West Bengal rivers
Bengal is proverbially a land of rivers. Despite the fact that the drainage map of West Bengal has changed appreciably during the known historical period and that many rivers have changed courses and some have even disappeared from the surface or gone dry, our understanding of the dynamics of river system is inadequate. River management in West Bengal has been almost completely guided by the colonial legacy of embanking rivers, as well as by the simplistic engineering approach of dam-building.
The enduring myth that freedom from floods can ever actually be achieved demonstrates a dramatic lack of understanding of how river basins function in the sub-continent. In contrast, farmers in Bengal had an age old culture of living with floods. They had long understood that the floods were in many ways blessings in disguise. Indeed, farmers welcomed low-intensity flooding, having inherited a uniquely evolved technique of replenishing their farmland with layers of fertilizing silt carried by the water--a method called ‘overflow irrigation’.
Despite having functioned well for centuries, such traditions began to disappear during the British Raj. At that point, many rivers in Bengal were embanked in an attempt to combat the annual flooding, including the Damodar. These embankments did ensure security against low-intensity flooding, but the long-term effects were detrimental, leading to the decay of river systems and congestion of drainages. The parallel embankments along both banks of rivers restricted the spill area and interrupted the sediment dispersal on the floodplains posing a great threat to the agrarian economy of Bengal. The areas trapped within the embankments were gradually elevated by the deposition of sediment load while the adjoining parts of floodplains remained at the same height and thus aggravated the decay of channels.
The situation deteriorated further during the mid-18th century, when the colonial rulers dreamt of binding India by iron chains with the aim of better mobility of security forces and to transport Indian cotton for English textile mills. The road and rail-focused urban/industrial model of development was imposed on an inappropriate geographical setting, leading to a spectrum of environmental changes. The roads and railways were outfitted with inadequate culverts, which inevitably intercepted crucial drainage points. In turn, this led to an expansion of floodable areas, outbreaks of malaria from mosquitoes that bred in the stagnant water, and a general decline in crop production in the impacted lands.
After the British Raj ended, massive engineering structures have been built over the years across the Ganga, Teesta, Damodar, Mayurakshi and Kansai but the farmers relied more on groundwater pool to ensure irrigation, and its over exploitation has reduced the base flow into the rivers during lean months.
The engineering structures obviously rendered some benefits to society but continued to imperil the ecological security and delicate hydrological balance of the densely populated lower Ganga plain. In the course of the past six decades, this has led to the loss of livelihoods for many poor, rural families. In West Bengal, official documents state that erosion has increased since the Farakka Barrage was completed in 1975, rendering at least half a million people homeless.
Introduction by Prof Ramaswamy Iyer
Lecture by Dr. Kalyan Rudra on "Rivers of West Bengal"
In the absence of a firm understanding of the geomorphologic processes at work in the Ganga-Brahmaputra delta, the flooding in this area continues to be labeled a ‘disaster’, one that needs to be ‘controlled’ by structural measures. What needs to be understood is that, with 80 percent of the annual flow coming during the monsoon months, the discharge in the tropical rivers is temporally skewed and cannot be accommodated within the shallow cross-sectional areas of the riverbed in the plains. When the river enters the plains, the slope suddenly declines causing the sediment load to be dropped on the bed, making it shallow and wide. The artificial reduction of the cross-sectional area only causes increasing vulnerability.
Planners, still guided by the old, flawed logic that the flood can be controlled by structural measures, steadfastly deny the lessons of the past: that no engineering marvel can keep the massive monsoon discharge within the shallow confines between man-made embankments. One way or another, the silt-laden flood waters have to be allowed to spill out.
Such an undertaking in the lower Damodar plain would need some engineering interventions in order to connect the ‘beheaded’ distributaries with the main channel, as well as to establish flow regulators at the off-take points, the proposed points of connection between the old channels and the present main channel. The selective dredging of some stretches of the old channels would ensure quick outlets for floodwater.
The benefits from such a project are there for all to see. Utilising the old channels would be less expensive and provide a more realistic solution to the recurrent ‘disasters’. Sadly, there is no sign that the officials involved in interventions with river systems will move away from simplistic engineering to less intrusive, more effective methods of management. Water managers in West Bengal continue to deny the holistic eco-hydrology of the river basin, and instead try to solve the problem from a narrow, sector-based outlook.
Mahanadi: Common property, uncommon interests
In real terms we can say that the Mahanadi is the only major river of the country that has been completely privatised. The issue of privatisation thus goes beyond the Seonath (Shivnath) and makes the river a hotbed of exploitation by private interests. Even as the river's health is impoverished, the people at the helm of affairs cut it down to a small water body by talking about it in bits and pieces.
Lecture by Ranjan K Panda on Mahanadi river
There is nothing called an upstream or downstream problem in the Mahanadi any longer. With a plant every five or seven kilometers, the river in upstream Chhattisgarh is already exploited, and downstream Orissa the Mahanadi now provides the maximum water to industries compared to the other ten river basins in the state. It is a river entirely for private use.
This makes the river most contentious. Because of the abundant and easily accessible water available now and no clarity on its uses, disputes over rivers have stopped any new thinking on uses. So the issue of the Mahanadi has all the makings of a case from which to learn and re-learn water management in rivers.
The river is the only one left, that will sustain close to India’s thirty percent power production and many more industrial investments. Even as both states compete to kill the river, there is no common thought on its management. The presentation gave an overview of the present state of affairs taking into consideration the uses and abuses of the river and the resultant decay in its health. It also tried to bring into perspective the overall river management issue in the light of recent judgements and decisions of importance.
Indus river system under threat: The case study of the Jhelum basin
The Indus river is one of the major rivers of the world that drains one of Asia’s chief catchment basins, and has been the locus of some of the earliest known human civilisations. The catchment area, with varied topography, climate and land cover, is spread over an area of about 3,99,000 sq km. All over the basin tremendous changes in the land system, cryosphere, climate, demography and industrialisation have brought about adverse impacts on the ecology and health of the river system.
This talk focuses on these changes observed in the Jhelum basin that have occurred over the last four decades with consequent changes in the ecological health of the basin. It is believed that these changes and impacts in the Jhelum are broadly representative of the other four catchments of the Indus basin.
Snow and glacier melt runoff continuously feed the rivers and water bodies in the basin, thus making them perennial. Recently, the Jhelum basin has been witnessing drastic decrease in snowfall. This reduction together with the receding glaciers has resulted in reduced water availability. Long term viability of any existing and potential developmental schemes in the fields of irrigation, agriculture, horticulture, hydropower, tourism and drinking water supplies is intimately dependent to the snow, glacier and water resources. Kolhoi, the main source of drinking water and irrigation in the Jhelum basin, has lost 18 percent of the glacier area during the same period.
15 of the last 20 years have been the hottest since the recording of temperatures started in 1850. The analysis of the vast repository of meteorological data for Mean Annual Temperature from 1893 up to 2009 in Jhelum shows a statistically significant increasing trend. Both mean minimum and maximum temperatures are also showing an increasing trend during the observation period. For the last 100 years, the mean minimum temperature of Srinagar has increased by 1 degree centigrade.
Lecture by Prof. Shakil Romshoo on Indus river system
While as the mean minimum temperature of Srinagar has increased by 1 degree centigrade, the mean minimum temperature of Srinagar for winter and summer has increased by 1.2 and 0.2 centigrade respectively. The average annual temperature has also increased by about 0.8 degree centigrade. For winter, the annual increase in temperature recorded at Srinagar is 1.1 and for the summer, there is an observed increase in temperature 0.2 degree centigrade.
Similarly, the mean maximum temperature has increased by 1.3 and 1 degree centigrade respectively. Compared to the global temperature trends, the Kashmir Himalayas are showing higher rates of temperature increase for both winter and summer season. Just to mention here that our weather system is very much controlled by the north westerlies originating from the mid and higher latitudes in the northern hemisphere.
We have observed decreasing precipitation trends particularly snow over the Jhelum region by observing the data and model simulations. From the analysis of the precipitation data for the last 100 years, it is evident that both snow and liquid precipitation are showing decreasing trends all over the region. As the precipitation in Kashmir is predominantly in the form of snow, the snow and glaciers determines the availability of water resources for societal needs in summer and spring seasons.
Looking at the snow depletion curves developed over the basin, the decreasing trends in the snow cover distribution are quite discernible all over the Pir Panjal and the Himalayan ranges. The decreasing trend in the snow cover and the increasing trends in the winter and summer temperatures observed over the area has serious ecological and economic consequences for this mountainous state.
As a result of scanty and erratic snowfall, most of the tributaries of the Jhelum are showing lower discharge and will, therefore, affect livelihoods at both local and regional scale through effects on agriculture and energy production. Reduction in the discharge of rivers flowing out from the Kashmir Himalayas could have serious implications for the political stability of the entire South Asian region in the long run and should be a cause for serious political stability of the entire South Asian region in the long run and should be the cause for serious concern to all of us.
The data shows that the frequency of flooding has increased in the valley during the last few decades. Coupled with the unplanned urbanisation and mismanagement of the Jhelum floodplains, the situation is going to be alarming in the near future. One can well imagine the future scenario, with most of the wetlands that used to act as sponge during flooding being urbanised and converted into concrete landscape.
Though we have been fortunate that the valley has not been recently hit by an extreme weather event, with increasing temperatures and discharge in the rivers, an extreme rainfall event of the size observed in Mumbai (2005) and Bihar (2008) and Karnataka (2009), shall result in one of the worst floods in the history of Kashmir and may unleash havoc in the floodplains.
Most of our water bodies are already fighting a losing battle for their survival. Wetland habitat, productivity and process being linked to the hydrological cycle, are getting adversely affected due to seasonal changes in the precipitation, reckless urbanisation and large scale changes in the land system. Most of the wetlands have less biodiversity in terms of fauna and flora compared to the situation, say only 50 years ago. In the process, obnoxious weeds and other aquatic life have succeeded the more productive and useful biota. A number of wetlands we are monitoring for the last forty years are showing a remarkable shrinking in their extent and water spread.
In the entire Indus basin, we do not have any coordinated and established practice of data observations on any of the natural resources, whether it is water, soil, forests, glaciers, agriculture, meteorology, geology or other related disciplines. Mountaineous regions require much greater density of observations than the neighboring flat lands to achieve same reliability of areal estimates.
It should be a matter of concern to all of us that the state lacks a long historical time series of hydrometeorological observations. The opportunity to observe such variables in the past has been lost forever. At least now, we should rise to the occasion and build, on priority, an adequate network of observations for environmental variables related to primary processes of atmosphere, land, water, snow etc.,throughout the state. The aim should be to deliver a functioning system for distribution of data and information resulting from these observations.
In the Indus basin, we need to address such questions as to how is the river ecology changing? How does the riparian environment respond to the natural and human induced changes? What are the consequences for people? The answer to these questions would facilitate the solution of our environmental problems. But the answer would not come in vacuum. We would have to utilise all the available tools employing scientific methods to look for the answer. If we understand the processes leading to the ecological changes occurring in the Indus river system, we can help ourselves to mitigate the effects through improved planning, improved response and more efficient strategy. We are always in a hurry to suggest and execute remedial measures (having been tested in a different environmental setup), without first thoroughly researching and understanding the problems for working out alternative and befitting solutions. This needs to be done away with.
Playlist: Rivers of West Bengal, Orissa and the Indus system
The lecture in various parts can be viewed at Youtube here
Related content
The lectures in the series can be viewed here:
- Introduction: 'Everything you wanted to know about rivers in India', a compilation of all talks
- 1st lecture: 'River Ganga', by Rama Rauta and K C Sivaramakrishnan
- 2nd lecture: 'River Yamuna' by Prof. Brij Gopal & Manoj Misra
- 3rd lecture: 'River systems of Bihar:Kosi and Bagmati' by Dr. Dinesh Mishra
- 4th lecture: 'Rivers of the North East' by Dr. Chandan Mahanta
- 5th lecture: 'Bagmati river in Nepal' by Dr. Ajaya Dixit and Dr. Dipak Gyawali
- 6th lecture: 'Rivers in Western Ghats of India' by Parineeta Dandekar and Pandurang Hegde
- 7th lecture: 'Rivers of Tamil Nadu and Kerala' by Prof. S Janakarajan and A Latha
- 8th lecture: 'Stuffed rivers of Vrishabhavathi-Arkavathi' by Leo Saldanha and Bhargavi Rao
- 9th lecture:'Rivers of Gujarat' by Himanshu Thakkar
- 10th lecture: 'Rivers of Andhra Pradesh' by Dr. Uma Maheshwari
- 11th lecture: 'Rivers of West Bengal, Orissa and the Indus system' by Dr. Kalyan Rudra, Mr. Ranjan Panda and Prof. Shakil Romshoo
India Water Portal is grateful to Prof. Ramaswamy Iyer and the India International Centre for allowing it to record the lecture and share the videos online.