Selangor, Malaysia

“…Image analysis, from spatially distributed resistances at specific time intervals, is through timelapse electrical-resistivity tomography (TLERT). TLERT's various applications have attracted many researchers: Barker and Moore (1998) for physical-model tests of groundwater flow and contamination; Kemna et al (2002), Cassiani et al (2006), and Oldenborger et al (2007) for tracertest study of aquifers; Olofsson and Lundmark (2009) for impact monitoring of roadside-soil de-icing-salt in saltwater investigation; and Ogilvy et al (2009) for study of near-coast saltwater intrusion; in each, TLERT images relate change in salinity to transport of solutes.…”

“…TLERT is capable of minimal-invasionmonitoring of hydraulic processes in porous media by capturing temporal conductivity variations (Ogilvy et al 2009). TLERT measurements fill, less expensively, gaps in data on space between sets of boreholes (Maillet et al 2005).…”

High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer

“…As resistivity depends on properties such as saturation, solute concentration and temperature, timelapse ERT can be used to monitor natural and anthropogenic processes that cause changes in these properties, such as infiltration (Daily et al, 1992;Looms et al, 2008), saline intrusion (Slater and Sandberg, 2000;Ogilvy et al, 2007;, leachate recirculation (Guerin et al, 2004), and contaminated land remediation (Daily and Ramirez, 1995;LaBrecque et al, 1996;Slater and Binley, 2003;Halihan et al, 2005.…”

Geophysical-Geotechnical Sensor Networks for Landslide Monitoring

“…Monitoring at the site is based around the ALERT (Automated time-Lapse Electrical Resistivity Tomography) survey concept Ogilvy et al, 2009;Wilkinson et al, 2010a). The ALERT system provides the full capability for remote measurement, storage and transmission of geoelectrical data.…”