Rainwater, believed to be the safest source of drinking water, may not be safe to drink if rainwater harvesting system (RWHS) is not managed properly, experts said that at a session titled ‘Promotion of urban rainwater harvesting and Recharge” hosted by WaterAid on the second day of “Annual National Conference on Urban Resilience to Climate Change 2019,” at the Institute of Architects Bangladesh (IAB) on Wednesday.
Asian Cities Climate Change Resilience Network (ACCCRN), and International Centre for Climate Change and Development (ICCCAD) jointly organized the event.
During the session, experts informed that Rainwater harvesting system (RWHS) comprises components of various stages -transporting rainwater through pipes or drains, filtration, and storage in tanks for reuse.
They also said that rainwater is an important alternative for water challenged areas where water has salinity or arsenic problems, but the success rate of rainwater harvesting system (RWHS) in those areas is still fairly low in the country.
Dr Tanvir Ahmed, professor of the Department of Civil Engineering of Bangladesh University of Engineering and Technology (Buet) said: “Rainwater is safe and pure. But we have to store rainwater for reuse, and the problem starts from there, as rainwater may get contaminated if the reservoir or tank is not cleaned regularly.
Tanvir said: “There are mixed results when RWHS was tried in arsenic prone areas especially in dry seasons as many reservoirs were found empty, and not cleaned properly, which showed that people in those areas are still unaware about RWHS procedure,” he added.
Mohammad Golam Muktadir. Technical advisor of WASH, WaterAid Bangladesh said, “According to the world health organization arsenic-contaminated water directly affects the health of 35 million people in Bangladesh.
“Bangladesh has no water scarcity. But at present, safely managed water coverage is only 55% due to contamination, and pollution. 80 rivers are about to die while 100 have lost their natural characteristics due to withdrawal of water in the upstream. So an alternative source of drinking water such as rainwater is important.” he said.
“WaterAid installed more than 7000 different rainwater harvesting system in Bangladesh. Since 2010, we are providing training of professionals, and stakeholders on the system. Government is now considering RWHS as an alternative water supply option, to be implemented in hilly and coastal areas. Different NGOs, and other organizations are also installing RWHS,” he said.
“Technology improvement is making periodic maintenance easier, he claimed.
In case of urban areas, experts suggested using rainwater for other uses like watering gardens, washing cars, and toilet flush, rather than drinking it. They also said it is not cost-effective for small holdings. But emphasized on making it mandatory for high-rise buildings.
Dr Fahmida Khanom, Director (Natural resources and research) of the Department of Environment said: “It is difficult for a house owner of small holdings to install two water tank parallelly as it is costly. Maintenance is also tough. But in the case of high-rise buildings, industrial units, schools, colleges and hospitals, the Government should impose a mandatory section of RWHS.”
Abdullah Al-Muyeed, head of policy and advocacy at WaterAid Bangladesh said: “A single chapter on RWHS was incorporated in Bangladesh National Building Code but since 2008 BNBC draft has not been finalized.”
Dr Kazi Matin Ahmed, professor of the Department of Geology of the University of Dhaka presided over the session.
Rainfall generates 200-250 billion cubic metres of water per year. The basic requirement of water except in-stream, and environmental needs is 160 billion cubic metres per year. Rainwater alone can meet the basic requirements of water in Bangladesh.
