Integrated Water Resource Management for Mega City: A Case Study of Dhaka City, Bangladesh - page 2

Fig01
Figure 1: Demand, supply and deficit of water in Dhaka City

 

Figure 1 shows the demand, supply and deficit trend for Dhaka City since 1963. The total water demand for Dhaka City was increased from 150 million liter (ML) in 1963 to 1760 ML in 2003. In 1963 the total deficit for water supply in Dhaka City was 30 ML, which substantially increased to 260 ML in 2003, while Figure 2 shows the present and future water demand scenario in Dhaka City.

Though the city is surrounded by four rivers: the Buriganga, Balu, Turag and Tongi Khal, only about 14.18% of supplied water, as showed in Figure 3, is obtained from these rivers. The water of the surrounding rivers and lakes has already exceeded the standard limits of many water quality parameters because of the discharge of huge amounts of untreated and municipal wastes. Treatment of this water has become so expensive that water supply agencies are almost entirely dependent on the ground water aquifer for their potential alternate source of supply. It is observed that the annual abstraction in the public sector has increased from 177 million cubic meters (MCM) in 1990, to 562 MCM in 2008. The number of private wells has increased from 130 in 1990 to 289 in 1999. This number significantly increased to 1179 in 2008. 

As an outcome, upper parts of the aquifer have become dewatered throughout the area, except for the northeast and southeast corner of the city.

Dhaka has a hot, wet and humid tropical climate. The city is within the monsoon climate zone, with an annual average temperature of 25°C. Nearly 80% of the annual average rainfall of 1,854 mm (73 in) occurs between May and September. The aquifer of this city is primarily recharged by direct rainfall, river water, and floods through direct infiltration and percolation. But due to unplanned urbanization, the recharge area of the city is decreasing significantly with time. It is observed that the water level is declining at the rate of about 2 to 3 m per year depending on the location. The vulnerable conditions of the aquifer may result in the drying of existing wells, land subsidence, and intrusion of contaminated water from adjacent polluted rivers. Covering the vertical recharge inlets with pavement materials or other construction materials causes water logging for even small duration heavy rainfall in most areas of Dhaka City. An inadequate storm water sewer infrastructure and improper maintenance of the storm sewer system further aggravate the scale of this problem.

 

Fig02
Figure 2: Present and future water demand scenario in Dhaka City

 

Fig03
Figure 3: Source wise water production per day in Dhaka City