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New geophysical techniques for determining quantity and quality of ground water: an exemple from the Vientiane basin, Laos
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
2008 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

The access to clean drinking water in the rural Laos is often restricted. This, together with a poor hygiene, results in serious health problems. In a drilling program for water only around 30% of the boreholes carried water usable for drinking (JICA, 2000). The reason for the poor water quality was often a high content of salt. The aim of this study is to define water bearing geological formation and to test the possibility of using geophysical techniques to determine the quality of the groundwater in the Vientiane basin, Laos. This we do by the use of a combination of Magnetic Resonance Sounding (MRS), Vertical Electrical Sounding (VES) and water quality data gathered from wells in different geological environments. The MRS gives a direct image of the vertical distribution of water content and the electrical measurements are sensitive to the conductivity/quality of the water.The investigation area is part of the Khorat Plateau where rock salt is naturally occurring as shallow as 50 m in depth (Long et al., 1986), which inevitable affects the water quality in some deep wells. The results of the study show that MRS and VES measurements are effective in locating formations carrying fresh water as well as the salt bearing formation. Aquifers are identified in 19 of the 32 sites of measurements. The aquifers are related to specific geological formations and most often located at depths of 20 to 30 m and with water contents varying between 4 to 16 %. The decay times of the MRS signal suggests these aquifers to be predominantly composed of medium grained sand to gravel. The salt bearing formation is usually related to clay or mudstone, with low water contents and high VES  conductivity and can usually be found all over the basin at depths beneath 30 to 50 m.The electrical conductivity (EC) of water samples collected from shallow and deep wells correlates with the conductivities determined with VES and a fairly good correlation can be seen between EC, total dissolved solids (TDS), chloride and hardness. Layers of water with high quality, medium conductivity, are identified at specific depths and in restricted areas. The results demonstrate geophysics to be effective tools for localizing high quality groundwater and the results are important for guiding future drilling.

Place, publisher, year, edition, pages
2008.
National Category
Geophysics
Research subject
Applied Geophysics
Identifiers
URN: urn:nbn:se:ltu:diva-39775Local ID: ea612e70-b0cb-11dd-9c9d-000ea68e967bOAI: oai:DiVA.org:ltu-39775DiVA, id: diva2:1013293
Conference
Meeting Global Challenges in Research Cooperation : 27/05/2008 - 29/05/2008
Note
Godkänd; 2008; 20081112 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved

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http://www.csduppsala.uu.se/sidaconference08/

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Perttu, NilsElming, Sten-åke

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