Investigation of groundwater potential aquifer using geophysical technique at Sawah Sempadan, Malaysia

Sufficient water supply is a vital process throughout the growth stages in all plants including paddy. Even though Malaysia has an annual rainfall around 2600 millimetres, which is above the global average, the distributions of rainfall are uneven which causes certain areas to face limited water supply. In addition to that, seasonal monsoons also affect the pattern of rainfall which leads to dry and wet season. Therefore, an alternative reliable resource of groundwater needs to be investigated with the aim of supplying water continuously over the years. Thus, identifying potential groundwater that can be extracted to irrigate the paddy field area is crucial. In this study, an approach of geophysical technique; 2D resistivity survey was applied. 2D resistivity survey was conducted to result a resistivity profile or familiarly called electrical resistivity tomography (ERT) which represents the subsurface media using RES2DINV software. Wenner-Schlumberger array and a layout of 5 metres electrode spacing for inner and 10 metres for outer cable were employed in all surveys of this study. The resistivity profiles of this study consist of three major lines and six minor lines. Each major line was formed from 7 surveys of 400 metres in length, which made up to 1.6 km after overlapping at 200 metres. SURFER software was used to create this major line resistivity profile. While minor line was made from a single survey of 400metre in length perpendicular to major lines at field. Using the ERT of major and minor lines, one can spot that there are few potential groundwater aquifer located throughout the profiles. Potential aquifer of resistivity profiles were identified based on comparison of geological log to resistivity survey made at that particular well location. The potential groundwater was acknowledged to be in the sand layer which ranges between 50 to 250 Ωm. There were five potential aquifer locations being pointed out at major lines and two at minor lines as on water quantity basis. The resistivity data with x-location of SURFER were later replaced by easting and northing data taken from the topography data using RTK GPS. A 3D skeleton model view of the groundwater potential aquifer at Block C Sawah Sempadan was created. This model shows the location of potential water aquifer spotted at the study area. The development of 3D model view of subsurface profile for selected field will act as reference for further study especially in developing wells in extracting groundwater that is needed to be supplied as irrigation water to the field