The reality of Chennai's dependence on rain is not fully appreciated. If it were, then rainwater harvesting (rwh) would have been looked upon as a social obligation. Considering the annual average rainfall of 1,280 millimetre in the city area of 174 sq km, the annual rainwater harvesting potential is about 222 billion litres, which means 608 mld. The city's water demand is 880 MLD. There are two aspects of RWH: lakes in the open areas and rooftops in built up areas.
After the severe drought of 1992 and 1993, Metro Water began a actively promote RWH. It worked out a 'statutory understanding' with the Madras Metropolitan Development Authority and the Chennai Municipal Corporation: they would accept building applications only if they included a proposal of RWH. But this was totally ineffective. Several approved buildings either lacked RWH systems or the structures were inadequate. A sample survey, conducted by the Madras Institute of Development Studies in 2002 at the behest of the Centre for Science and Environment (CSE), shows that of the 75 buildings approved for construction in 1997 and 1998, two-thirds had not installed any RWH system despite showing it in the map. In 1994, the state government made RWH compulsory for multi-storey buildings. In 2001, it became mandatory for all buildings. But people made RWH structures more to meet the building criteria than to solve their water crisis.
The state government then issued an ordinance in 2002, imposing a strict deadline for implementing RWH in all buildings. With chief minister Jayalalithaa embracing RWH with zeal, it has become a buzzword in Chennai, showing other cities the benefits of this time-tested system. This ordinance, claims Metro Water, has had such an impact that all the houses in Chennai have RWH.
A CSE survey in January 2004 found 86 per cent of the households had implemented RWH. (The survey also found that Chennai residents opted for a small percolation pit with a shallow borewell merely to meet the legal requirements.)
Shekhar Raghavan of Akashganga Trust, an NGO in Chennai, conducted a household survey on the effectiveness of RWH in Gandhinagar area from June to October 2003. It covered 309 independent houses and found that only 50 per cent had implemented RWH properly. The parameters he looked at included system implementation, apportioning of water, design and maintenance of water to ensure silt removal.
"In many homes, RWH is not done scientifically, the surface runoff is not harvested," he points out. The CSE survey had also found that 65-70 per cent of the households implemented RWH with designs obtained from either a plumber or developed on their own, indicating lack of technical guidance.
While the government effort to promote RWH is commendable, it is clear that legislation by itself will not make any difference. It needs stricter enforcement. Civic/community groups have to take up its monitoring and implementation. The RWH imperative has not got woven into the social fabric. But not all people have to be goaded into RWG.
K Venkatraman retired from the army and came back to his house in Padmanabhanagar in Adayar. His found the public supply inadequate, the groundwater brackish. As president of the residents' welfare association, Venkatraman initiated rwh in 1999, much before Jayalalithaa made it mandatory across the state in 2003. He began by installing a simple PVC pipe to divert rainwater. Several others in the 110-house colony followed his example. "Even during the worst crisis, water was available in borewells in our houses at 10 metres," he beams. The groundwater level in the neighbourhood has increased to a comfortable level and only a few households had to purchase water during the drought this year, while adjacent areas depended heavily on private tankers during the summer. "The annual potential of harvesting water in these 110 homes is to the tune of 14 million litres," says Venkatraman.
But the fuss over rooftops has taken attention away from the traditional way of recharging aquifers: maintaining lakes and tanks. Chennai has about 200 lakes, including about 35 temple tanks. Constant depletion of groundwater, encroachment of the lakes' catchment, and diversion of inlets has rendered most of these waterbodies dry. Tanks like Pallikaranai and Ambattur are endangered. The main threats: the housing board and the municipality.
In the city's rush to grab water from waterbodies far and away -- the Veeranam lake, Krishna river -- Chennai's waterbodies have been forgotten. The Citizen Consumer and Civic Action Group (CAG),an NGO, holds the Tamil Nadu Housing Board responsible for destroying several lakes. CAG filed a public interest petition against the board, but by the time the case was heard, the lakes had been filled up. About 58 hectares (ha) of a lake in Ambattur were taken over by the board for a housing project. Three-fourths of the Chittilipakam lake has been taken over. Around 18 ha at Kakallur lake have also been eaten up, says Bharath Jairaj of CAG. At Velachery, eight ha of Lakeland have been filled up by the slum clearance board and the housing board, he adds. The Pallikarani marsh, once a large nesting ground for birds, is now a 120-ha dump yard. The government might be keen on rainwater harvesting, but it has destroyed Chennai's waterbodies.
The A M Murugappa Chettiar Research Centre, an NGO, surveyed 36 temple tanks in Chennai. Their aggregate storage capacity of 0.5 million cubic metres is sizeable, and can make a significant difference to groundwater recharge in the city. But most are dry or get only limited inflows; several are in a state of disrepair -- broken sidewalls, water hyacinth infestation, silted tank beds. Most tanks are used as public conveniences for garbage disposal. The ngo suggests the following:
reconstruction of the boundary wells and, where possible, increasing their height
identification and removal of impediments to inflow of runoff; and
measures to increase the rate of percolation into the ground.
But it is an uphill task to ensure that even as storm water drains are desilted and kept clear, sewage does not contaminate the water inflow. Along with these measures, local communities need to be mobilised. There are some good examples.
After successfully implementing RWH in their houses, about 1,000 residents of the Pammal locality have now moved on to restore their temple tank. "Once we began the desilting and cleaning operations, lots of people came forward to help in different ways like technical advice, monetary help or voluntary labour," says Indra Kumar, a Pammal resident.
The first to draw attention to the pathetic state of the lakes was Mangalam Balasubramanian, head of the Pammal Ladies Club. This led to the club holding a fund-raising campaign. Its members went from door to door. About Rs 13 lakh were raised. More than half of the fund went to strengthen the banks of the tank by constructing a wall around it. Residents are happy with the results. "In May 2004, we had 3.5 metres of water as compared to 1.2 metres in 2003," says Indra Kumar. Both the quality and quantity of water in the region has improved after the tank's restoration.
There are several tanks that can be transformed in a similar manner. "Desilt the 600 lakes in Chennai, Chengalpattu and Thiruvallur districts or construct check-dams along the Adyar and Cooum rivers to solve the water crisis," reckons V Subramanian, president of Water Bodies Protection, an NGO.