A recent study shows that the groundwater level in Dhaka city is falling at a rate of 9.21 feet per year. During the last seven years, the groundwater level has registered a fall of 65.61 feet. Indiscriminate use of groundwater is responsible for this alarming situation. UnnayanOnneshan, a private think tank, in its study reveals that the water table in the city will fall by more than 393 feet within 2050 if the underground water continues to maintain the present rate of depletion. The Bangladesh Agriculture Development Corporation (BADC), a state-run organisation, conducted a research two years ago on groundwater level. The BADC findings say the water level in 416 observation wells fell at a depth below the mean sea level during the period between 2004 and 2010.
In Dhaka city, alarming fall in groundwater level has prompted the Water Supply and Sewerage Authority (WASA) to embark upon a plan to recharge aquifers with rain water. This is for the first time that Dhaka WASA has taken steps to overcome the crisis arising out of depleting groundwater table because of widespread use of deep tubewells to meet the growing need of water for an ever-increasing number of townspeople.
The WASA authorities, according to press reports, have taken a plan for massive recharging of underground aquifers at a minimum cost. It also plans to reduce the dependency on groundwater by 50% during the next one decade by installing water treatment plants in different city areas. The plants will treat river water. At present nearly 88% of the total water production of Dhaka WASA comes from more than 600 deep tubewells and the rest from the existing water treatment plants.
In view of so much dependence on groundwater, the Dhaka WASA undertook a scheme more than three years ago to harvest rain water in the city but the project remained stalled due to bureaucratic bottleneck. In 2012, the project started on a trial basis.
As we reported earlier in this column the government has now decided to amend the Building Construction Rules 2008 with a provision to make harvesting of rain water mandatory for all new houses in Dhaka city. Under the proposed rule, the new buildings will have to retain rain water. The Rajdhani Unnayan Kartripakkha (RAJUK), the lone city development authority, says that the amendment to the existing construction rules will facilitate harvesting of rain water as well as groundwater recharge.
We know that harvesting of rain water has been proved effective in various countries of the world. During monsoon the Dhaka city experiences rainfall of about 2000 mm. The rain water may be stored on rooftops during this period. About 65% of the city area is paved. The wetlands around Dhaka have also been filled up by the developers for housing projects. If half of the rooftops in Dhaka city can be utilized for storing water during monsoon the demand of citizens for water supply will be met substantially. The government may launch mass awareness campaign to encourage people owning existing buildings to make provision for conserving rain water. 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 rain water on their rooftops.
In rural areas of the country where the growers now depend heavily on groundwater for irrigation because of silted rivers and canals find it difficult to operate deep tubewells for the fall in aquifer level. In many places deep tubewells, set up for irrigation, have turned totally inoperative. The farmers are, therefore, facing great difficulties in maintaining irrigation for growing crops. The permanent solution, however, lies with making surface water available for cultivation round the year.
In order to achieve this objective excavation of canals, rivers and other water bodies is urgently needed. This is a gigantic task involving huge expenditures. Therefore mass awareness campaign should be launched to encourage people to come forward and participate voluntarily in canal and river digging programmes. As mechanical dredging of rivers is too expensive, the able-bodied rural people can be engaged in excavation projects under food for work programme (FWP).
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