Electrical resistivity tomography and induced polarization study for groundwater exploration in the agricultural development areas of Brunei Darussalam

摘要

Electrical resistivity tomography and induced polarization studies were conducted for groundwater exploration in eight selected agricultural sites in Brunei Darussalam. The study was undertaken to meet the growing demands for water supply in the agricultural sector, particularly for paddy field irrigation purposes. This study conducted nineteen surveys with lengths of up to 800 m and a depth of investigation of up to 150 m below ground level. 2D inverted resistivity and chargeability models delineated subsurface geological formations and aquifer zones in the study area. Aquifer zones were detected in all the investigated sites, with resistivity values ranging from 1 to 100 ohm m and chargeability values ranging from 0 to 10 ms. Based on the resistivity and chargeability interpretations, two new groundwater wells were drilled and constructed in two of the investigated sites. Borehole drilling encountered aquifer zones primarily in sand and sandstone layers. Hydraulic tests of the newly drilled boreholes revealed groundwater yields of 4.3 and 288 m(3)/day. Transmissivity values of the aquifer units estimated using the Cooper-Jacob time-drawdown solutions are 0.53 and 109 m(2)/day, while their hydraulic conductivity values are 0.05 and 2.75 m/day, respectively. Our findings suggest weak to moderate groundwater yield for withdrawal and distribution for irrigation purposes in the investigated sites. The present study helped decision-makers take suitable measures for placing future groundwater irrigation wells and achieve significant groundwater exploration results in the study area and other areas with similar geological settings.