Comprehensive hydro-geophysical prospecting to delineate fresh water zone in the coastal aquifer, South India

摘要

The integrated hydrogeophysical surveys were used to discriminate between fresh and saline groundwater in the coastal aquifer zones of lower Vellar river basin, south India, which is considered to be the main source of groundwater in the basin. Geologically, the basin consists of tertiary and quaternary formation. In order to delineate the freshwater aquifer zone, sixty-nine (69) VES locations were surveyed by Schlumberger electrode arrangement and eight (8) scanning surveys were conducted by multi electrode scanning method. The VES results, reflect that the overall resistivity ranges from 0.01 to 12,670 Ωm and thickness varies from 0.49 to 49.9 m, with a maximum of four subsurface layers. The dominant curve types are H and QH followed by KH (8) and K (6). The pseudo sections prepared to understand the variations of subsurface characteristics and to delineate potential fresh/saline water aquifer zones in the basin. Whereas the scanning surveys results showed resistivity ranges from 1 to 500 Ωm. The resistivity 20-60 Ωm was considered as freshwater aquifer zone and observed at six locations at varying depths. The both the VES and scanning results were correlated with existing borewell lithology and it showed reliable matching. The results of this survey identified the freshwater aquifer zones (20-60 Ωm) in central and south-central part of the basin with high potential aquifer thickness and optimum yield. This integrated hydrogeophysical methods proved to be an excellent solution for delineation of fresh water aquifer zone and could be applied to any other basins with similar lithological conditions.