Indian workers carry water collected from what's left in the Puzhal reservoir, on the outskirts of Chennai, June 20, 2019. Getty

New Delhi -- Millions of people in the South Indian city of Chennai, the country's sixth largest metropolis, are facing an acute water shortage as the main reservoirs have dried up after a poor monsoon season. Some schools in the city have cut working hours and dozens of hotels and some restaurants have reportedly shut down due to the shortage.

The city of more than 4.5 million has been left to rely on wells and water brought in by truck. Thousands of wells dug across the city are leading to a rapid drop in the ground water level, and raising even further the concerns of environmentalists.

New wells are being dug as deep as 1,000 feet. Much of the water they produce isn't even fit to drink.

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"We have been facing this for the past two months," Aditya Manoharan, a student in Chennai, told CBS News. "The bore well water is so dirty that it's yellow in color. We can't drink it."

Price gouging

The well water can be used for washing, but residents have to buy bottled drinking water, and not everyone can afford it.

In parts of the city that don't have wells, water has been supplied by government trucks. Long lines of people waiting with buckets to collect from the trucks have become a common sight.

But the government trucks are only able to meet part of the demand, leaving the rest of the population at the mercy of private vendors, who appear to be making a killing off the crisis. A private truck carrying about 3,200 gallons of water would have cost around 1,500 Rupees (about $22) in April. Now such a delivery is going for about $85.

A man uses a hand-pump to fill up a container with drinking water as others wait in a queue on a street in Chennai, India, June 17, 2019. REUTERS

Reghu Ram, a filmmaker who has lived in the city for eight years, told CBS News the cost of such a private water supply "would mean about 50% of the monthly income of a significant part of the population."

Ram sent his parents, with whom he had lived in the city, back to their hometown until the water crisis is resolved. That's not expected to happen until October or November, when the rains should begin again.

All four of the primary reservoirs that supply water to the city have dried up, either partly or completely.

On Tuesday, K. Palaniswami, chief minister of Tamil Nadu state where Chennai is located, acknowledged the crisis would continue for about five more months. "Until then we have to meet the requirements only from groundwater sources," he said.

Environmental concerns

"The water table in Chennai is seriously compromised," ecologist and biodiversity expert Dr. Jayashree Vencatesan told CBS News. "There is rampant extraction through bore wells in south Chennai. There are no guidelines; things are in a mess."

Vencatesan has studied 200 years worth of data on Chennai's monsoon seasons. She told CBS News the data analysis by herself and other researchers at the Care Earth Trust show a marked change around nine years ago; while the overall amount of rain has remained roughly the same, the number of days with rainfall have reduced drastically. In other words, more days with severe downpours and less steady, sustained rainfall. That leads to more quick runoff and less flowing in a controlled way into reservoirs.

"This may be a case of climate change," she said.

Climate scientists have warned that the increase in average global temperatures appears to be causing earlier melting of Arctic ice, which can have a broad impact on the Earth's climate over the course of a year -- bringing exactly the kind of dramatic changes in weather patterns that the data from India reflect.

While this year's monsoon will likely bring relief in the autumn, environmentalists believe there needs to be a long-term water conservation plan to avoid such crises in the future -- not just in Chennai but across India.

"Water needs to be treated as a highly limited resource," Vencatesan said. "There is a gap between government policy and the implementation."

An alarming report last year by the Indian government's own research institute, NITI Aayog, warned that 21 Indian cities, including New Delhi, Chennai, Bengaluru, and Hyderabad, would run out of groundwater by 2020.

The report also said 40% of India's 1.34 billion people would have no access to drinking water by 2030. More than 600 million Indians are facing "acute water shortage" already, according to the report.