t is no longer about rainwater harvesting. It is about applying the right harvesting technique in a given situation. According to a study conducted by Rain Centre, a city-based voluntary organisation, rainwater harvesting techniques have to vary from location to location.
The study has divided the city into four recharge zones, based on soil formation and recharge potential.
According to the study, areas along the coast and river banks such as Besant Nagar, Triplicane, MRC Nagar, Royapuram, Spurtank Road and Gandhi Nagar have the potential to recharge every drop of rainwater that falls on their soil. Besides sandy soil, these areas also have a low water table before the onset of the monsoon, which favours faster percolation.
The study has urged residents to ensure utmost harnessing of rainwater at their houses, including driveway runoffs. It has asked the government to dig recharge wells along road margins to replenish groundwater. Recharge wells dug on the roadside at Kalakshetra Colony, Besant Nagar, have helped these areas escape flooding. Areas such as T. Nagar, parts of West Mambalam, Kilpauk and Ayanavaram fall under recharge zone II, which is characterised by sandy soil, but has a high water table.
However, areas that have clayey soil and rocky terrain need a different rainwater harnessing technique to sustain groundwater source.
Mr. Raghavan said these areas, with their clayey soil are categorised as recharge zone III, despite a low water table. “Having an open space need not necessarily mean good rainwater recharge. In such locations, recharge wells are necessary to improve the groundwater table,” he said.
There are certain other areas in the city where harnessing rainwater may prove difficult owing to rocky terrain, says the study. In areas such as Little Mount, Pallavaram, Saidapet, Alandur and St. Thomas Mount, residents may have to put up a combination of a recharge well and a borewell pit.
The Rain Centre also plans to survey rainwater harvesting structures and provide suggestions to residents. People may either contact the Centre on ph: 24918415 or 9677043869, or the Chennai Metrowater at ph: 28454080 and 45674567 to clarify doubts on the maintenance of such structures.