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Let's look for some fluid solutions
Mumbai has both a flooding problem during the monsoons and periodic water cuts. The solution should be obvious: water harvesting, as Chennai is doing with great results The key benefit for Mumbaikars from rainwater harvesting will be in reducing their dependence on the ubiquitous water tanker
VIJAY KRISHNA



R AINWATER HARVESTING is one of the keys to making Mumbai a more livable city.
As Mumbai continues to grow, bringing water to the city from outside becomes increasingly difficult. We are running out of sources to tap into. As competition for this limited resource intensifies, people outside Mumbai are not going to willingly give up their water for us. Rainwater harvesting is a solution that is literally in our backyard.

How much water can Mumbai harvest? On long-term average, Mumbai gets about 2400 mm of rainfall a year. Taking an area of 437 sq km gives us about 2800 MLD (Million Litres per Day) over the course of a year. So depending on how serious we are about it, we can get anywhere from zero to 2800 MLD of our water requirements from rainwater harvesting. Compare this with Mumbai's current water supply through BMC of about 3500 MLD, of which a fifth or more is lost in leakages, and another 1000 MLD shortfall, which is met from other sources. This should show us that rainwater harvesting has serious potential.

The key benefit for Mumbaikars from rainwater harvesting will be in reducing their dependence on the ubiquitous water tanker. With rainwater harvesting in the rainy season, people should be able to meet their requirements along with the BMC supply In fact several ‘ear . ly adopters' of rainwater harvesting report that the recharging is continuing to give them water even in summer months. From the macro-view, more water from rainwater harvesting means less water needs to come into the city from outside, reduc ing costs, energy consumption, and increasing sustainability and dependability. As more and more people harvest rain, there is going to be a perceptibly positive effect on flooding - something surely no one will complain about.

We must recognise the limitations of the city administration in water supply Despite the talk . of a world-class city and provid ing 24-by-7 water, BMC cannot conjure water out of nowhere. As the city's needs grow, it becomes ever harder to find new water sources and transport the water to the city As a part of the . solution, BMC should aggressively promote rainwater harvesting and legislate it after appropriate preparation. Businesses must recognise that rainwater harvesting is a sound investment for ensuring Mumbai's future. It must be implemented in offices as a matter of course. Housing societies must be helped in implementing it. Asian Paints has set a great example of rainwater harvesting and sound water management - and it has added to its bottomline.

How are other cities faring? In October 2002, the government of Tamil Nadu passed an ordinance making rainwater harvesting compulsory for all residences and giving people a year to construct the facilities. This was after the situation got extremely bad - in 2002, Chennai was getting a jaw-dropping low supply of 194 MLD from the municipal corporation compared to the requirement of 790 MLD. 2004 was a bad monsoon year and 2005 and 2006 were good years. Nowadays, Chennai is seeing rising groundwater levels. For example, a study by Chennai Metrowater showed that between June 2005 and 2006, the average groundwater level in the city was up by 2.5 meters, thanks to water harvesting. The trend of falling groundwater levels has been reversed. Chennai now is better prepared to face a drought year. According to Sekhar Raghavan of the Chennai Rain Center, saline water intrusion, a big problem in coastal areas of the city has come down dramatically, with the level of dissolved salts falling by as much as 80 per cent in some areas- one of the big success stories of compulsory rainwater harvesting. This is something Mumbai also stands to gain from harvesting rainwater. Chennai is also experimenting with largescale desalination, but the cost of water produced by that technology is very high.

Bangalore continues to grow rapidly but it has few water supply choices left. There is only so much water it can extract from the Cauvery and the interstate fight with Tamil Nadu over those waters make that hardly a reliable source. Thus Bangalore too needs to adopt rainwater harvesting and water recycling in a big way or suffer Chennai's painful experience.

There is every reason to make rainwater harvesting compulsory in most cities, including Mumbai. The water crisis is real, and rainwater harvesting is an essential component of the solution. So many housing societies and companies have already implemented rainwater harvesting successfully There is . no dearth of organisations in Mumbai that will offer support in implementing it. Asian Paints runs a Total Water Management Center at its Bhandup office that is free and open to everyone. The company says it has helped people harvest 100 million litres of rainwater to date. Eureka Forbes also offers free rainwater consultancy and has helped many housing societies in setting up their rainwater harvesting systems. L&T Powai, Tata Institute of Social Sciences, St.Catherine's Home, Andheri to name a few are successfully using harvested rainwater. A listing of groups that offer consultancy and design can be found at http://tinyurl.com/2lca98, along with examples of successful rainwater harvesting. With the kind of rainfall Mumbai gets, it is only commonsense that we use the water judiciously and don't seesaw between floods and shortages.

There are some other aspects of the water problem that need to be looked into. One is wastewater recycling, which has enormous potential. There are already working examples that show its viability The other is water con . servation - the best way to implement that is through pricing water at a level that encourages people to conserve. But the pricing should be by slabs, ensuring supply to everyone irrespective of their ability to pay .

Vijay Krishna works for Arghyam, a trust dedicated to water issues


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