APPLICATION OF ELECTRICAL RESISTIVITY METHOD COMBINED WITH TIME DOMAIN ELECTROMAGNETIC DATA FOR CONCEPTUAL HYDROGEOLOGICAL MODELING IN CHANGWAT KAMPHAENGPHET

Abstract

Kamphaengphet is a part of upper Chao Phraya basin of Thailand. The rapid growth of agriculture results in significantly growing water demand. Reliance on surface water only causes water shortage. Groundwater resources are great alternatives to satisfy such a growing water demand, which solves the water shortage in dry season efficiency. Especially in the study area has groundwater stored in consolidated rocks that are difficult investigated. The popular methodology for groundwater survey is electrical geophysical technique. The vertical electrical sounding technique lacks data continuity. Later, the exploration has been relying on the multi–electrode system, resulting in accurate surveys and continuity resistivity data. Combining airborne time – domain electromagnetic data with electrical resistivity data will help investigate aquifers characteristics and pinpoint drilling well location accurately. Most of the study area overlain by residual soils and some area has already been changed to laterite that are underlain by shallow Silurian – Devonian phyllite which has resistivity higher than 200 ohm-meters. The study area shows significant weak zones in Silurian - Devonian rocks aquifers that are weathered phyllite. The fractures or fault zone is aligned in northern-southern directions. The weak zone has resistivity range from 10 to 50 ohm-meters which is the primary aquifer of the study area. This zone has high groundwater potential and groundwater well can be developed. Primary groundwater regional flow is from the northern high mountain to southern basin direction. The flow pattern in this consolidated aquifers is controlled by fractures or faults in rock formation.