Targeting of high quality groundwater in the province of Vientiane, Laos, PDR

Magnetic Resonance Soundings (MRS) has been proven to be an efficient tool for detecting groundwater in the northern part of Vientiane, Laos PDR. This is the first time of testing in Laos’s area where the magnitude of earth magnetic field is higher than 43,700 nT. Testing of MRS here would have the advantages of high penetration depth and amplitude of MRS signals produced by the hydrogen proton in the subsurface water layers. Good signals have been achieved by carefully selecting sites of low background noise (< 1,000 nv), low magnetic susceptibility of subsurface and /or surface soil (< 10-3 si), and small variation of a local earth magnetic field. the mrs results agree well with the subsurface geological structures and the water productivity provided by boreholes data in the vicinity of investigated area. the higher water productivity was found in the area of thicker soft sediment layer. schlumberger ves has been conducted in the same target area of groundwater exploration and their results were also served for mrs inversion. comparison results of ves and mrs have been made and they are generally consistent. at the site where a water-bearing layer in the deeper parts is suggested by mrs with a detection of low signal amplitude and large variation of observed decay time, the ves result also confirmed that the layer is very high conductive. this case-study demonstrates that the mrs and ves methods can be an effectively selective method for groundwater investigation and can be integrated with other geophysical methods to fulfill groundwater database in laos pdr.Validerat; 20101217 (root