Rainwater harvesting is the key to conserving water and staving off drought. Dhanishta Shah speaks to geologist Dr Amar Joshi to understand the process and misconceptions around it
With more than 25 per cent of India's population estimated to be tackling a crippling drought and an above normal monsoon expected this year, harvesting rainwater not just to store it for future use but also to recharge underground aquifers is critical.
Revising its monsoon prediction, private weather forecaster Skymet has said rainfall this year will be 109 per cent of the long period average (LPA), up from the estimated 105 per cent last month. El Nino, the weather condition in the Pacific that impacts the South Asian monsoon, has ended, signalling hope for millions of people in India's 11 drought-hit states. But this will mean only momentary relief if the water is not conserved the proper way, say experts.
In this scenario, rainwater harvesting, the age-old system of collection of rainwater for future use, has generated a lot of interest. But there are several misconceptions. It is not as simple as installing a tank on the ground level and storing water in it! A good rainwater harvesting system has to be one that provides a permanent solution. It not only stores rainwater, but uses it to recharge the aquifer (rock formations that carries and transmits water) lying under ground.
Detailing the whole process, renowned geologist Dr Amar Joshi says there are, to put it simply, three steps – inspection, installation and maintenance:
1 There needs to be an inspection of the area in order to understand the what kind of system would work best. An expert can calculate the potential amount of collectible water in any area by using a formula. When a place gets seasonal rain, it makes sense to use rainwater to recharge groundwater aquifers, from where one can draw water throughout the year.
2 The system will be designed based on the unique requirements of the site. The focus is on collection, filtering and storage of the rainwater. The water passes through a simple filter system. It then reaches inside the ground, from where it can be taken up through a bore well or open well.
3 Rainwater harvesting methods are site specific and hence it is difficult to give a generalised cost. It varies widely depending on the availability of existing structures like wells and tanks, which can be modified and used for water harvesting.
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