Bridging the Clouds & the Aquifers
India is blessed with adequate rainfall, yet there are large pockets of dry, drought prone areas and in many other places the quality of groundwater is not good. In such places rainwater harvesting can provide not just sufficient but surplus water for survival. Only a minor percentage of rainwater is harvested. The rain water falling on roads, private/government vacant places and play grounds ,etc straight away reach the nearby drainage and ultimately mixes with sewage water. As a result of this, the entire rain water becomes polluted and eventually it contaminates the ground water. Decentralized water harvesting and ground water recharging is a striking response to the water scarcity and ecological crisis perpetuated by the growing problems of ground water depletion and quality deterioration in any region.
Coimbatore District is situated in the Noyyal River basin and more than 50% of area forms hard rock terrain with local depressions and undulations. Total area of the district is 3670 Sq.km with a total population of 3.75 Million (as per 2011 census). The average annual rainfall of Coimbatore is 700mm. During monsoons and heavy rainfall, the runoff rainwater gets accumulated in the sub-ways and forms pools at low lying culvert crossing areas. The excess runoff water from the elevated parts along the road sides, empty places and over the roof of the building runs off and reaches the low lying depressed part of land very quickly. As very little soil cover exists along the path, it forms a pool of water causing innumerable hardships to the citizens and not to mention the heavy traffic.
Studies show that with 100 mm rainfall on 1 hectare of land, 1 million liters of water can be harvested. This clearly shows the need for rainwater harvesting structures. If the runoff water can be diverted so as to reach the aquifers, the havoc and panic caused by the accumulated and pooled water bodies can be reduced and eventually it will pave way for a a water surplus ecology rather than a scarce environment.
In line with this, Siruthuli conducted a geo-hydrological investigation in 2004 to arrive at a suitable method of artificial recharge to underground aquifers. The study revealed that as Coimbatore is a region with hard rock strata from the top layers itself, recharge structures with deep borewells, that can directly feed the aquifers are the best solution for improving the groundwater table.
In Phase 1, 150 RWHS were constructed in 2004-05 with the financial assistance of Coimbatore Corporation. These structures were rejuvenated in 2009, with the financial assistance from the Rotary Clubs of Coimbatore. Seeing the efficacy of this, the Ministry of Water Resources, New Delhi granted Rs 1 crore of funding for constructing 85 nos of road side Rain Water Harvesting Structures and 130 open space Rain Water Harvesting Structures. This project started in December 2009 and completed in 2012. Thus far we have constructed 365 structures to harvest the Rain Water falling on road and open space of the city.
A recent report published by MoWR, New Delhi regarding a study that was conducted at 1161 locations in TamilNadu for 10 years from 2001 –2011 reveals that the groundwater levels of Coimbatore District have been raised by 13.92 meters, thus ranking Coimbatore as No. 2 in TamilNadu.