Heli-Borne Survey to assess groundwater resources of Indian cities

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The Union Minister for Jal Shakti, Gajendra Singh Shekhawat along with Minister of State (Independent Charge) Science & Technology; Minister of State (Independent Charge) Earth Sciences; Dr. Jitendra Singh inaugurated the Heli-Borne Survey for Groundwater Management in Arid Regions today at Jodhpur, Rajasthan.

https://twitter.com/MoJSDoWRRDGR/status/1445275108415787010?s=20
Under the Aquifer Mapping Programme, the Central Ground Water Board, Ministry of Jal Shakti, and CSIR-NGRI (National Geophysical Research Institute), Hyderabad, have signed an agreement for the use of advanced heli-borne geophysical surveys and other scientific studies in parts of Rajasthan, Gujarat, Haryana, Punjab, and Himachal Pradesh covering an area of 3.88 lac sq. km.

What does the survey aim for?

The Heli-Borne Survey aims to conduct high-resolution aquifer mapping using heliborne geophysical studies, including the identification of artificial recharge sites, 3D geophysical models, Geophysical Thematic maps in horizontal and vertical planes, Aquifer Geometry of the principal aquifer with demarcation of de-saturated and saturated aquifers, and Aquifer System with relatively fresh and saline zones.

The survey also intends to map the spatial and depth-wise distribution of any paleochannel networks that may exist, as well as their connection to the aquifer system. The predicted outcome includes selecting suitable areas for groundwater withdrawal and water conservation through artificial or regulated aquifer recharge.

Last year work for Phase 1 was approved for 1.01 million square kilometres at a cost of Rs 45.8 crore including GST. A Memorandum of Understanding was signed, and the first instalment of 4.58 cr was released in March 2021. Phase 1 is expected to be completed within a year of the first payment being released, or by March 2022. Phase 2 will encompass 2.87 million square kilometres.

States covered:
Rajasthan – Total area to be covered is 66,810 sq.km out of which Priority area will be 16738 sq.km in Sikar, Jaisalmer & Jodhpur Districts & Normal area will be 50,072 sq.km in Ganganagar, Pali, Bikaner, Churu & Jalore Districts.

Haryana – Priority will be 2642 Sq.km in Yamunanagar and Kurukshetra Districts.

Gujarat – Priority will be 31907 Sq.km (Normal) in Jamnagar, Morbi, Rajkot, Surndra nagar & Devbhumi Dwarka Districts.

Advantages of Heliborne geophysical survey

The Heliborne geophysical survey has several advantages, including its speed, high data density, precision, and low cost. Furthermore, it can be carried out in both remote and inaccessible locations. The Heliborne Transient Electromagnetic Method (HTEM) is the greatest alternative for mapping the subsurface because it can efficiently map the subsurface conductivity fluctuations associated with groundwater.

How does it work?

The HTEM technology works by energising the ground system by sending a current pulse through the transmitter loop towed beneath the helicopter. The pulse causes eddy currents in the subsurface geological conductors, which produce secondary EM fields that are detected by a receiver loop located either in the centre or around the transmitter loop. After that, the data is evaluated, processed, and modelled to provide depth pictures that depict subsurface resistivity & conductivity distributions.

Ground-based measurements such as ground geophysics and borehole data are used to calibrate and evaluate the resistivity models, which leads to the construction of geological structures that control the occurrence of groundwater.