The World Resources Institute, a US based research organisation projected that the demand for water in India will grow to almost 1500 billion cubic m by 2030, driven by domestic demand for rice, wheat, and sugar (Tien Shiao et al., 2015, ‘3 Maps explain India’s growing water risks’, World Resources Institute). Against this, India’s current water supply is approximately 740 billion cubic m (bcm) (‘Charting our water future—Economic framework to inform decision-making,’ 2030, Water Resources Group, 2009). Thus, most of India’s river basins could face a severe deficit by 2030 unless concerted action is taken, with some of the most populous regions—the Ganga, the Krishna, and the Indus, facing the biggest absolute gap.
Groundwater resources are the only means of succour, given this scenario. But can our groundwater resources be relied upon? India’s groundwater resources are depleting in both quality and quantity, as per data made available by the Central Ground Water Board. The depletion can be perhaps partially ascribed to erratic monsoon trends and unavailability of necessary moisture for groundwater replenishment. However, water guzzling crops and cultivating a wrong combination of foodgrains can play a key role in depletion. According to a 2009 commentary by Matthew Rodell et al.,‘Satellite based estimates of groundwater depletion in India’, published in Nature, groundwater extraction during 2002 to 2008 was equivalent to a net loss of 109 cubic km of water in Rajasthan, Punjab and Haryana (including Delhi). The quantum of extraction was found to be double the capacity of India’s largest surface water reservoir. The data was calculated on the basis of terrestrial water storage change observations collected by the NASA Gravity Recovery and Climate Experiment (GRACE) satellites and simulated soil-water variations from a data-integrating hydrological modelling system related to groundwater depletion. During this period annual rainfall was close to normal and terrestrial water storage components (soil moisture, surface waters, snow, glaciers and biomass) did not significantly reflect a decline in total water levels. This would suggest that unsustainable consumption of groundwater for irrigation and other anthropogenic uses were likely to be the cause. The researchers concluded that if proactive measures are not taken to ensure sustainable groundwater usage, residents of the region maybe faced with a reduction of agricultural output and shortages of potable water.
Over exploitation of groundwater in South Asia has been extensively discussed in the report ‘Water and development, 1997-2007’ of the Independent Evaluation Group (IEG) of the World Bank, along with the problem of inadequate environmental flow and contamination. According to the report, “groundwater depletion is most severe in the Middle East, North Africa, and South Asia”. The IEG Report had stressed on monitoring groundwater quality, improving of landfill sites, and the reduction of infiltration by contaminated surface water into groundwater as measures to maintain the quality of precious aquifers.
Scientist S Suresh, in his paper, ‘Groundwater flow modelling in coastal aquifers of Southern part of Chennai Metropolitan Area, Tamil Nadu’ published in CGWB’s Bhujal News (January-December 2012), has noted with apprehension the mining of water in southern parts of Chennai by private entrepreneurs. Rainwater harvesting is a common practice by concerned residents; however, the erratic, sparse rainfall in the region has left Chennai severely water stressed and bereft of options. The water demand was 1026 million litres per day (mld) in 2001 and would become 1980 mld in 2021, while supply is expected to be around 1586 mld, if full capacity of the reservoirs and the groundwater supply are to be projected (ibid.). Owing to ballooning of urban populations, groundwater extraction levels are found to be far in excess of the recharging rates. However, in coastal areas, this has resulted in salinity ingress, as in Minjur, north of Chennai.
Conserving groundwater, saving aquifers
The quantity and quality of groundwater needs to conserved at several levels. One needs to:
- Limit groundwater extraction;
- Recharge existing aquifers; and,
- Prevent contamination of aquifers through salinity ingress, untreated sewage or industrial pollutants.
The demands of growing urban populations can certainly stress groundwater resources. Since it is impractical to stop groundwater extraction, we need to opt for methods to limit extraction. Rainwater harvesting and recharging models can be a good solution in regions of moderate to heavy rainfall. For other parts of the country faced with deficient rain, rainwater harvesting may not be enough. Recycling of available water must necessarily be opted for, to keep groundwater extraction to a minimum.
In rural regions, where agriculture accounts for large quantities of groundwater extraction, planting crops most suited to soil quality and topography can limit the over exploitation of water resources. Instead of rice or wheat, millets can be opted for in semi-arid, arid or upland regions. Similarly, in coastal regions faced with standing water, and salinity, planting trees like eucalyptus can solve the problem, and make the soil suitable for planting crops all year round. The system of rice intensification (SRI) or system of wheat intensification (SWI) methods can also reduce the consumption of water, and improve yields.
Rural areas are faced with contamination of water resources due to leaching of chemicals from fertilisers. Organic farming, which is fast catching on as a cheaper and healthier method to produce food can provide a good alternative to toxicity in groundwater. Contamination also occurs due to inadequate sanitation facilities, and the reckless release of untreated sewage and pollutants. Untreated industrial pollutants can not only destroy the soil, but introduce dangerous contaminants like cadmium into the food cycle. In areas with high groundwater levels, as in the deltaic regions of Bengal, it is safer to opt for ecological sanitation to prevent the contamination of the groundwater. In parts of the lower Gangetic basin, as also the deltaic region, arsenic and fluoride contamination of groundwater resources is common. This is generally brought about by overexploitation and continuous extraction of groundwater by growing populations.
In 2014, a collaborative study by CGWB and the Indian Institute of Remote Sensing to assess the impact of ground water abstraction on land subsidence in Northern India, was launched. The study involves application of state of art technologies such as space borne geodetic observations on land subsidence, predictive modelling, inter-comparison of land subsidence, ground water depletion and space based gravity anomaly. Deliverables include land subsidence information for selected cities of northern India and regional groundwater depletion scenario along with recharge assessment. Notwithstanding the bleak state of affairs, several water saving agricultural practices are already in place to ensure India’s agricultural productivity. These include “utilisation of the best available germplasm or other seed development, optimising fertiliser use, and application of crop stress management, including both improved practices (such as integrated pest management) and innovative crop protection technologies”, as noted by the 2030 Water Resources Group. India, it notes, only needs to undertake the ‘last mile’ completion of its canal projects and rehabilitation of its existing irrigation districts. It should hence, not prove too difficult to save our aquifers for posterity.