South Asia And Kosi River
By DR AB Thapa
We are now at a very critical juncture. Our country will soon have to take crucial decisions on the issue of the Kosi problems. Nepal would be needing the cooperation of its neighbours also in finding optimum solution to Kosi problems which involves the harnessing of the vast potential of this river for generating cheap electricity, developing inland waterway, irrigating vast tracts of cultivated lands to increase agricultural productivity, and above all for saving the life and property of millions of peoples living in our region from a new series of devastating Kosi floods. All these issues directly concern our country. Thus it is quite evident that we are now forced to make a choice between development and destruction on taking decisions on Kosi problems.
Past Sufferings of Nepalese
The Kosi river known as the river of sorrow of the Bihar shifted from east to west over 12O km in the last 200 year. In the past about 10,000 sq. km. of lands had been laid waste as a result of the sand deposit. In course of shifting, many towns and villages were wiped out, and heavy losses of property, cattle, and human life were inflicted. Fortunately the embankments built few decades ago temporarily helped to check the lateral shifting of the Kosi.
All the elderly people living in the Saptari district of our country not far away from the Kosi river would not have much difficulty to recall that some 50 years ago the channel of the Kosi river flowing across the Sunsari district from north to south was gradually shifting laterally from east to the west. The river was already quite close to Hanumannagar. It is reported that by that time the Kosi. River debouching into the Terai plain at Chatra and joining the Ganges River near Kursella in India had already laid waste about 500 square miles of lands in Nepal alone. People living in the eastern part of the Saptari district were panic stricken. They were leaving their ancestral homes in thousands to find shelter at safe places far away from their villages carrying with them whatever few things they could take with them. The headquarter of the Saptari district at Hanumannagar was swiftly moved to Rajbirag which was at a safe distance away from the Kosi River. Fortunately the shifting of the Kosi River course to the west was held in check by the embankments built on either side of the river some 50 years ago. Now all those who are involved in the Kosi River study are saying that the embankments built to protect the life and property of millions in India and Nepal might have already outlived their usefulness. What is going to happen the next? Every common man would be expecting to get an answer. In this connection it is important to know why the Kosi River changes its course.
Rise in Kosi River Bed Level
The Kosi River brings every year an enormous quantity of sediments from its catchments in the mountains. Sir Claude Inglis an expert on Kosi had attributed the shift of the Kosi River channel to excessive sand load carried by the river. Leopold and Maddock considering Kosi behavior had stated that a braided stream will tend to shift laterally at a rate dependent on the rate of accumulation of material being deposited. As one course becomes higher than possible adjacent paths, the river would shift.
Data published in the American Society of Civil Engineering in March, 1966 indicate that in the period between 1938 and 1957 every year on an average about 100 million cubic meters of sediments used to be deposited on the Kosi River bed. The maximum such deposition was around Nirmali in India not far away from Hanumannagar. There was very big change in sediment deposition pattern immediately after the completion of the Kosi barrage in 1963. The results of the Kosi River channel study for post barrage period have been published by V.C. Galgali, Central Water and Power Research Station, Pune (India), and Gohain & Prakash of Roorke University. All the past studies confirm that the Kosi River bed just upstream of the barrage has significantly aggraded due to sediment deposition. On account of ponding, sediment deposition had occurred, flattening the bed gradient. The bed slope of the river in the pond area was abut 0.61 m per km in the year 1956 prior to construction of the barrage, which became flatter to about 0.42 m per km in the year 1969, ie in six years of the functioning of the barrage. Studies were made to determine the sediment deposition based on post flood 1963 and 1970 surveys These studies indicated that about 35 million cu.m. sediments had deposited in the pond length of about 10 km upstream of the barrage, giving an average depth of about 0.4 m in about 8 years with a rate of bed level rise at about 0.05 m per annum.
Alarming Situation
Few years after the commissioning of the Kosi barrage there was a big flood in 1968. A discharge of about 25,000 cumecs was recorded. The flood at that time did not pose any serious threat. At present the conditions might be altogether different. It is said that whenever the discharge exceeds 9,000 cumecs which is fairly common the whole area between the embankments is submerged. Such observations raise the fear that a flood similar to 1968 flood in magnitude could prove to be catastrophic. It should be further remembered that the 1968 Kosi flood is not exceptionally rare. A flood of this magnitude has already been observed twice within the last 50 years. Fortunately in course of the last 36 years the maximum flood discharge of the Kosi River has not exceeded 16,000 cumecs.
Lack of Awareness
According to the prediction of renowned experts like Sir Claude Inglis the Kosi river is now on the verge of shifting to the east far away from its present course. The peoples of Nepal and India are heading for a natural disaster of an unprecedented scale. But hardly anyone in Nepal appears to be concerned. Even the institutions like the ICIMOD noted for their role in studies of the environmental problems and water resources of Nepal have not yet realized the extent of this danger. There is absolutely no mention about it in the recently prepared water resources strategy report that has led great emphasis on water induced disaster mitigation. It would be unfortunate if the Kosi swing to the east takes the life and property of millions in South Asia by surprise while the concerned government agencies and various relevant international institutions operating in Nepal would merely be silent spectator.
Sorrow of South Asia
If the Kosi River changed it course to the east, the flood-affected area of the Kosi in the past estimated at about 10,000 sq. km could again be laid bare with sand deposits within a certain period by the combined effect of the Kosi floods that bring huge quantity of sediments and the shifting of the main river course from one channel to another. The changing of the river course is the distinguishing feature of breaded rivers like the Kosi.
The Kosi was known as the river of sorrow of Bihar in the past. Kosi would again abandon its present course triggering off a new cycle of damages and destruction if we failed to control this river in time. After such incident the Kosi might not anymore be only the sorrow of Bihar. It could equally be the sorrow of the West Bengal and Bangladesh apart from the terrible havoc the Kosi floods would be playing with the safety of people in south-eastern Nepal. Economy of much of the Eastern India could be badly affected. Very large stretch of Indian railways and highways could be completely wiped out by unexpected change of the Kosi river course. As a result, north-eastern provinces of India would be cut off from the rest of that country.
Resolution of Kosi Flood Problem
Provision of dams in the drainage area with very big storage volume is the only lasting solution to the Kosi flood problem. It is the opinion of the renowned experts and scientists involved on the Kosi study in the past. We can draw such lesson from the past experience of China also. It can be concluded that there are not any substitutes for the large storage dams to control the Kosi floods. The storage dams should be provided in time. Unfortunately some peoples in Nepal and India have misgivings about the Kosi dams. Such misgivings are unfounded and they are often the result of present global disenchantment with the high dams particularly for the generation of hydroelectricity. In case of the Kosi dams this type of notion is completely misplaced. It need not be explained that the life and property of too many peoples in Nepal and India would be at great risk if the Kosi dams are not built in time.
Immediate Intervention
The imminent danger of the Kosi floods to be triggered off by the sudden change of its course is too great to be ignored. Tens of thousands of people in Biratnagar area might perish and many times more could be rendered homeless. People in far greater number would be affected in north-east Bihar also. Luckily, the implementation of the relatively small Sun-Kosi Storage Dam Project at the earliest could provide effective shield from the threat of the Kosi floods for about next 40 to 50 years. If future studies confirmed that there is room for doubt about the capacity of the Sun-Kosi Storage Reservoir alone to control the Kosi floods, we could also think of implementing the small Tamar-1 Storage Dam Project side by side with the Sun-Kosi Dam Project. Thus, we need not rush to implement in very near future the mammoth Kosi Dam Project which has been considered to be indispensable for the safety of life and property of millions in our region.
The Kosi Dam Project is expected to be perhaps the largest in the whole world in terms of the height of the dam and the total installed capacity of the power station if this project is to be planned to accrue benefits to Nepal to the desired extent. We should beware of unintentional give-away in Kosi development. The optimum Kosi development should not be compromised. A less than optimum dam could preclude optimum development of the Kosi Dam Project for all time. As a result, it is going to take a very long time even to complete the detailed study of such a giant Kosi Dam Project. No wonder it took China more than 20 years just to complete the detailed study of the Three Gorges Project which can be considered to be more or less on a par with the proposed Kosi Dam Project in size and also in volume of investment.
The 1997 Indo-Nepal Study Agreement
In 1997 an agreement was signed between Nepal and India to carry out feasibility studies of the Sun-Kosi project and the Kosi project along with a navigation canal linking Nepal with the seaport. This agreement is a substantial modification to the earlier understanding reached between the prime ministers of Nepal and India that covered only the Kosi high dam. There is a very close interrelationship between the Sun-Kosi and the Kosi projects. This interrelationship required the inclusion of the Sun-Kosi dam project in the Kosi development. Even a simple analysis of both these projects clearly illustrates the following points that help to explain why the Sun-Kosi project should be built first, and as a result, the feasibility study of the Sun-Kosi Project had to be completed as soon as possible.
(a) The diversion of the Sun-Kosi river at Kurule is the most important project of Nepal for agriculture development in near future. This very important project for Nepal would be precluded for ever after the completion of the construction of the Kosi high dam project. Fortunately the Kosi high dam project can be built even after the completion of the construction of the Sun-Kosi high dam project.
(b) The Kosi high dam along with a navigation canal to link Nepal with seaport is a very big project. It will take very long time to implement this project. But the Kosi river is on the verge of shifting to the east. The Sun-Kosi dam project could control the Kosi floods in the interim period till the Kosi high dam is completed.
In Conclusion
Mr. F.A. Shilling Feld, a renowned expert on Kosi study, had made a chilling forecast a long time ago “ The westward movement of the Kosi oscillation (in the past) is slow and is in a series of steps, each of which is attended with damage to property of temporary nature. The eastward movement (in future) of the oscillation will probably be accompanied with great loss of life and property.” It is hoped that we all will be taking up the Kosi problems very seriously.
(Dr. Thapa writes on water issues.)
