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

Extracting water from fractures is a major problem in many parts of the world. Beside an often low yield it is hard to locate the fractures and predict if they contain water or not. Based on AEM application for aquifer mapping in India, a robust and cost effective way of locating fractures is described using airborne electromagnetic (SkyTEM) data in combination with magnetic and geological information. This paper introduces the following new concepts:
1) Precise mapping of water bearing FRACTURE NETWORKS in granitic hardrocks employing information derived from depth of investigation (DOI) obtained from AEM surveys.
2) HYDROLIN that defines underground lineaments controlled by water-saturated fracture network.
3) TGWH(critical depth called threshold groundwater horizon) bellow which probability of water saturated fracture network of regional extension increases significantly. This information is critical to establish sustainable groundwater resources and identify optimal regions to build recharge structures.
4) EXPONENTIAL DECAY pattern of fractures with depth in granite is established.
5) Relative GROUNDWATER POTENTIALITY of Hydrolin, Maglin (magnetically derived lineaments), Satlin (satellite derived lineaments) and Minlin (Mineralogically derived lineaments).

For details kindly go through full paper published in Nature: Scientific Reports | (2019) 9:398 | DOI:10.1038/s41598-018-36153-1
The paper can be downloaded using this link https://www.nature.com/articles/s41598-018-36153-1 external link (feel free to contact: schandra75@gmail.com for a copy if the link does not work)
 

Figure 1

Figure 1. (a) Hydrolin and Minlin constructed using DOI contours at 100 m depth, (b) Normalized percentage coverage of DOI patches with depth and model curve fitting the DOI coverage data.