Dhaka and her rivers: A beautiful relationship gone sour
Dhaka city, established by the Mughals on the banks of the Buriganga, is surrounded by six rivers like a garland. There are Balu and Sitalakhya on the eastern side, Turag and Buriganga on the western side, Tongi Khal to the north and Dhaleshwari to the south. Tongi Khal connects both Turag and Balu rivers. Dhaleshwari and Sitalakhya join the south of Narayanganj and flow into the Meghna River.
These rivers receive water from the Jamuna (Brahmaputra river) in the wet season, and in the dry season upper reaches of these rivers are slowly replenished by the release of groundwater into the rivers. The lower reaches of the rivers are also influenced by the tidal variations travelling upstream from the Bay of Bengal. In the monsoon season, the river levels reach around 6.5m MSL (mean sea level) and drop to about 2.5m MSL in the dry season (Flood Forecasting and Warning Centre, Bangladesh Water Development Board). The maximum recorded level was around 8m MSL during the 1998 flood.
Once upon a time, these rivers were the lifeblood of the city carrying people, culture, trade and commerce. If we imagine the rivers as arteries, then the internal khals are the veins of Dhaka. Since the 1970s, the capital city of a newly born nation began to expand rapidly. The population and businesses grew, and by the 1980s, the arteries and veins started to become blocked and polluted. By the 1990s, some efforts were made to stop the deteriorating condition of the rivers by declaring some of them as Ecologically Critical Areas.
However, nothing changed, and in fact, things got worse. The rivers and khals continued to be encroached upon, and more wastewater from houses and industrial units poured into the rivers without any treatment, with several major sources of pollution being outside the city area—in Ashulia, Savar, Tongi and Gazipur. And today, in 2017, what we have of Dhaka can at best be described as a sick patient. You could say that her arteries and veins were filled with cholesterol, and she has diabetes, jaundice and many other diseases. She needs to be in the ICU for dialysis.
However, addressing the symptoms (treating the river water and preventing encroachment) can only be a short-term solution. We need to address Dhaka's underlying diseases to cure her properly. A megacity like Dhaka, home to around 15 million people and serving million others who come and go on a daily basis, requires proper infrastructure. Currently, there is only one sewage treatment plant—Pagla STP—which is not functioning at full capacity as the sewer system is faulty.
In 2012, Dhaka Wasa (DWASA) prepared a Sewerage Master Plan, which proposed a total of 11 STPs in and around the city. One of these is Dasherkandi STP, which will be built through Chinese funding and is expected to be operational by 2020. The other STPs are still in the conceptual or planning stage. These projects need to be fast-tracked and also the sewer network needs to be built urgently. Once these projects are implemented, the khals and rivers have a chance to recover. Industrial wastewater also needs to be treated through Effluent Treatment Plants.
Although some industries have built ETPs, they often do not operate the facilities fulltime. This practice needs to be carefully monitored. Also, more central ETPs are required in industrial estates. Finally, a massive, one-time river and khal cleaning project is required. The beds of these water bodies need to be dredged and the waste materials carefully disposed in specially built landfills. Then the waterfront areas around Dhaka can be utilised for recreation and public spaces. The khals and rivers can also be used for passenger transport around the city.
The drainage system of the city is also inadequate at the moment. The western part of the city is protected from river flooding by the Beribad (on the west) and DIT-Airport Road to the east. This part of the city suffers from flooding and water-logging due to heavy rainfall and drainage congestion.
Currently, there are only five pumping stations around the city: Goranchatbari (near Mirpur), Kallyanpur, Dholai Khal, Maniknagar (near Kamlapur) and Rampura. Temporary pumps are also used during the monsoon season to manage water-logging in localised areas adjacent to the flood embankments.
The eastern part of the city is still vulnerable to flooding caused by high water levels in Balu River. A flood embankment, with three pump stations, is currently being considered by Bangladesh Water Development Board (BWDB). Also, a four-lane road and rail line are being considered on this embankment. If urban development in eastern Dhaka is not planned and controlled properly, there is a real risk that the area will experience regular water-logging. Recently, DWASA has also prepared a Drainage Master Plan, which identified priority projects to recover and restore key khals in and around the city. Once these projects are implemented, the water-logging problem of the city will be significantly reduced.
Another key infrastructure system of this megacity is the water supply facilities. There are only four water treatment plants (WTPs), in Saidabad, Chandnighat, Godnail and Shonakanda. Only the Saidabad WTP, producing 450 million litres per day (MLD), can be considered for its contributions to meeting the huge water demand of about 2,500 MLD. The remaining water supply comes from over 600 deep tubewells (DTWs) scattered around the city. This is probably the largest groundwater well field in the world. The water table continues to decline on an annual basis due to over-pumping in and around the city.
DWASA's Water Supply Master Plan envisages reducing the reliance on groundwater by building more surface WTPs. However, due to the polluted conditions of the peripheral rivers around Dhaka, water is being sourced from the Padma and Meghna rivers. This clearly means additional costs to transfer the treated water to Dhaka. Already, the work for a 450-MLD treatment plant in Jashaldia (Munshiganj District) and a 500-MLD plant in Rupganj (Narayanganj District) are under way. These are expected to be operational by 2020-25. Further expansion of Saidabad (Phase 3, 450-MLD) is being planned by DWASA. With the shift to river water, pollution control measures need to be urgently put in place.
If we want to make Dhaka a more liveable city, both for us and our next generation, then we have to repair the damage caused to Dhaka's rivers. With strong political will supported by sound technical knowledge and public awareness, we can achieve this.
Asif M Zaman is Managing Director, Esolve International, and a part-time faculty member at the Department of Civil and Environmental Engineering of North South University.
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