Estimation of hydraulic parameters in a hard rock aquifer using integrated surface geoelectrical method and pumping test data in southeast Guangdong, China

Abstract

Estimation of hydraulic parameters is important for the prediction of the future availability of groundwater reserves. Conventionally, pumping tests are conducted on boreholes to measure these parameters. However, such tests are costly and time consuming, and can only provide limited spatial information. An integrated approach of geophysical method and pumping tests is cost-effective and efficient alternative for the estimation of aquifer parameters. A geophysical method of vertical electrical sounding (VES) was carried out in Huizhou ADS site of China for the delineation of aquifer potential zones to assess the groundwater resources contained within the weathered rock. Initially, the pumping test data were used to determine the hydraulic parameters namely hydraulic conductivity (Kw) and transmissivity (Tw) for available production wells. Afterwards, one empirical relation between pumped hydraulic conductivity (Kw) and aquifer resistivity (ρa), and another between pumped transmissivity (Tw) and transverse resistance (Tr) were obtained to estimate hydraulic conductivity (K) and transmissivity (T) for all VES stations where pumping tests were not conducted. In this way, the entire study area was investigated to delineate the aquifer potential zones i.e., high potential aquifer zone with ρa 150 m2/day and K > 4 m/day, medium potential aquifer zone with ρa ranging from 100 to 150 Ωm, T from 100 to 150 m2/day and K from 3 to 4 m/day, poor potential aquifer zone with ρa from 150 to 300 Ωm, T from 50 to 100 m2/day and K from 2 to 3 m/day, and negligible potential aquifer zone with ρa > 300 Ωm, T < 50 m2/day and K < 2 m/day. This investigation also deciphers functional analogous relation of Ωa with K and Tr with T in Huizhou, China. Therefore, similar integrated approach can be used in any geological similar area where the aquifer properties are required for the management of groundwater reserves.