Dynamic Groundwater resources of India

Background

Ground Water Resources Assessment is carried out at periodical intervals jointly by State Ground Water Departments and Central Ground Water Board under the guidance of the respective State Level Committee on Ground Water Assessment at State Levels and under the overall supervision of the Central Level Expert Group. Such joint exercises have been taken up earlier in 1980, 1995, 2004, 2009, 2011, 2013, 2017, 2020 and 2022. The latest in this series is 2023.

Methodology of assessment

Ground water resource as in 2022 have been estimated following the guidelines mentioned in the Ground Water Estimation Committee (GEC) 2015 methodology using appropriate assumptions depending on data availability.

The assessment involves computation of dynamic ground water resources or Annual Extractable Ground Water Resource, Total Current Annual Ground Water Extraction (utilization) and the percentage of utilization with respect to annual extractable resources (stage of Ground Water Extraction). The assessment units (Talukas/blocks/mandals/firkas) are categorized based on Stage of Ground Water Extraction, which are then validated with long-term water level trends.

Source of replenishable ground water resources

The main source of replenishable ground water resources is recharge from rainfall, which contributes to nearly 61 % of the total annual ground water recharge. India receives about 119 cm. of rain annually on average, with high spatial variation. A major part of the country receives rainfall mainly during SW Monsoon season, spread over the months of June to September, except in Tamil Nadu, where the major contribution is from NE monsoon during the period October– December. There are also States such as Jammu and Kashmir, Himachal Pradesh and Uttarakhand which receive significant rainfall in all seasons.

Over 75% of the annual rainfall is received in the four rainy months for June to September only thereby leading to large variations on temporal scale. The average annual rainfall is 119 cm, but it has great spatial variations. The areas on Western Ghats, Sub-Himalyan areas in North East and Meghalaya Hills receive heavy rainfall over 250 cm annually, whereas the areas of Northern parts of Kashmir and Western Rajasthan receive rainfall less than 40 cm. A major part of the country including Northern, Central and Eastern parts receives annual normal rainfall between 75 and 150 cm. In general, rainfall decreases westwards in the northern part of the country, whereas it decreases eastwards and then increases toward the coast in Peninsular India.

Type of rock formations and their storage and transmission characteristics have a significant influence on ground water recharge. Porous formations such as the alluvial formations in the Indo- Ganga-Brahmaputra basin generally have high specific yields and are good repositories of ground water. Ground water occurrence in the fissured formations occupying nearly two-thirds of the geographical area of the country, on the other hand, is mostly limited to the weathered, jointed and fractured portions of the rocks.

Dynamic Ground Water Resources of India, 2023

As per the 2023 assessment report, the total annual ground water recharge for the entire country is 449.08 billion cubic meters (BCM), marking an increase of 11.48 BCM compared to the previous year (2022) and annual ground water extraction for the entire country is 241.34 BCM.  Further, out of the total 6553 assessment units in the country, 736 units have been categorized as ‘Over-exploited’.

• Assessment indicates increase in ground water recharge
• Analysis indicates improvement in ground water conditions in 226 assessment units in the country compared with 2022 assessment data
• Stage of ground water extraction stands at 59.23%.
• Out of total 6553 assessment units, 4793 units categorized as ‘Safe’

To access the complete report, click here.

Dynamic Ground Water Resources of India, 2022

As per the 2022 assessment report, the total annual ground water recharge for the entire country is 437.60 billion cubic meters (BCM) and annual ground water extraction for the entire country is 239.16 BCM.  Further, out of the total 7089 assessment units in the country, 1006 units have been categorized as ‘Over-exploited’.  The average stage of ground water extraction for the country as a whole works out to be about 60.08 %. 

The extraction of ground water for various uses in different parts of the country is not uniform. Out of the total 7089 aassessment units (Blocks/ Districts/ Mandals/ Talukas/Firkas) in the country,

• 1006 units in various States (14 %) have been categorized as ‘Over-Exploited’ indicating ground water extraction exceeding the annually replenishable ground water recharge.
• A total of 260 (4 %) assessment units have been categorized as ‘Critical’, where the stage of ground water extraction is between 90-100 % of annual extractable resources available.
• There are 885 ’Semi-Critical’ units (12 %), where the stage of ground water extraction is between 70 % and 90 % and
• 4780 (67 %) assessment units have been categorized as ‘Safe‘ where the stage of Ground water extraction is less than 70 %.

Apart from this, there are 158 assessment units (2 %), which have been categorized as ‘Saline’ as major part of the ground water in phreatic aquifers is brackish or saline.

Similarly out of  24.69 lakh sq km recharge worthy area of the country, 4.30 lakh sq km (17 %) are under ‘OverExploited’, 0.77 lakh sq km (3 %) are under ‘Critical’, 3.03 lakh sq km (12 %) are under ’Semi-Critical’,  16.18 lakh sq km ( 66 %) are under ‘Safe’ and 0.4 lakh sq km (2 %) are under ‘Saline’ category assessment units. Out of 398.08 bcm of Total Annual Extractable Resources of the country, 46.05 bcm (12 %) are under ‘Over-Exploited’, 13.02 bcm (3 %) are under ‘Critical’, 47 bcm (12 %) are under ’Semi-Critical’, 291.88 bcm (73 %) are under ‘Safe’ category assessment units.

In comparison to 2020 assessment, the total numbers of assessment units in the country have increased from 6965 to 7089 with major contribution (in increase) from the State of West Bengal, Karnataka,Rajasthan, Uttar Pradesh, Telangana, Gujarat and Jharkand. The total annual ground water recharge has increased from 436 to 437.6 bcm, where major increase is noticed in the States of Bihar, Telangana, Andhra Pradesh, Tamilnadu, Arunachal Pradesh, Odisha and Gujarat. The changes are attributed mainly to changes in recharge from ‘Other Sources’. Accordingly, the annual extractable resource of GW Resource Assessment, 2022 on comparison GW Resource Assessment, 2022 also shows a increase from 397.6 to 398.08 bcm. The ground water extraction has marginally decreased from 244.92 to 239.16 bcm. The overall stage of groundwater extraction has marginally decreased from 61.6 % to 60.08 %.

The over-exploited assessment units are mostly concentrated in :

• the north western part of the country including parts of Punjab, Haryana, Delhi and Western Uttar Pradesh where even though the replenishable resources are abundant, there have been indiscriminate withdrawals of ground water leading to over-exploitation;
• the western part of the country, particularly in parts of Rajasthan and Gujarat, where due to arid climate, groundwater recharge itself is limited, leading to stress on the resource and
• the southern part of peninsular India including parts of Karnataka, Tamil Nadu Telangana and Andhra Pradesh, where due to inherent characteristics of crystalline aquifers, the ground water availability is low.

In some areas of the country, good continuous rainfall and management practices like ground water augmentation and conservation measures through government and private initiatives have resulted in improvement in ground water situation. Ground water resources assessment, like other fields of science, requires continuous refinements.

To access the complete report, click here. 

Source : Central Ground Water Board, Department of Water Resources, River Development & Ganga Rejuvenation, Ministry of Jal Shakti, Government of India