Bringing dying rivers back to life

Bangladesh is a riverine country with about 700 rivers and their tributaries washing its shores. The economy of the country has predominantly been agricultural because of the rivers. Apart from constituting the economic backbone of the country and presenting the beautiful geomorphic features, these rivers have been contributing enormously towards agriculture, waterway communication, and energy source among others. Our culture is also deeply indebted to these rivers. Most major rivers owe their origins elsewhere and after flowing through other countries they empty themselves into the Bay of Bengal in Bangladesh.
Bangladesh has four major river systems - (1) the Brahmaputra-Jamuna, (2) the Ganges-Padma, (3) the Surma-Meghna, and (4) the Chittagong Region river system. Brahmaputra is the 22nd longest (2,850 km) and the Ganges is the 30th longest (2,510 km) river in the world. The Brahmaputra is the longest river to pass through Bangladesh, covering a length of 1,802 miles, and also flowing through India, Bhutan, and China. Since these rivers contribute immensely to the economic growth of Bangladesh, it is vital that the rivers are left healthy and alive. 
The tragedy that has of late befallen is that the rivers which are treated as the life line of the country are drying and dying. Apart from external factors, the drying is being caused by internally developed phenomena as accumulated silts on the river beds and continuing pollutants and contaminants from different sources. Widespread encroachment of banks to develop land for various purposes and indiscriminate urbanization are two other main reasons.  
Mainly the small and medium sized ones are being filled up from bank-side. This not only affects the natural flow of rivers and canals, size of water bodies are also reduced in the process and navigability lost. In addition, rivers are prone to surface water pollution that arises from oil spillages from vehicles and nearby factories. 
Secondly, water is pumped out during the lean season from many rivers for irrigation. Although we get some paddy out of the process, the natural production of freshwater fish is destroyed. These rivers remain dry till April and May - the breeding period of fish. 
Therefore, fish migration/spawning is hindered. This happens to the beels and jheels as well. Many wetlands in Tangail, Sirajganj, Pabna, Faridpur, and Gopalganj, once rich habitats of aquatic life, are now devoid of fish. As a result of pumping out water from different rivers, almost one third of our rivers have already lost their year long navigability. 
Indiscriminate urbanization is also not helping the canals and other water bodies to play their economically desired roles. The hoof beats of 27 canals emerging from Buriganga are also gradually dying away. Sometimes the level of dissolved oxygen in Buriganga waters goes down to almost zero and ph standard indicating the oxidizing and alkaline level goes down abnormally low making survival difficult for fish and other aquatic animals. At times the power of conductivity of electricity of the water goes down to 50 per cent rendering rivers lifeless.
Almost all industrial units in Dhaka and adjoining areas have no waste treatment plants (ETP) of their own, industrial wastes like chromium, nitrate, lead and high level mercury are regularly disposed to river Buriganga. It is found that each litre of Buriganga water contains 0.48 mg of chromium which may even be a cause of death for animals living in its waters. According to Inland Water Transport Authority, 185 types of wastes are responsible for polluting the waters of four rivers flowing around Dhaka.  
Every day on an average 7,159 kg of industrial wastes are being dumped into Turag from the industrial units at Tongi. Not only that, unplanned growth of industries on the banks of Shitalakhya at Narayanganj and Karnaphuli at Chittagong causes huge industrial wastes to accumulate on the river beds. 
Untreated liquid industrial effluents are being discharged into rivers indiscriminately, especially around urban areas, leaving these rivers biologically dead as the level of dissolved oxygen goes down very low. Every river when it flows naturally, would have dissolved oxygen that helps fish and other aquatic animals to survive. 
In Buriganga, the dissolved oxygen level comes down to as low as zero in the dry season. When the level of pollution rises very high in Buriganga and Shitalakhya, the treatment of water (in order to turn it into drinking water) becomes very difficult. Furthermore, sulfur of gas cylinders and nitrogen compound are polluting the atmosphere of coastal areas.       
Encroachment on river banks by influential quarters is another cause of degradation of rivers. Such unlawful occupation of river banks has converted many free-flowing rivers into a series of stagnant water bodies. Rivers follow some rules of nature and if the width of a river is reduced by encroachment, natural flow may shrink in volume, as a result of which the depth of the river is reduced which leads to permanent shrinking of the river in terms of size and volume. If the river is a part of a network of streams, the flow will be diverted to some other channel and if it is unconnected to any network, floods will occur in case of slightly high rainfall. 
In a backdrop like this, there is very little option than restoration of the rivers whereas bringing the dying rivers back to life is of utmost importance. It is possible to do so through processes of 'river management' and building 'river training infrastructures' . 'River management' projects that include bank revetment and 'river training infrastructures' that include both in-channel structures ensure optimum river infrastructure management. Further, restoration through appropriate plans to dredge in appropriate reaches, can significantly increase the services provided by a healthy ecosystem, too often neglected by decision makers. 
Conversely, river restoration schemes may imply significant changes in water management and land use and hence may leave some negative economic impacts on certain economic activities. It may hamper navigation for agriculture for instance. In order to support river basin planning and river related policies, it is vitally important to assess these impacts with appropriate and transparent methods, and weigh them against the benefits foreseen. 
Apparently, the government plans to take up some major projects for dredging big rivers like the Jamuna. Over the last few years, huge funds have been spent on dredging the Jamuna near Sirajganj to very little effect. We should therefore first evaluate the success of such projects before embarking on any new major venture. Simply dredging does not ensure a long-term or sustainable solution. A river not only carries water; it also carries sediments. If a river carries a huge amount of sediment, dredging will not provide a durable solution, as incoming sediment in the following monsoons will fill up the dredged channel. 
However, if we go for well-designed 'river management' projects that include bank revetment, 'river training infrastructures' and dredging in appropriate reaches, we may find the right solutions. Again, this exercise should be carried out in phases so as to enable the 'observe and learn' approach. Dredging of small rivers, however, poses much less of a challenge. On the other hand, environmentalists suspect, due to prolonged existence of ship breaking yards, there may be serious long term impacts on the vast sea side and river bank areas. 
Bangladesh is among the few countries to have a separate court on environment. If a river is polluted or encroached upon, those affected by it should be able go to court seeking remedial measures. 
The governments of India and China are cleaning up their rivers; they are using modern technology such as Remote Sensing and Satellite Monitoring to monitor the conditions of the rivers. Developed countries are using proper monitoring mechanisms of maintaining the acceptable level of river water quality. Similar initiatives may be undertaken here.
To protect ourselves from pollution of river waters, we must prevent all solid, household and sanitary wastes including sewage disposal of WASA from mingling with one another. Construction of mills and factories on river banks should be avoided and safe disposal of wastes should be made mandatory. 
One hundred years ago, River Thames, the Clyde or the Rhine was in same condition as Buriganga is in today. But it was possible to clean the effluents and bring the rivers back to normal condition. We have the necessary laws, rules and regulations and capacity to enforce the same. If the government so desires, the Buriganga may be cleaned up in ten years. This time may be allowed to accommodate all remedial measures.
Last but not the least, raising public awareness is of utmost importance. People should be made aware of the significance of keeping the rivers free from pollution. If we make ourselves conscious and raise our voice for the right cause policymakers will eventually respond with technically sustainable solutions.
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