Groundwater needs a recharge

India has 4 per cent of global water resources for its use in spite of having 17 per cent of the world population. Its water resources are under immense pressure. There are wide spatial and temporal variations in the distribution of water. India’s per capita availability of water has touched the water stressed benchmark, and is likely to reach water scarce scenario by 2050.

As per hydrological cycle about 1,999 billion cubic meter (bcm) of water resources are annually generated and, of this, water which can be beneficially utilised is only 1,123 bcm. Of the available water resources, 433 bcm of water resources are from groundwater contributions and the remaining from surface water contributions. NITI Aayog Report (2019) reported that about 21 States will soon run out of groundwater resources.

Backbone of agriculture

Groundwater is the backbone of India’s agriculture and drinking water security. Contribution of groundwater in agriculture is about 62 per cent, 85 per cent in rural water supply and 50 per cent in urban water supply, respectively. Its availability is not uniform in space and time. India’s storage capacity is low compared to available resources.

The live storage capacity of dams in India is about 258 bcm. The reservoirs are unequally distributed as 70 per cent of India’s reservoir capacity is limited to Andhra Pradesh, Gujarat, Madhya Pradesh, Karnataka, Maharashtra and Odisha. On the other hand, Delhi, Haryana, Punjab and Rajasthan have only 5 per cent of reservoir storage capacity. This puts a high pressure on the utilisation of groundwater resources.

The impact of climate change on hydrological cycle is well known. Across the world, India is the second most flood prone country. Increased frequency of flooding causes enormous problems to the people. This also causes significant pressure on drainage system and sanitation management.

The main source of groundwater resources is rainfall which contributes to nearly 61 per cent of total annual groundwater recharge according to a Central Groundwater Board (CGWB) report ‘National Compilation on Dynamic Groundwater Resources of India, 2022’. Recharge of groundwater depends on the type of rock formation in a place. Type of rock formation and their storage and transmission characteristics have a significant influence on groundwater recharge. For example, porous formations (such as alluvial formation) in the Indo-Ganga-Brahmaputra basin have high specific yields and are good repositories of groundwater.

The assessment of CGWB (2022) shows that the total annual groundwater recharge is 437.60 bcm, and the annual extractable groundwater resources is 398.08 bcm. In addition, the total annual groundwater extraction has been assessed at 239.16 bcm. Thus, the average groundwater extraction for the country as a whole comes to 60.08 per cent. However, extraction of groundwater for various uses in different parts of the country is not the same.

Out of 7,089 ground water assessment units (CGWB 2022), 1,006 units (46.05 bcm) are ‘over exploited’ indicating that the groundwater extraction exceeds its annual replenishable groundwater recharge. There are 158 assessment units categorised as ‘saline’ as major part of groundwater in aquifers is ‘brackish’ or ‘saline’.

The encroachment among India’s 24,24,540 water bodies (Ministry of Jal Shakti 2023), mostly in rural areas, is a matter of concern as it reduces scope of groundwater recharge.

The CGWB Report (2022) showed that States such as Punjab, Rajasthan, Haryana, and Delhi are exploiting groundwater more than the quantity of its recharge. This overexploitation of groundwater is likely to be the source of geogenic contaminants such as arsenic and fluoride. A significant amount of groundwater is used by various States such as UP, Tamil Nadu, Punjab, Maharashtra, Rajasthan, MP, Haryana, Gujarat, etc. Although the rains are intense in many places, the rainwater harvesting is minimal. As a result groundwater recharge is also minimal out of monsoon rains. For example, in Delhi the potential of rainwater harvesting is 2500 million litres per day, but most of the rainwater goes waste.

The groundwater level can be increased by two means — artificial recharges and rainwater harvesting. Artificial recharge is a process that increases infiltration either through faster rates or due to availability of source water in a longer time duration. The source water can be rainwater which is harvested on the surface or from other sources such as canal or treated waste water. The natural recharge is a very slow process.

However, regions like Indus-Ganga-Brahmaputra plains have seen higher recharge rate mainly because of higher rainfall, better permeability, and better storage capacity of aquifers.

In artificial recharge, emphasis is not only on volumetric gain of water; also attention can be paid to quality issues.

Agenda for action

In the era of climate change, the water security should be addressed by policymakers and other stakeholders. Variability of surface water due to climate change should be recognised and addressed. One option is to manage groundwater and strengthen the same. Groundwater recharge programme should be given priority to address variability of surface water due to climate change.

Water regulators should be involved in sustainable management of groundwater. Special emphasis should be given to States such as UP, Delhi, Rajasthan, Punjab, and Haryana where groundwater extraction is not sustainable. There is a need for increasing the level of groundwater artificial recharge in the States.

A sustainable campaign for efficient groundwater management should be facilitated at all levels, various communities and concerned stakeholders. The Centre’s ‘Atal Jal Scheme’ as applicable to water stressed States for bringing up behavioural changes in groundwater management, should be extended to other States as well, and effectively implemented.

The writer is Distinguished Fellow, The Energy and Resources Institute (TERI) and former Secretary, Union Ministry of Water Resources

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