Large Scale Mapping of Fractures and Groundwater Pathways in Crystalline Hardrock By AEM

Subash Chandra, Esben Auken, Pradip K. Maurya, Shakeel Ahmed, Saurabh K. Verma

Research output: Contribution to journalArticleResearchpeer-review

40 Citations (Scopus)

Abstract

In hardrocks that cover about 20% of the Earth’s surface, it is difficult to locate steady sources for groundwater due to inadequate understanding of the fracture networks. A comprehensive knowledge of fracture distribution at the regional scale is necessary to delineate sustainable aquifers and manage them efficiently. The resistivity maps derived from the airborne electromagnetic (AEM) survey over the Ankasandra watershed in Karnataka, India, reveal sharp and deep zones of low formation resistivity, which indicate groundwater-bearing zones. It is found that some of these zones are hydrogeologically connected through fracture networks resulting in augmented yield. AEM results in combination with an in-depth understanding of the geological structures successfully map these groundwater-saturated fracture networks (or hydrogeological lineaments) that we term as ‘Hydrolins’. As groundwater occurrence is generally associated with lineaments, we analyzed the drilling and geophysical logs from 21 wells within a 380 sq.km area to study the relationships of various lineaments with ‘Hydrolins’, particularly in respect of their groundwater potential. AEM results, though calibrated and correlated with a limited number of well data, revealed a threshold groundwater horizon (TGWH), found to be at 80 m depth for Ankasandra watershed, beyond which a strong correlation exists between the depth of a well and its yield. While the TGWH may differ for different watersheds, the approach presented here can be readily adopted to map sustainable groundwater sources in hardrocks worldwide.

Original languageEnglish
Article number398
Number of pages11
JournalScientific Reports
Volume9
Issue number1
DOIs
Publication statusPublished - 1 Dec 2019
Externally publishedYes

Programme Area

  • Programme Area 2: Water Resources

Fingerprint

Dive into the research topics of 'Large Scale Mapping of Fractures and Groundwater Pathways in Crystalline Hardrock By AEM'. Together they form a unique fingerprint.

Cite this