With water supplies shrinking to crisis levels in the Indian metropolis of Chennai, one key solution has been overlooked - persuading residents to use less water, said the man in charge of reducing city risks.
Krishna Mohan Ramachandran, Chennai's chief resilience officer, said water was flowing in the taps only once every three days in the manufacturing hub, where the government provides a little over half of the water supply with the rest coming from private vendors.
In recent weeks, people living on the outskirts have tried to stop water tankers filling up at local wells, fearing their supply was being taken for the city's wealthier residents, as well as hotels and businesses.
Encouraging everyone to use less water would be the surest way of easing shortages and social tensions, Mohan said.
"The one short-term measure that can work for Chennai is to really control the demand for water through better awareness and action from our citizens," said the former advertising executive.
But few ordinary residents know how much of a difference cutting back could make, said Mohan, adding people have continued to water their gardens, wash cars and leave taps running in sinks despite the city's water crisis.
"The citizens are quick to point fingers at the government, but they are not lifting a finger to actually conserve water at home," he told the Thomson Reuters Foundation on the sidelines of a conference on resilient cities in Rotterdam this week.
Groundwater levels and reservoirs have been dropping fast in the area around Chennai, in India's southeast, mainly due to bad water management and weak rainfall during last year's monsoon.
Longer term, the city must expand its ability to capture and store rainfall so it can be reused, as well as recycling waste water, Mohan said.
A new resilience strategy to help the city cope with a range of shocks and stresses - including climate change and urban expansion - includes projects to help Chennai protect and rehabilitate its 3,600 lakes, ponds and canals.
But to deal more quickly with water shortages, Mohan's team, based at the Greater Chennai Corporation - the civic body that governs the city - has planned a campaign to educate the public on the need to save water and to show some simple ways to do it.
Once funding is secured, mainly from the 2% of budgets local companies must allocate to social responsibility measures, the campaign - devised with advertising agencies - should launch in early October, he said.
Monsoon rains usually start soon after that in Chennai, but Mohan believes the campaign can still be effective - though he admits it ideally would have run earlier.
The campaign, using short videos and other social media content as well as outdoor posters in English and Tamil, will warn people that water could eventually cost more than fuel if shortages persist.
Households now pay just $1 a month for an unlimited amount of water through the taps, Mohan noted.
Less than 10% of water is metered and previous government attempts to expand metering have failed, according to the city's resilience strategy.
Mohan said it was possible to buy a tap-fitted device for less than $1 that cuts water flow by 50% but boosts pressure - yet less than a half percent of homes use one.
"If we can do that on a larger scale, it can definitely make a difference," he said.
Simple, free measures the campaign wants to promote include putting a plastic bottle filled with water in the toilet cistern so less is used with each flush, and capturing water expelled by air conditioning units in a bucket to wash cars.
Cape Town success
The idea for the awareness campaign evolved from a two-year effort to craft a city resilience strategy. That plan was released in late June and backed by the 100 Resilient Cities network, of which Chennai is a member.
The water saving campaign was also inspired by the South African city of Cape Town, which faced severe drought in 2017-2018.
It successfully used social media and other communication channels to persuade residents to cut their water use to just 50 litres each per day, averting a feared "Day Zero" when taps would be turned off.
India's government estimates daily water needs in communities with flushing toilets at a minimum of 100 litres per person.
Cape Town started talking about "Day Zero" when its reservoir levels dropped to 15%, Mohan said, whereas those in Chennai were now as low as 6%.
To maintain water reserves and reduce flood risks, the resilience plan includes measures such as protecting marshlands from construction and keeping canals and water bodies free of garbage so they can store more water.
In a foreword to the strategy, Greater Chennai Corporation Commissioner G. Prakash noted that, after major floods in 2015, the city had started harvesting rainwater at offices and campuses, as well as restoring traditional temple tanks, ponds and lakes.
Mohan said the city's previous focus had been on installing stormwater drains to channel heavy rainfall to the sea as fast as possible to avert flooding.
"That's ridiculous because we should be conserving that water," he said. "The government's thinking is changing."