gopi: the group at the back, please come closer.all started in 2017 when coimbatore was facing a severe drought. manikandan was determined to revive one of the city's driest water bodies. manikandan: it was the perur tank. it hadn't received water for many years. we decided to clean the tank by removing plastics and invasive weeds in them. we began cleaning activities on the 12th of february 2017. in the first week, 50 showed up. but in the weeks after, 400 ople showed up. in just a month, we finished cleaning the tank. we don't have a financial or political background, but we had volunteers who were ready to work for this. so, we decided to clean-up various water bodies every sunday. so far, we have been working for 249 consecutive sundays. reporter: the organization has resred four large lakes, nine small ponds, and more. but if you ask manikandan which project was hardest, he'll insist on taking you there, before he tells you the story behind it. manikdan: this is vellalore. reporter: spread across 90 acres, the vellalore tank is