Rainwater goes down drain

Rainwater goes down drain

Harvesting Could Have Prevented Waterlogging: Experts

Neha Lalchandani | TNN

New Delhi: Looking at those photographs of the flooded Dwarka underpass, if you were marvelling at the amount of water that had turned it into a swimming pool, heres some food for thought. According to the Forum for Organised Resource Conservation and Enhancement (FORCE), a Delhi-based NGO, the quantity was 10-12 .5 crore litres. Going by the international norm of 135lt/capita/day as the average requirement of water for each person, this quantity would have been enough for 7.5 lakh people for a day!
Experts argue that had the government got its rainwater harvesting mechanism in place, the city would not have been waterlogged after receiving 126 mm rain that it did on Monday. It was also the perfect opportunity to replenish a part of Delhis fast-depleting water table. On Monday, there was massive water accumulation not just in Dwarka but also at the Moolchand underpass, on many roads and at the foot of several flyovers, leading to huge traffic snarls.
Despite court diktats ordering rainwater harvesting on flyovers and roads, the government has done precious little. According to Central Ground Water Board figures, Delhi receives an average of 611.5mm rain over 27 days in a year. This translates to roughly 19,277 crore litres.
If the Dwarka underpass had a good rainwater harvesting system, a lot of the water that went waste could have actually been put to good use. An underpass is an artificial depression dug out from the ground. Drainage in an underpass is always a problem because its almost always impossible to align the slope of the underpass drainage with that of the main drain outside the underpass. It is important to ensure that the drainage for surrounding catchments is planned in such a way that all water gets diverted away from the underpass before it enters the depressed zone. The other option is rainwater harvesting , said Jyoti Sharma, president , FORCE.
According to Vinod Jain, director, NGO Tapas, while efforts are on to install rainwater harvesting units in buildings , very little has been done on roads. According to an affidavit filed by various agencies , only a couple of roads and very few flyovers, including the Safdarjung and Dhaula Kuan flyovers, have rainwater harvesting facilities in place. At most flyovers, claimed Jain, the designing was poor and not at all effective.
Sharma, who has been involved with several rainwater harvesting projects in the city, claimed that unless the systems are maintained well, just constructing them would serve no purpose. Many structures in the city are either poorly planned or not maintained at all, making them highly ineffective. If regular cleaning is not done, the system gets choked and becomes defunct. The cleaning is especially necessary where the rainwater harvesting system takes water from roads or open surfaces where the silt load is high, said Sharma.
According to a Delhi Jal Board official, rainwater harvesting is still very unplanned. While several buildings, both private and government, have started water harvesting, unless the entire city takes to it in a systematic manner, there will be little benefits to reap from it, he said. Sharma suggested that rainwater harvesting systems should be integrated with the stormwater drainage systems so that regular maintenance of both can be carried out.
Experts also believe that in providing structures on roads and flyovers, drainage and water harvesting need to be coordinated . The civic agency constructing the underpass would have had jurisdiction only over that stretch of road and their designing and implementation would have been without coordination with other agencies incharge of nearby roads. Since water harvesting is seen in isolation and is done in a totally piecemeal manner, it is not surprising that plans very often do not work, said Sharma.

WHAT A WASTE



On July 27, the city received a total of 126 mm rainfall



The Dwarka underpass, on a 1.5-km stretch, remained under water for 4 days Height of water column at deepest point was 20 feet



Around 10-12 .5 crore litres of water accumulated at the spot



Going by annual rainfall figures, this area could hold about 40-50 crore litres of water annually



10 crore litres is daily requirement of 7.5 lakh people or annual requirement of 2,000 people