A conservationist makes rainwater harvesting his mission in Guwahati

He strongly believes in practicing before preaching. Dr. Dipul Choudhury, an eye specialist based in Guwahati, seizes every single opportunity to talk more about the benefits of rainwater harvesting than his own medical profession.

“Rain water harvesting has multiple benefits. If every household in Guwahati harvests rainwater then it will reduce the amount of rainwater discharge from city households to the roads and drainage system and will reduce the intensity of water-logging in city localities. It helps recharging of ground water sources. By using stored and treated rain water we can minimise the use of underground water. It also helps in saving energy and keeping the energy bill at the minimum. Besides, it also lengthens the mechanical life of a water pump,” he says. Dr Choudhury says all this with much confidence because of his practical experience of rainwater harvesting and deriving these benefits for the past 22 years.

The past experience of rainwater harvesting inspired Dr. Choudhury to go for a rooftop rainwater harvesting system with a capacity of 1.60 lakh liters in a five-storied building in Guwahati. All the rainwater that falls on the rooftop is drained through a pipe system and is allowed to flow through a sand filter after baffled sedimentation before storing it in two partly underground storage tanks of six feet depth. In 1991, Dr Choudhury set up his first rainwater system with 9000 liter capacity designed by himself.

Public Health Engineer Nripendra Kumar Sarma, who designed the rainwater harvesting system built in the five-storied building of Dr Choudhury and his family, feels that the Guwahati Municipal Corporation (GMC) and the Guwahati Metropolitan Development Authority should not allow construction of any new building that does not have a proper rainwater harvesting mechanism as part of the building design. Mr Sarma also helped Dr Choudhury put up a waste-water management system to ensure that there is no discharge of wastewater from the building to the storm-water drain outside the campus. The waste water is treated by passing it through an anaerobic baffle reactor followed by an up flow through an anaerobic filter. The treated waste water is then allowed to flow to a 10-feet deep well dug in the compound.

To supplement these green efforts, Dr Choudhury has used specially designed hollow bricks for construction of the outer walls of the building. Mr Sarma says that because of the hollow bricks, the room temperature will be four to five degrees less as compared to buildings constructed using solid bricks. Thus use of hollow bricks can make air-conditioners redundant in Guwahati which in turn will go a long way in reducing carbon footprint of the city.

While few enthusiasts like the doctor have been making individual efforts to make the city greener, efforts such as waste water management, using hollow bricks in building construction, solar water heater, more particularly rain water harvesting, is yet to find acceptance among the residents of Guwahati despite the bitter truth that piped water supply covers only 30 per cent of the city’s 963,429 population (2011 Census) when the gap between water demand and supply is widening with rapid horizontal and vertical expansion of the city.

Being the gateway of northeast India, Guwahati city also has to cater to a huge floating population. However, in most areas covered by piped water, supply gets contaminated water as the pipe network servicing the existing water works facilities has outlived its life and has leakages all over. Three water supply projects undertaken by Guwahati Metropolitan Development Authority (GMDA) with the objective of providing metered round-the-clock safe drinking water are now in various stages of implementation with funds from Japanese International Cooperation Agency (JICA), the Asian Development Bank (ADB) and the JNNURM.

Ground water, extracted by those who do not have access to treated piped water, has high iron content in most areas and fluoride content in some pockets. It is not fit for drinking without proper treatment. The water table of the city, on the other hand, is going down alarmingly due to over dependence on it by city residents and also because of decline in recharging of underground aquifers as more and more open areas are getting covered with concrete construction due to rapid expansion of the city. As a result, the extraction of ground water has also become very costly as one has to bore to the deeper level to pump up water from underground sources. Increasing number of water pumps has also pushed up the energy consumption in the city. Yet, for the city residents rainwater harvesting has remained a mere catch line for workshops and seminars.