Urban India is sucking groundwater at frightening rates

Bengaluru city, which has been in the news over the last few days for its growing water crisis, has been extracting groundwater at frightening rates. Despite the government’s campaign to ban new borewell drillings and a mandate to register existing borewells, the city continues to rely on its growing number of ~500,000 illegal wells, of which an unknown number are abandoned. This uncontrolled extraction has taken a toll on the water resources in the city and led to dry borewells as the rainfall has played truant and lakes have dried - leading to a scramble for water and increasing reliance on private water tankers, and forced the administration to resort to unsustainable methods such as getting water over long distances from the Cauvery to deal with the present crisis. 

Pune’s groundwater extraction is not small by any means too. The annual groundwater extraction in the city ranges from 32 to 71 percent as a proportion of the average annual rainfall of 770 mm. This range  is worrisome as natural recharge rates for the basalt aquifers in Pune city are a lesser as compared to the rainfall leading to the current trend of unsustainable extraction or an underestimation of the groundwater recharge to Pune’s aquifers.

Over 80 percent of the urban domestic water supply in India is met through groundwater. According to the national compilation of groundwater resources in the country– 2022, Bengaluru and Chennai are in an over-exploited stage, while Delhi, Hyderabad and Kolkata are in the critical stage of groundwater extraction with Pune and Ahmedabad being in a semi-critical state.

Most of the groundwater extracted in Chennai, Delhi and Hyderabad is for domestic purposes, while it is used for irrigation in Pune, Ahmedabad and Bengaluru irrigation with Pune breaking the limit. Delhi ranks the highest followed by Chennai, Pune and Hyderabad in domestic water use. 

Rural India too depends majorly on groundwater for irrigation

It is not only urban water, but more than 60 percent of irrigation requirements in rural India are met by groundwater. A recent study titled 'Half of twenty-first century global irrigation expansion has been in water-stressed regions' in Nature Water uses the latest subnational irrigation statistics from various official sources to develop a gridded global estimate of Area Equipped for Irrigation (AEI) for the years 2000, 2005, 2010 and 2015 examined global irrigation patterns finds that:

Area equipped for irrigation has been rising in India

Global AEI in the year 2015 was 329 Mha with Asia dominating, accounting for 222 Mha (68 percent) of the total AEI, followed by North America (37 Mha, 11 percent) and Europe (31 Mha, 9 percent). China (72 Mha), India (70 Mha) and the United States (28 Mha) alone accounted for more than half (52 percent) of the total global AEI. The countries in which irrigation expanded (on net) the most were China (12.8 Mha) and India (8.5 Mha).  A major reason behind this expansion was to maintain food self-sufficiency.

There are shifts in areas equipped for irrigation by locations

The study focused on finding out the extent to which these shifts have occurred in locations where water resources are relatively abundant and can potentially support additional blue water demand without depleting streamflow or aquifers (that is, sustainable expansion).

Water stress was defined as green water stress (GWS), when rainfall is insufficient to meet a crop’s water requirement and supplementary irrigation is needed, or blue water stress (BWS), when renewable surface and groundwater availability (that is, total availability after accounting for environmental flows) is insufficient to meet irrigation water demand. In the case of GWS, expansion of irrigation infrastructure can be a valuable strategy for buffering against variations in rainfall, provided that blue water resources are sufficiently available. In the case of BWS, expansion of irrigation infrastructure can lead to enhanced depletion of aquifers and streamflow.

India accounts for 36 percent of global unsustainable irrigation expansion

Globally, AEI has expanded by 11 percent since 2000. Of the countries with the largest AEI in 2015, India and Pakistan saw the most unsustainable expansion, with 86 percent (12.1 Mha) and 87 percent (1.53 Mha) of the gross expansion in AEI, respectively, taking place in locations that were already experiencing blue water stress (BWS).

The study found that more than half (52 percent) of the irrigation expansion has taken place in areas that were already water-stressed in the year 2000, with India alone accounting for 36 percent of global unsustainable expansion.

The study finds that while irrigation expansion is important to ensure food security, expansion in areas where water stress already exists can lead to further depletion of streamflow and aquifers in these locations. The paper warns that countries continuing to practise and expand irrigated agriculture in places where water is scarce are subjecting subject themselves to an increasing likelihood that freshwater resources could become inaccessible (that is, groundwater table drawdown and streamflow depletion) and ultimately impose physical and/or economic limits on the levels of irrigated production. 

What can be done to prevent future water crisis 

Thus, sustainable solutions are urgently needed to avoid or reverse unsustainable groundwater extraction practices in urban and rural India.

In urban areas 

A panel discussion on Bengaluru's water crisis organised on the 12th March 2024 by Citizen Matters highlighted that while efforts were being made at present to deal with the crisis by making water from the Cauvery available in the city, reusing the wastewater available to refill lakes, the following steps needed to be undertaken to deal with the crisis in the long term:

• Reviving the traditional water harvesting structures such as tanks in the city. 
• Undertaking steps to revive all the remaining lakes in the city
• Process and reuse all the wastewater generated in the cities to recharge lakes, water plants, clean cars, floors, cooling thermal power plants and at construction sites
• Make plans for rainwater harvesting by taking into consideration the terrain in urban Bangalore. Learn from efforts such as recharging shallow aquifers done by organisations such as the  ‘Million Wells for Bengaluru’ campaign undertaken by Biome Environmental Trust to map wells in the city and help in groundwater recharge.
• Ensure strict implementation of laws on rainwater harvesting
• Control on rampant constructions and concretisation in the city, strict enforcement of laws that prevent wastage of water by the residents and mainly the builder lobby.
• Reuse all the water generated from the RO plants
• Decentralisation of STPs for wastewater treatment and processing at the local level

Rural areas

• Using water resources efficiently through adoption of technologies such as precision agriculture and micro irrigation and preventing flood irrigation
• Rainwater harvesting and catching the rain where it falls
• Reviving traditional water harvesting methods and structures
• Collective water budgeting in villages through education, training, aquifer mapping exercises and participatory groundwater management
• Crop rotation and preventing cultivation of water thirsty crops in water scarce or groundwater critical areas.