Tuesday, November 20, 2018 | ePaper

Decaying rivers and water crisis

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Contd from page 34 :
Salinity in the rivers appears to be a most threatening issue following absence of sweet water. India should be liberal to the cause of Bangladesh, in sharing water resources and upholding the water treaty which was signed by both the countries.  Let good sense prevail.     
The Padma - Gorai and the south-west region dilemma
The Padma- Gorai rivers are the important source of fresh water supply to the southwest region of Bangladesh and the Gorai is the only remaining major spill channel of the Ganges river flowing through this region. The dry season flow of the Padma has decreased largely since the commissioning of the Farakka Barrage in West Bengal, India in 1975. For the last 30 years the dry season monthly mean flow (November- May) in the Gorai River has been decreasing and has reached a minimum value of 526m/sec. Not just the dry season flow, the wet season flow is also declining. However, at the plan form conditions in the Ganges-Padma river between the Hardinge Bridge and the Gorai off-take developed unfavorable alignments. Erosion along the Ganges-Padma river bank due to high flood in combination with the hard point at Talbaria causes the off-take of Gorai located at the inner bend to catch more sediment deposited at or near the off-take area. The siltation and reduced flow in the Ganges-Padma together yield low flow in the Gorai river.  And from 1988, there has been a resultant hastening of the natural decline of the Gorai river as it becomes totally cut- off from the Ganges- Padma during dry seasons. Closure of the Gorai during the dry season, not only deprives the SWR of its most important source of fresh water supply but also it has resulted in a number of environmental and social and economic impacts. According to a study, a number of hydro-morphological and environmental impacts have been recognized in the Gorai catchment. These include , a northward penetration of salinity, sedimentation of rivers, deterioration in the quantity and quality of ground water, reduced surface water availability, reduced irrigation opportunity, reduction in navigation services, impacts on domestic water, reduced crop and fish production, declining bio-diversity in the riparian zone, the Sundarban forest and associated migratory species. The impact of this hydro-morphological change of the Ganges-Padma and the Gorai river system is very serious in terms of increased salt water intrusion in the coastal area around Khulna and the Sunderbans. A marked impact has also been observed in the ecological   functioning of the Sunderbans Mangrove system with the increasing rates of change in vegetation composition with associated reduction in sustainable harvest levels. The environmental impacts thus include the salinity intrusion via the tidal river systems, increased salinity within the Sunderban Reserve Forest, reduced in stream flows affecting navigation, ground water recharge and surface water availability. According to a number of studies, the Gorai carried around 15% of the Padma (the Ganges) flow before the commissioning of the Farakka Barrage and the flow of the Gorai was reduced to two thirds of it when the Barrage was set to work. Despite achieving greater flows in the Padma through a water sharing agreement between Bangladesh and India in 1996, the flow going into the Gorai ceased altogether due to heavy siltation of the river's off-take. This came about because the flows in the Padma had become increasingly less able to carry the natural load of sediment much beyond the point of the Gorai off-take and it was deposited as a continuous sandbank. The flow in the Padma, during wet season, however, is more than sufficient to keep a wide channel open and the Gorai flows freely. Under the current trend , there is a possibility that the buildup of the deposited sand  and silt would be such as eventually block the Gorai permanently even in the wet season as has occurred with some of the rivers further to the west. A recent study suggests that approximately 50 million people of the fourteen districts of southwestern districts including greater Kushtia, Faridpur, Jessore and Khulna districts that depend on the Gorai river directly and indirectly would face a colossal social and economic damage and environmental degradation following unusual and unprecedented reduction of fresh water supply to the Gorai river that takes different names at different places when it meets the sea. The southwest districts of Bangladesh are subject to tides from the Bay of Bengal twice a day. The tides bring saline water which travels along the rivers and creeks and overflowing into adjacent lands damages them with salt deposits. The intrusion of salinity inland is checked by the upland flows coming down the rivers especially during the low water months. A study revealed that with the decrease of upland discharge through the Ganges-Padma, the Gorai, the Madhumoti, the Ariel Khan and the lower Meghna rivers salinity will penetrate further inland towards Jessore, Faridpur and Kushtia districts where water is now fresh for most of the years due to the flushing effects of the tidal rivers by upland discharge through the above rivers. With the decrease in fresh water discharge through the southern rivers the intrusion of salinity is increasing rapidly. An area of more than 5000 square miles was under the influence of salinity. This has increased to a great extent and the salinity has now intruded as far inland as the Madhumoti and the Gorai. According to reports available, the concentration of salinity in Khulna areas has increased by 4000 percent and has penetrated into the main land. Besides, a number of industries including the Goalpara Tharmal Station and the Newsprint Mills faced closure. The effects of salinity and lowering of the water level underground have seriously threatened the vegetative growth in the areas served by the Padma that carried about 55,000 cusecs of water during the most critical days prior to the unilateral withdrawal of water by India.
The  Ganges (the Padma) and its off-shoot, the Gorai river, pass through Kushtia, a western district of Bangladesh. The Gorai which originates from the Ganges (the Padma) goes almost out of water during the dry season as the mouth of the river Gorai is almost closed following heavy siltation. As a result, no water from the Ganges could enter into the Gorai. The flow of water thus has been stopped and no sweet water could pass through the Gorai to the southern rivers.  
As stated earlier, the Gorai is an off-shoot of the Ganges (the Padma in Bangladesh) and it originates from the Ganges at Talbaria (Kushtia) around 2 km from the Hardinge Railway Bridge, Paksey. It passes by the side of Kushtia town and the two upazila, Kumerkhali and Khoksha and takes the name of Madhumoti, at Kamarkhali, Faridpur and finally joins the Bhairab at Khulna and then falls in the Bay of Bengal. The Gorai and the Bhairab are the two rivers that continued to supply fresh water to the southwest region of Bangladesh. The Gorai has been the largest perennial distributaries of the Ganges, supporting fresh water to the 50 million people of at least twelve districts of the southwest region for hundreds of years. This fresh water flow is crucial to the maintenance of an ecological balance in the region, particularly in the checking of salinity intrusion. The dry season flow of the Ganges has decreased greatly since the commissioning of the Farakka Barrage in India and from 1988 there has been 'a resultant hastening' of  natural decline of the Gorai river so much so that the mouth of the Gorai is totally cut off from the Ganges during dry season following heavy siltation. The closure of the Gorai off-take during the dry season has resulted in a number of hydro-morphological, environmental, social, economic and cultural impacts. These include a northward penetration of surface water salinity, increase in soil and ground water salinity, sedimentation of rivers, deterioration in the quantity and quality of groundwater, reduction in surface  water availability, curtailment of irrigation opportunity, adverse impact on domestic water supply, reduction in crop and fish production, deterioration of occupational and employment opportunities, negative consequences for health and nutrition of the common people, reduction in navigation services, problems of water use by industries, declining bio-diversity in the riparian zone and a very negative impact on the Sundarbans, the biggest mangrove forest of Bangladesh. The impact of this hydro-morphological change of the Ganges and The Gorai river system is quite significant in checking the salt water intrusion in the coastal area around Khulna, Satkhira and Bagerhat districts and the Sundarbans.
Water crisis threatens the Sundarbans and the wild life
The southern region of Bangladesh is bound by the Sundarbans that supports extensive bio-diversity. It is the habitat of the largest contiguous population of the Royal Bengal Tigers and a number of endangered species. The mangrove system that supports aforesaid resources relies heavily upon the freshwater supply from the distributor rivers of the Ganges. The condition of the Sundarbans reserve forest has been threatened with the passage of time and this has caused serious negative impact for the relevant life supporting system in the region. Experts are of the opinion that the stoppage of fresh water supply to the region is having disastrous consequence not only on the total environment and social imbalance in the SWR of Bangladesh but also on the life and living condition of the people belonging to 14 districts.
The experts further hold that the Sundarbans mangrove ecosystem is increasingly exposed to various types pollution. Intensive agricultural activity in the upstream has greatly with the accompanied increase of insecticides, fungicide and fertilizer. Intensive and indiscriminate use of these potential toxic chemicals in the agricultural field are untimely carried to the Sundarbans downstream  through the rivers.Khulna city has a number of industries located in Rupsa, Khalishpur and Shiromony. These industries discharge more than several thousand  waste water in the river which are ultimately carried  to the Sundarbans through Bhairab- Rupsa system. There had been considerable sedimentation that results in the formation of 'Chars' in the rivers of Possur and Shibsha in recent times. Decreasing flow in the Gorai has been attributed to cause sedimentation.       Contd on page 37

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