Exploratory drilling is the most effective means of prospecting for locating and evaluating potential aquifers. It also facilitates demarcation of aquifer morphology and geometry. Aquifer performance test conducted in these bore holes/ tube wells help evaluate the aquifer parameters. Ground Water exploration in CGWB, NCCR is carried out to study and characterize the aquifers. The process of exploration involves selection of sites based on hydrogeological and geophysical investigations followed by drilling and pumping tests.

CGWB, NCCR, Raipur has 3 drilling rigs which include 1 rotary (WAB-69/31) and 2 combination rigs (SHM-86 and RECP-88/90)

Nearly 650 wells have been drilled by CGWB in the state of Chhattisgarh. The following figures show the location and yield (during drilling) of the wells.

Exploratory drilling in the state has lead to the following broad inferences

• Granitiods of Kanker and Bastar are found to be more productive as compared to those encountered in the northern part of the state. Dongargarh granites encountered in parts of Rajnandgaon district are moderately productive.

• Among the rock types of Chhattisgarh Super Group, the limestones are highly productive because of development of cavernous zones.

• The limestones of Indravati Group of Bastar district are also cavernous and are highly potential.

• Sandstones belonging to Chhattisgarh Super Group form good aquifers and are next to the limestones in ground water potential.

• Maniari Shales are highly potential due to development of fractures and secondary openings formed by leaching of gypsum.

• Shales other than Maniari Shales are the least productive among the rock types of Chhattisgarh Super Group and the yield in Gunderdehi Formations is quite low.

• The Gondwana formations are moderately productive and form potential aquifers down to depth of 250m on an average. In the Gondwana formations of Raigarh District, artesian conditions exist in and around Tamnar

• Besides the above rock formations the quaternary alluvium forms aquifers of limited aerial extent, which occur mostly along the major rivers. These aquifers are very high in ground water potential