Conservation of rainwater

Khalilur Rahman | Published: June 15, 2014 00:00:00 | Updated: November 30, 2024 06:01:00

Experts at a meeting held in the city last week stressed the need for conservation and use of rainwater in major cities. They expressed apprehension that indiscriminate extraction of groundwater will cause land subsidence and increased salinity. WaterAid and Bangla daily ProthomAlo, organised the meeting on the conservation and use of rainwater in cities. Speaking at the meeting, Dr. Ishrat Islam, professor of urban planning, Bangladesh University of Engineering and Technology (BUIT), said wetlands which store rainwater are being filled up inviolation of Dhaka city's master plan.
Ponds, canals and other water bodies in and around Dhaka city which serve the purpose of storing rainwater and help recharge aquifers are disappearing in the fast tempo of urbanisation. According to an official estimate, underground water table in Dhaka city is depleting by three metres annually. This is really an alarming situation.
The managing director of Dhaka Water Supply and Sewerage Authority (WASA) disclosed at the meeting that at present WASA can meet only 22% of the total need of water of the city dwellers per day from surface water source and the rest is extracted through deep tubewells. He, however, assured all concerned that the Dhaka WASA plans to reduce dependence on groundwater substantially by tapping surface water sources.
The water supply system in the city mostly depends on deep tubewell network. The rivers around Dhaka city which could provide surface water to the city dwellers are now heavily polluted and, therefore, remain beyond treatment. The river Buriganga, Turag, Balu and Shitalakhya are in the grip of land grabbers who find it convenient to develop housing schemes by filling those.
Joint secretary of Bangladesh Poribesh Andolon architect Iqbal Habib informed the meeting that the government has allowed a large housing project on flood flow zone in Rupganj of Narayanganj district. The river Balu and Shitalakhya flowing there could be used as sources of surface water.
The experts at the meeting were of the opinion that harvesting of rainwater can reduce pressure on groundwater substantially. Therefore, devices for conserving rainwater can be installed at big public buildings, stadiums, railway stations and airports.Â Sheikh Abdul Mannan, director of Rajdhani Unnayan Kartripakkha (RAJUK), the lone city development authority, told the meeting that the RAJUK was set to make provisions for harvesting rain water in its building code.
We know that harvesting of rainwater has been proved effective in various countries of the world. During monsoon the Dhaka city experiences rainfall of about 2000 mm. The rainwater may be stored on rooftops during this period. About 65% of the city area is paved and the wetlands around the metropolis have also been filled up by the developers for housing projects. If half of the rooftops in Dhaka city can be utilised for storing water during monsoon, the demand of citizens for water supply will be met to a great extent.
The government may launch mass awareness campaign to encourage people owning existing buildings to make provision for conserving rainwater. The rain water, thus collected in the rooftops, may be supplied to underground tanks through pipes. The owners of old buildings may be provided with loans on easy terms for making provisions to retain rainwater on their rooftops.
Measures so far taken by the government to make rivers around the capital -- the Buriganga, Shitalakhya, Turag and Balu -- free from pollution have yielded no result. The water, drawn from the river Buriganga and treated at Dhaka Water Works in Chandni Ghat, is unfit for human consumption. But a large section of population in old parts of Dhaka city still depends on supply from Dhaka Water Works.
Drastic fall in underground water table is not confined to cities and towns alone but it also prevails across the vast rural areas of the country. The parliamentary standing committee on ministry of agriculture had earlier recommended that the government should take emergency measures to reduce dependency on groundwater for irrigation as the underground reserve has fallen drastically during the last several years.
The parliamentary panel also asked the ministry of agriculture to encourage people to use surface water and called upon the government to undertake region based-development plan with emphasis on environmental factors.
(Email: khalilbdh@gmail.com)