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Metrowater plans rainwater harvesting audit

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The Hindu         04.08.2017 

Metrowater plans rainwater harvesting audit

Earlier sample study found poor maintenance in 30% of structures; Existing mechanisms have potential to add 2.7 tmcft to groundwater every year

In an effort to assess the impact of rainwater harvesting (RWH) measures and ensure water security in Chennai, Chennai Metrowater is planning to conduct an audit of RWH structures across the city. The exercise is expected to begin in a couple of weeks.

The water agency plans to have the audit with community participation and support from voluntary organisations as it does not have sufficient manpower on its own.

According to Metrowater’s data, there are nearly 8.62 lakh RWH structures installed in the buildings across the city. During the last fiscal, 15,200 structures were constructed as it was mandatory for obtaining new or renewal of water and sewer connections.

Metrowater officials said if the RWH structures were found to be poorly maintained, residents would be sensitised about the need for maintenance. Bulk consumers like hospital and educational institutions would be asked individually to maintain such structures. “We have to decide on the methodology to be adopted for the audit. The options of using digital technology are also being considered,” said an official. Residents could also attend awareness meetings planned by the Metrowater in various areas.

Metrowater is also planning to strengthen its hydro-geology wing by recruiting or outsourcing services of graduates from Anna University. The team would be used to map the city’s aquifers, identify new water sources and also encourage implementation of greywater recycling in Chennai’s buildings.

Design change

An audit of RWH structures taken up by Rain Centre, a city-based voluntary organisation two years ago, is perhaps the only comprehensive audit available so far. The organisation was assigned the project by the Chennai Metropolitan Development Authority (CMDA).

The audit covered 1,200 households spread over the city with sandy, clayey and rocky soil. Kottivakkam, Anna Nagar, Thiruvanmiyur, Velachery and Tambaram were some of the areas covered. Sekhar Raghavan, the Centre’s director, said: “We were asked to conduct the audit in fast-developing added areas. We found that 90% of the households had RWH structures. But, 30 % of them were poorly maintained. Many multi-storeyed buildings did not have RWH structures.”

Some of the recommendations included change in RWH structure design and implementation of water metering system. The recommendations are waiting to be incorporated in the Development Control Regulations of CMDA.

Installing rainwater harvesting structures has also gained momentum in town panchayats.

According to sources, nearly 24.31 lakh buildings in town panchayats across the State have constructed such structures.

Across the State

Though it was estimated that recharge potential would be increased to 4,800 million cubic feet as most buildings in the State claimed to have RWH systems, the water table dipped up to 16.5 feet this year in some parts of the State.On the impact of RWH, Mr. Sekhar Raghavan said percolation pits that are suggested by the government agencies would need to be replaced with recharge wells as pits get silted up and cannot be reused.

Environmental activists also noted that the misuse of water bodies has led to the depletion of groundwater resources. Kanchi Amudhan, convenor of Palar River Protection Movement, said that deliberate breaching of bunds of smaller water bodies has compounded the problem further.

( With additional reporting by V. Venkatasubramanian )