As South India grapples with drought and water shortage, more tube wells are being dug. The existing ones are getting deeper as ground water levels fall – at least, this is the condition in Kerala, Andhra Pradesh, Karnataka and Tamil Nadu. What causes ground water levels to plummet? Is it pumping for irrigation of unsustainably high water-consuming crops, electricity subsidies or just poor rains? A new study by scientists from IIT Gandhinagar says that changing rainfall patterns and sea surface temperature in Indian ocean are likely to be most responsible.
The main player is the Indian Ocean’s surface temperature. If it gets warmer than normal, then South India gets rains and north central India experiences a drought, according to the study’s lead author, Vimal Mishra. These rainfall changes are a bigger driver of change in groundwater storage than the rampant pumping of groundwater for agriculture, he added.
However, the study asks us not to dismiss the problem of lowering water tables as being unfixable. “This suggests that we need to use groundwater resources more carefully and efforts should be put to enhance groundwater recharge,” Mishra told The Wire.
The study, titled ‘Relative contribution of monsoon precipitation and pumping to changes in groundwater storage India’, was published in the journal Nature Geoscience earlier this month. It analysed ground water extraction, storage and rainfall data for ten years gathered from various sources – including observation wells, satellites the NASA Gravity Recovery and Climate Experiment (GRACE) and from the Central Ground Water Authority.
Replacing millets with rice
It has found that groundwater withdrawals in the country have increased over tenfold in six decades, from 10-20 cubic kilometres per year in 1950 to 240-260 cubic kilometres per year in 2009. Measurements have also shown major declines in groundwater storage in some parts of the country, particularly in northern India, where it fell 2 cm a year between 2002 and 2013.
According to the study, the monsoons in North India, from June to September, have declined in intensity and duration since 1950, leading to more frequent and intense droughts. This, in turn, likely contributes to enhancing the abstraction and/or reduced recharge of groundwater. “Long-term drought can affect groundwater storage anywhere in India,” according to Mishra. “Long-term declining trends in rainfall are more prominent in northern India, [over the] Indo-Gangetic Plain, than southern India.”
“In northern India, groundwater recharge is a slow process and it may take years to get effective recharge through rainfall. Therefore, both efforts to improve water use efficiency in agriculture and enhancing groundwater recharge are required.”.
His coauthor Yoshide Wada is a deputy director at the International Institute for Applied Systems Analysis, Austria. And according to Wada, a warming climate may affect rainfall patterns but the storage and use of groundwater is in human hands. “If withdrawals of groundwater exceed storage the consequences would be disastrous,” he said in a statement released with the report. India relies heavily on groundwater for irrigation, particularly in the dry northern regions.
In many rainfall-scarce areas, groundwater has been exploited to plant water-guzzling crops like paddy and sugarcane, especially in areas like Vidarbha, Maharashtra, and Rayalaseema, Andhra Pradesh.
For example, in Chittoor district of Andhra Pradesh, a failed monsoon this year hasn’t managed to discourage farmers from planting sugarcane and paddy – rather than the millets they traditionally grew, leading to large-scale water pumping. A state government survey of tube wells in the area reported 1.7 lakh of them five years ago. According to P. Chennaiah, a farmer and a social worker, they have increased by over 30,000 now.
“We are not getting water even at 1,200 feet now,” he said, blaming the change in food cropping and consumption patterns for the situation. “We used to grow and eat millets, but now rice has become the staple diet thanks to the public distribution system.” Chennaiah runs seed banks for millets in a few blocks in Chittoor. He is also the head of the state’s Vyavasaya Vrittidarulu Union, affiliated with the National Alliance of People’s Movement led by Medha Patkar.
“I myself started growing millets two years ago and people saw that I got a good crop even in a drought year while all other crops failed. Now, many farmers are growing them, taking seeds from our seed bank.” For Chennaiah, the Green Revolution and the hybrid three-month paddy introduced by it was a disaster. “Earlier people ate rice only for festivals and very few grew them as it took six months.”
Solutions in water management
According to the IIT study, while 65% of the groundwater extracted in northwestern India happened thanks to a paucity of rainfall, the rest of it is attributable to choice of crops, intensive agriculture, subsidised electricity and market-driven prices. In south India, 64% of variability in groundwater storage was decided by rain fall; in north-central India, 30%. Other factors contributed to the rest of the pumping.
While these are mere numbers, and rainfall is beyond human control, geologists monitoring groundwater have said that though depletion rates do relate to the climate, no one is looking at solutions in water management. According to R.H. Sawkar, the secretary of the Geological Society of India: “What we are pumping is fossil water, water that accumulated millions of years ago. It will take many years for that to be replaced. So urgent steps for recharge are needed and these are missing.’’
Referring to the study, Sawkar said that the Sahyadri, or the section of the Western Ghats across Maharashtra and Karnataka, receives three-fourths of all the rainfall due peninsular India. “However, no one knows how much flows into the sea. It should be diverted and stored. It would help the entire region,” he said, while dismissing the idea of river-linking projects. “Let us link basins, sub-basins and micro-basins of the same river and not Ganga with Kaveri. This will help rivers stay alive or, in geological time, many of these rivers will be gone.”
Meanwhile, the IIT Gandhinagar scientists suggest shoring up groundwater resources, using better water management techniques and safeguarding our food and water securities in the process.