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TEM investigation on Challapampa aquifer, Oruro Bolivia

Larsson, Måns LU (2016) In Dissertations in Geology at Lund University GEOR02 20162
Department of Geology
Abstract (Swedish)
I denna studie utfördes en TEM (transient elektromagnetisk) undersökning på den Bolivianska altiplanon, norr om staden Oruro. I Oruro finns det ett underskott av dricksvatten och deras huvudsakliga vattenförsörjning kommer från aquiferen Challapampa. Målet med undersökningen var att kartlägga djup till bottnen på aqviferen, topografin av botten samt, om möjligt, akvitarder innom akviferen. De omkringliggande berget består av sandsten, skiffer och intrusioner. Ovanpå berget finns det Kvartära avlagringar som innehåller de största grundvattenreserverna. I det omkringliggande berget sträcker sig strukturer från nordväst till sydöst, och det är förväntat att strukturer med samma trend ska återfinnas på botten av akvifären, men även strukturer... (More)
I denna studie utfördes en TEM (transient elektromagnetisk) undersökning på den Bolivianska altiplanon, norr om staden Oruro. I Oruro finns det ett underskott av dricksvatten och deras huvudsakliga vattenförsörjning kommer från aquiferen Challapampa. Målet med undersökningen var att kartlägga djup till bottnen på aqviferen, topografin av botten samt, om möjligt, akvitarder innom akviferen. De omkringliggande berget består av sandsten, skiffer och intrusioner. Ovanpå berget finns det Kvartära avlagringar som innehåller de största grundvattenreserverna. I det omkringliggande berget sträcker sig strukturer från nordväst till sydöst, och det är förväntat att strukturer med samma trend ska återfinnas på botten av akvifären, men även strukturer kopplade till de intrusioner som finns.
TEM metoden är en transient elektromagnetisk sonderings metod som använder elektromagnetiska vågor för att undersöka marken. Ett magnetisktfält skapas när elektrisitet leds genom en kabel på marken. När strömmen stängs av induceras en elektromotorisk kraft ner i marken som inducerar virvelströmmar i lager med avvikande elektrisk ledningsförmåga. Virvelströmmarna skapar i sin tur ett sekundärt magnetfält som inducerar ström i mottagarspolen. Det sekundära magnetfältet varierar med markens elektriska ledningsförmåga och innehåller på så sätt information om markens fysiska egenskaper.
TEM metoden var väl lämpad för att undersöka hydrogeologiska egenskaper i en sand- och grus-dominerad avlagring. Ett större undersökningsdjup än väntat uppnåddes på 850 m under markytan i flera mätpunkter. Två lågresistiva dalar, som sträcker sig i en nordväst till sydöstlig riktning, hittades. Dalarna är tolkade att innehålla vattenmättade sediment. Djupet till berggrund i undersökningsområdets, absolut västra samt östra delar, är tolkat att vara cirka 75 m under markytan, medans djupet till berg i de tolkade dalarna är ca 130 m under markytan i den östra dalen och 120 m under markytan i den västra dalen. (Less)
Abstract
In this study a TEM (transient electromagnetic) investigation where preformed on the Bolivian altiplano north of the city Oruro. There is a deficit of drinking water in Oruro and the aquifer Challapampa is their main source of water. With this investigation the objective was to map the bottom limitation of the Challapampa aquifer and, if possible, restraining structures within the aquifer, aquitards. The surrounding bedrock consists mainly of sandstones and shale’s that has been penetrated by intrusions in several locations. Quaternary sediments on top of the bedrock hold most of the groundwater in the area. The general structures in the bedrock surrounding the Quaternary sedi-ments are in a northwest to southeast direction and similar... (More)
In this study a TEM (transient electromagnetic) investigation where preformed on the Bolivian altiplano north of the city Oruro. There is a deficit of drinking water in Oruro and the aquifer Challapampa is their main source of water. With this investigation the objective was to map the bottom limitation of the Challapampa aquifer and, if possible, restraining structures within the aquifer, aquitards. The surrounding bedrock consists mainly of sandstones and shale’s that has been penetrated by intrusions in several locations. Quaternary sediments on top of the bedrock hold most of the groundwater in the area. The general structures in the bedrock surrounding the Quaternary sedi-ments are in a northwest to southeast direction and similar structures are expected to be found underneath the sedi-ments.
The method used in this investigation was TEM, which uses transient electromagnetic (EM) waves to penetrate the ground. TEM is a geophysical technique that creates a magnetic field by passing an electrical current through an ungrounded cable. When the current is cut off, as quickly as possible, the magnetic field induces a current in its surrounding ground that results in a secondary magnetic field. The secondary magnetic field induces a current in the receiver antenna and electrical potentials are measured and registered in the instrument. The variation of the secondary magnetic field depends on the ground properties.
The TEM method is well suited for investigating groundwater properties in sand- and gravel-dominated deposits. A depth of investigation (DOI) to 850 m b.s. (meters below surface) was achieved in several points, which is over expectations. Two low resistivity valleys were found and interpreted as water saturated sedimentary valleys, where extend in a northwest to southeast direction over the studied area. The depth to the bedrock is interpreted to be around 75 m b.s., both in the western and eastern part of the area. The basal boundary for the interpreted sedimen-tary valleys crossing profile 3 (NorthH2, Fig. 24) is around 130 m b.s. for the eastern valley and 120 m b.s. for the western valley. (Less)
Popular Abstract
In this study a TEM (transient electromagnetic) investigation where preformed on the Bolivian altiplano north of the city Oruro. There is a deficit of drinking water in Oruro and the aquifer Challapampa is their main source of water. With this investigation the objective was to map the bottom limitation of the Challapampa aquifer and, if possible, restraining structures within the aquifer, aquitards. The surrounding bedrock consists mainly of sandstones and shale’s that has been penetrated by intrusions in several locations. Quaternary sediments on top of the bedrock hold most of the groundwater in the area. The general structures in the bedrock surrounding the Quaternary sedi-ments are in a northwest to southeast direction and similar... (More)
In this study a TEM (transient electromagnetic) investigation where preformed on the Bolivian altiplano north of the city Oruro. There is a deficit of drinking water in Oruro and the aquifer Challapampa is their main source of water. With this investigation the objective was to map the bottom limitation of the Challapampa aquifer and, if possible, restraining structures within the aquifer, aquitards. The surrounding bedrock consists mainly of sandstones and shale’s that has been penetrated by intrusions in several locations. Quaternary sediments on top of the bedrock hold most of the groundwater in the area. The general structures in the bedrock surrounding the Quaternary sedi-ments are in a northwest to southeast direction and similar structures are expected to be found underneath the sedi-ments.
The method used in this investigation was TEM, which uses transient electromagnetic (EM) waves to penetrate the ground. TEM is a geophysical technique that creates a magnetic field by passing an electrical current through an ungrounded cable. When the current is cut off, as quickly as possible, the magnetic field induces a current in its surrounding ground that results in a secondary magnetic field. The secondary magnetic field induces a current in the receiver antenna and electrical potentials are measured and registered in the instrument. The variation of the secondary magnetic field depends on the ground properties.
The TEM method is well suited for investigating groundwater properties in sand- and gravel-dominated deposits. A depth of investigation (DOI) to 850 m b.s. (meters below surface) was achieved in several points, which is over expectations. Two low resistivity valleys were found and interpreted as water saturated sedimentary valleys, where extend in a northwest to southeast direction over the studied area. The depth to the bedrock is interpreted to be around 75 m b.s., both in the western and eastern part of the area. The basal boundary for the interpreted sedimen-tary valleys crossing profile 3 (NorthH2, Fig. 24) is around 130 m b.s. for the eastern valley and 120 m b.s. for the western valley. (Less)
Please use this url to cite or link to this publication:
author
Larsson, Måns LU
supervisor
organization
course
GEOR02 20162
year
type
H2 - Master's Degree (Two Years)
subject
keywords
kartering, survey geofysik, sedimentologi, geology, hydrogeology, geophysics, sedimentary, geologi, hydrogeologi
publication/series
Dissertations in Geology at Lund University
report number
494
funder
SIDA, Minor Field Study programme (MFS)
language
English
id
8898403
date added to LUP
2017-01-10 16:03:42
date last changed
2017-01-31 10:51:53
@misc{8898403,
  abstract     = {In this study a TEM (transient electromagnetic) investigation where preformed on the Bolivian altiplano north of the city Oruro. There is a deficit of drinking water in Oruro and the aquifer Challapampa is their main source of water. With this investigation the objective was to map the bottom limitation of the Challapampa aquifer and, if possible, restraining structures within the aquifer, aquitards. The surrounding bedrock consists mainly of sandstones and shale’s that has been penetrated by intrusions in several locations. Quaternary sediments on top of the bedrock hold most of the groundwater in the area. The general structures in the bedrock surrounding the Quaternary sedi-ments are in a northwest to southeast direction and similar structures are expected to be found underneath the sedi-ments.
The method used in this investigation was TEM, which uses transient electromagnetic (EM) waves to penetrate the ground. TEM is a geophysical technique that creates a magnetic field by passing an electrical current through an ungrounded cable. When the current is cut off, as quickly as possible, the magnetic field induces a current in its surrounding ground that results in a secondary magnetic field. The secondary magnetic field induces a current in the receiver antenna and electrical potentials are measured and registered in the instrument. The variation of the secondary magnetic field depends on the ground properties.
The TEM method is well suited for investigating groundwater properties in sand- and gravel-dominated deposits. A depth of investigation (DOI) to 850 m b.s. (meters below surface) was achieved in several points, which is over expectations. Two low resistivity valleys were found and interpreted as water saturated sedimentary valleys, where extend in a northwest to southeast direction over the studied area. The depth to the bedrock is interpreted to be around 75 m b.s., both in the western and eastern part of the area. The basal boundary for the interpreted sedimen-tary valleys crossing profile 3 (NorthH2, Fig. 24) is around 130 m b.s. for the eastern valley and 120 m b.s. for the western valley.},
  author       = {Larsson, Måns},
  keyword      = {kartering,survey geofysik,sedimentologi,geology,hydrogeology,geophysics,sedimentary,geologi,hydrogeologi},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {TEM investigation on Challapampa aquifer, Oruro Bolivia},
  year         = {2016},
}