India is suffering "the worst water crisis in its history", according to a report by government policy think tank NITI Aayog. Worsening water shortages - for farmers, households and industry - threaten the lives and incomes of hundreds of millions of Indians, and the economic growth of the country, the report said.
An estimated 163 million people out of India's population of 1.3 billion - or more than one in 10 - lack access to clean water close to their home, according to a 2018 report by WaterAid, an international water charity.
Chennai needs 800 million litres of water a day to meet demand for water, according to official data. At the moment, the government can provide only 675 million litres, according to the Chennai Metropolitan Water Supply and Sewerage Board. Chennai plugs that gap by buying water, encouraging residents to dig backyard borewells, or using private wells. In particular, Chennai depends on more than 4,000 private water tankers for its everyday water needs. Each tanker makes up to five trips a day, ferrying water. The government also runs a "dial a tanker" service to meet demand. Altogether, the tankers deliver 200 million litres of water a day to Chennai.
"There are neighbourhoods that depend on tankers throughout the year with no access to government water pipelines," said Shekhar Raghavan, director of the charity Rain Centre, which encourages rainwater harvesting and water conservation in urban areas. That, he said, has "given rise to the water mafia, which has total control over who will get how much water in the city".
Some residents say they are being held to ransom by private water distributors, as they have no option but to pay and no prospect of being hooked to government-run water supplies soon.
"We are totally dependent on water lorries and they are taking advantage of that fact," said Raman Duraiswamy, convener of the Sholinganallur constituency welfare association, an umbrella body that has 600 resident associations as members.
Tankers identify good groundwater sources in agricultural areas in neighbouring districts, pay a small fee to access the water and then sell if for 50 times that cost, Raghavan said. But what Raghavan called "indiscriminate" - and in many cases unauthorised - extraction of groundwater is creating growing problems as supplies run short. The firms' use of rural water is depriving people in those areas of sufficient water - and that fast-depleting water supplies mean it's time to rethink how water is managed in Chennai.
Last month, the Madras High Court - Chennai's highest court - finally ruled on a petition brought by 75 drinking water bottlers against the 2014 Tamil Nadu water restrictions.
Those restrictions cut off the companies' access to groundwater in areas identified as "critical" and "dark zones", where the water table is overused or very low. Bottlers had demanded exemption from the order, arguing that good monsoon rains would adequately replenish disappearing groundwater.
The court found otherwise. In its decision, judges called groundwater the "backbone of India's drinking water and irrigation system" and ruled that companies extracting it for profit without permission were engaged in criminal "theft".
Overuse of rural groundwater was threatening food production and the country's food security, the court ruled.
"The water crisis is worsening and even we are worried about depleting ground water," admitted Shakespeare Arulanandam, founder of the greater Tamil Nadu packaged drinking water manufacturers association, whose members filed the high court suit.
"In the future we can only pray more fervently and hope for good rains to ensure there is enough water to go around. It will be up to the Gods," he said.