ERT INVESTIGATION OF A BURIED WATER RESERVOIR

In order to prevent land deterioration, when searching for buried objects with imprecise location, non-invasive and non-destructive geophysical methods can be applied. The success of these methods depends on the target dimensions, its properties in certain induced or natural physical fields and thei...

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Bibliographic Details
Published inInternational Multidisciplinary Scientific GeoConference SGEM Vol. 1; no. 3; pp. 839 - 846
Main Authors Adrian, Serban, Florina, Eng Chitea, Dumitru, Ioane
Format Conference Proceeding
LanguageEnglish
Published Sofia Surveying Geology & Mining Ecology Management (SGEM) 01.01.2015
Subjects
Aquifers
Area
Arrays
Buried structures
Data interpretation
Data processing
Design
Dipoles
Electric currents
Electrical conductivity
Electrical resistivity
Electrodes
Geology
Geophysical exploration
Geophysical methods
Geophysics
Groundwater
Investigations
Nondestructive testing
pH effects
Rain
Rain water
Refilling
Reservoirs
Salinity
Tomography
Tubes
Water analysis
Water reservoirs
Water sampling
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Summary:In order to prevent land deterioration, when searching for buried objects with imprecise location, non-invasive and non-destructive geophysical methods can be applied. The success of these methods depends on the target dimensions, its properties in certain induced or natural physical fields and their contrast with the surrounding material, as well on the measurements profiles design. Such a test was executed for a buried water reservoir formed by two unequal wells with the maximum height of 3m. Each column was built up by concrete tubes having a diameter of 1.2m. Geophysical measurements, consisting in apparent electrical resistivity measurements, were executed using a multielectrode system. Several Electrical Resistivity (ERT) profiles, with different orientations, were delineated in order to intersect the area where the buried water reservoir was suspected to be located. ERT measurements were performed using Schlumberger, Wenner or Dipole-Dipole arrays, positioning the electrodes at an equidistance of 1m each. Two ERT profiles were previously executed in an undisturbed area in order to understand the local shallow geology illustrated by resistivity variations. ERT sections depicted an electrical layered structure formed by 3 distinct layers till the investigated depth of 7m. Despite the fact that the groundwater is often classified as electrically conductive, samples of water collected from the studied area showed low electrical conductivity properties. Due to the unexpected values obtained from the water collected during the geophysical measurements (32uS/em, at a pH of 6.868) from a nearby spring, a new water probe was analyzed after 3 months of the completion of geophysical campaign. The results showed a small change, the electrical conductivity of the water taken from the reservoir being 30 puS/cm, at a pH of 6.673, 0.0 salinity and TDS of 23ppm). The high electrical resistivity value of the phreatic aquifer from the studied location is a consequence of its refilling mainly by the raining water (electrical conductivity of mountain rain water collected from the study location was 20 uS/cm at a pH of 6.759 and TDS of 10ppm). Despite the challenging environment and unexpected low conductance of the groundwater, by means of ERT data interpretation the buried water reservoir was successfully located.
ISSN:1314-2704