Airborne electromagnetic studies carried out in the granitic terrain of Tumkur district, Karnataka led to the introduction of new concepts such as (i) precise mapping of water bearing fracture networks using the information of depth of investigation (DOI); (ii) HYDROLIN that defines underground lineaments consisting of water-saturated fracture networks (iii) TGWH (critical depth called threshold groundwater horizon) below which probability of water saturated fracture networks of regional extension increases significantly.

The results obtained from the airborne electromagnetic (AEM) studies carried out in the granitic terrain of Tumkur district, Karnataka were helpful in establishing a methodology to map the fracture network and pathways vital for groundwater potential. This study paved way for introducing new concepts such as (i) precise mapping of water bearing fracture networks in granitic hard rocks using the information of depth of investigation (DOI) obtained from AEM surveys; (ii) HYDROLIN that defines underground lineaments consisting of water-saturated fracture network (Fig. 2.1a); (iii) TGWH (Threshold Ground Water Horizon), a critical depth below which the probability of water saturated fracture network of regional extension increases significantly