India doesn’t have a problem of water scarcity, it suffers from overexploitation of groundwater; opportunity lies in supplementing resources by natural and artificial recharge
By Abhaya Agrawal
India receives an annual precipitation of 1,100-1,200 mm, which accounts for a total volume of 4,000 billion cubic metres (BCM), including snowfall. But only 1,123 BCM is estimated as average annual utilisable water. Of this utilisable water, 60% is surface water. According to the Central Ground Water Board (CGWB), total water utilisation in India is projected to be 1,447 BCM in 2050, against the utilisable quantum of 1,123 BCM. Thus, the demand will outstrip availability between 2030 and 2040.
India is the largest extractor of groundwater; it extracts nearly 25% of the world’s groundwater, according to UNESCO. The NITI Aayog has declared that 21 cities, including Delhi, Chennai and Bengaluru, are expected to run out of groundwater by 2020. Currently, India is extracting, on average, 62% of groundwater from its active recharge zone, of which almost 90% is for irrigation purposes. However, this average figure is highly deceptive. We have regions where water exploitation is more than 200%, making the situation critical.
Intensive exploitation of groundwater has severe consequences. If continuous extraction of groundwater exceeds the total replenishable rate, it leads to land subsidence, salt water intrusion, and becomes technically and financially non-feasible for stable water supply. Moreover, India suffers from geogenic pollution (elements naturally present in the geology) of arsenic, fluoride, iron and nitrate. Over-utilisation of groundwater has a cascading effect on the water quality, creating a higher concentration of these elements in the groundwater reservoir.
Most of the Indian riverine system is rain-fed, and due to large-scale removal of the green cover, the retention capacity has decreased tremendously. This has led to the major part of the precipitation into run-off, leading to flash floods in many parts of the country. In addition, due to decreased retention capacity, the natural capacity of groundwater recharge has also reduced. Decreased natural groundwater recharge capacity, coupled with overexploitation of groundwater, has led to a decrease in the baseflow (part of the groundwater that flows into the river) to the rivers in the non-monsoon period, due to which many rivers either run with the decreased flow or run dry.
Due to the increasing pressure on the development of groundwater resources, it has become the need of the hour to supplement these depleting resources. The natural recharge to the groundwater reservoir is restricted to a period of only 10 to 100 days, and is not adequate to keep up with the current rate of exploitation. Since a large volume of the precipitation flows out into the sea or gets evaporated, artificial recharge has been encouraged to supplement the natural recharge.
Artificial recharge is the process by which the groundwater reservoir is augmented through increased infiltration by using artificial structures. It could be understood in two ways—direct and indirect. In the direct method, contact area and residence time of surface water over the soil are increased to augment the groundwater, which can be achieved by either surface or subsurface techniques. Surface techniques include recharge basins, percolation tanks, contour bunding, etc. Subsurface techniques include injection wells, gravity head recharge well, recharge pits, recharge shafts. In the indirect method, rather than direct supply of water into aquifers, indirect methods are involved for recharging like induced recharge, bore blasting, hydrofracturing.
Mexico, by the Nation’s Waters law of 1992, declared water as a national property and it became obligatory for all consumers to legitimise their rights through procurement of water leases. Big industrial and commercial water users were quick to apply for a lease. However, the real challenge was registering water rights of agricultural users, who withdraw 80% of the total groundwater and keep track on their extraction. If Mexico, with 0.09 million wells, found it difficult to enforce the law, we can imagine the situation in India (19 million wells) if we also declare groundwater a government property. Currently, only in the notified area by the CGWB, the construction of wells is restricted, but can still be used for domestic use.
The government must encourage saving in consumption as well as rainwater harvesting through twin measures of pricing water on its economic cost and suitably rewarding bulk users (industry, farmers) through discounted tariff upon achieving measurable groundwater recharge.
India doesn’t have a problem of water scarcity; it suffers from variation in the scale of time and location of the precipitation. Rainwater harvesting, coupled with increased green cover (the government has proposed to increase the green cover of the country to 33% of the total area), is the ideal solution for the current water crisis because it can buffer out the spatial and temporal variation in the precipitation. Also, natural filtration by the geology of the Earth leads to better quality of water. Rainwater harvesting not only helps in replenishing the groundwater for future use, but also provides water for local use without transfer costs—this has social and environmental benefits. The study of our scriptures reveals that ancient thinkers such as Sarasvati and Manu, with a scientific bent, were also interested in exploring the means of storing rainwater.
The waters of sky,
the waters of rivers,
and water in the well,
whose source is the ocean,
may all these sacred waters protect me.
(The author is partner, Infrastructure & PPP, GPS, EY India. Anshul Tyagi contributed to the article.)