Context: Nearly one-sixth of India’s 6965 groundwater assessment units (block/tehsil/taluka) are ‘over-exploited, a  new findings of the Central Ground Water Board (CGWB) in a report released recently which is yet to be published.
Key highlights

• Nearly one-sixth of India’s 6965 groundwater assessment units (block/tehsil/taluka) are ‘over-exploited.
• This account for 35% of total assessed units along with two other categories of concern– ‘critical’ and ‘semi-critical’.
• Though depletion of groundwater continues due to indiscriminate extraction in several states/UT, the latest assessment of ‘dynamic groundwater resources’ in the country shows signs of improvement due to increased recharge and water use efficiency in 2020 compared to 2017.
• Numbers of ‘over-exploited’ and ‘critical’ assessment units have declined while the number of ‘safe’ units has increased compared to the previous assessment done three years ago.

Categories

‘Over-exploited’ units: Groundwater extraction substantially exceeds (more than 100%) the annually replenishable groundwater recharge.

• Between 90-100%: 'critical'
• Between 70-90%: 'semi-critical'
• Less than 70%: ‘safe’

Key points

• 1,114 out of 6,965 assessment units in the country are overexploited; 270 are critical; 1,057 are semi-critical; 4,427 are safe and 97 are saline.
• The findings show a percentage decline in numbers of ‘overexploited’ and ‘critical’ units — the first two categories of major concerns.
• Net availability of extractable ground water resources has increased from around 393 billion cubic meter (BCM) in 2017 to nearly 398 BCM in 2020.
• Extraction for all uses declined from 249 BCM to 245 BCM – it means more water remains as a natural reserve.
• Overall annual recharge was also increased during the period -- from 431.86 BCM in 2017 to 436.15 BCM in 2020.
• The findings show that the over-exploited areas are mostly concentrated in the north-western part of the country including parts of Punjab, Haryana, Delhi and western Uttar Pradesh.
• Even though the replenishable resources are abundant, there have been indiscriminate withdrawals of groundwater leading to over-exploitation.
• The other such areas include parts of Rajasthan and Gujarat, and southern part of peninsular India including parts of Karnataka, Andhra Pradesh, Telangana and Tamil Nadu.

Geophysical condition

• Parts of Gujarat and Rajasthan fall in arid climatic zone where recharge itself is limited, leading to stress on the resource.
• The groundwater availability is low in parts of peninsular India mainly due to inherent properties of crystalline aquifers.

Improved situation

• CGWB has recently attributed the improvement in groundwater situation to increase in natural and artificial (rainwater harvesting) recharge and decrease in extraction.

Decrease in extraction was mainly due to increased availability of surface water resources due to:

• Three consecutive years of normal monsoon rainfall
• Improved water use efficiency in different sectors