Assessment of soil organisation and monitoring of soil water content using electrical resistivity tomography in the uplands of Lao PDR

Abstract : An Electrical Resistivity Tomography monitoring experiment was carried out in the uplands of Lao PDR in the Houay Pano experimental catchment. By comparing data obtained from the calculated cross section of electrical resistivity with hand auger observations, the detailed soil organisation in such a complex mountainous environment was characterised. By comparing the seasonal variation of ground electrical resistivity with the monitoring of groundwater level through a series of piezometer monitoring points, ground water fluxes along hillslopes can be measured precisely. Our study confirmed that stream water mainly corresponds to pre-event water stored in soils that is forced out by the infiltration of fresh rain water. The study also indicated that ground water recharge is larger for hillslopes with fallow vegetation than for cultivated hillslopes where soils are bare at the beginning of the rainy season suggesting the importance of surface cover on infiltration.