Home Stories

Brahmaputra: Understanding the rage of the river through 700 years of water discharge history

“Records of streamflow, an important indicator of flood hazard, go back less than 70 years in Bangladesh and north-eastern India,” says Dr Mukund Palat Rao of Columbia University who along with colleagues, recently did a study that brought together observations from tree ring patterns with climate model projections to build a 700-year history of water discharge from the Brahmaputra river.

By Ajai Narendran
New Update

publive-image Brahmaputra river | Photo courtesy: @narendramodi | Twitter

“He no longer saw the face of his friend; instead, he saw other faces, many, a long sequence, a flowing river of faces, of hundreds, of thousands, which all came and disappeared, and yet all seemed to be there simultaneously, which all constantly changed and renewed themselves. He saw the face of a fish, a carp, with an infinitely painfully opened mouth, the face of a dying fish, with fading eyes - he saw the face of a new-born child, red and full of wrinkles, distorted from crying - he saw the face of a murderer, he saw him plunging a knife into the body of another person - he saw, in the same second, this criminal in bondage, kneeling and his head being chopped off by the executioner with one blow of his sword - corpses stretched out, motionless, cold, void - he saw the heads of animals, of boars, of crocodiles, of elephants, of bulls, of birds - he saw gods - he saw all of these figures and faces in a thousand relationships with one another, each one helping the other, loving it, hating it, destroying it, giving re-birth to it, each one was a will to die, a passionately painful confession of transitoriness…”
Hermann Hesse’s “Siddhartha”

This touching passage is one of the finest metaphorical expressions of a river that reflects life in its multifarious manifestations. Rivers anywhere are lifelines of the place and the people, and when it comes to the river Brahmaputra, it assumes a far greater significance because of its origins and the landscapes it flows through.

The Probe’s Ajai Narendran speaks to Dr Mukund Palat Rao. Dr Rao is an eco-climatologist, working as the Climate & Global Change Fellow at the National Oceanic and Atmospheric Administration (NOAA, US Department of Commerce) in Davis, California. He received his PhD in 2020 from Columbia University. His research paper on flooding in the Brahmaputra and Indus rivers in South Asia has been published in Nature.

With its antecedents traced to the Manasarovar lake region around Mount Kailash, the mighty trans-boundary river Brahmaputra is the ninth largest river in the world by discharge, and the 15th longest flowing through southern Tibet, then into Arunachal Pradesh and Assam (as the Brahmaputra) and flowing further south into Bangladesh as the Jamuna merging with the Ganga in the Ganges Delta and finally into the Bay of Bengal. The Brahmaputra is that imposing river that is not only the lifeline that nourishes and sustains the land and life across the borders but also a river that has carved itself into people’s psyche. Brahmaputra is a river of immense bearing on people’s lives that depend on it. But, seeing the plight of people year after year, the disconcerting question that emerges is whether we are doing enough in terms of preparedness and mitigation of the flood situation.

publive-image Flood situation in Silchar, Assam | Pic courtesy: @toramatix

The Brahmaputra, because of its unique geographical setting, exhibits cyclical hostile behaviour. The melting of the Himalayan snow results in a surge in floods. This means that there is no respite from floods even in summer, and during monsoon, floods are a common occurrence, and it aggravates between June and October. But, of late, much of what is man-made and the effects of climate change seems to have dramatically affected the Brahmaputra river resulting in floods of massive scale, leading to heavy loss of life, land and resources.

Despite the flood control measures taken by the water resource department and the Brahmaputra Board, the flood problem remains unsolved. While the conventional approaches and methods fail to resolve the issue, it is clear that the time has come to look into the problem from newer perspectives.

Recent science and research and the need to take a serious look at the findings are all the more pressing because the Brahmaputra river is the very source of sustenance for millions in India and Bangladesh. While massive floods continue to push the situation towards the tipping point, the routine annual normal flood also brings moisture and fresh sediments - much needed for agriculture and aqua farming. The fish caught during the flood season meet the protein needs of the rural population.

“In Guwahati, the condition is slightly better, but not in all areas. Silchar town is under water. The situation in some regions has somewhat improved, but the overall condition remains grim. The worst situation as on date is in Barak valley,” says Rajeev Bhattacharyya, a senior journalist who has been closely following the flood situation for over two decades now.

What is needed is a coordinated effort between the government bodies and the public that can include people also in the rescue, rehabilitation and rebuilding operations. Tapan Bhuyan, a trader based in Guwahati, says, “In the outskirts of Guwahati, many people are affected. In Guwahati, many streets are broken, potholes have come up, and repair work is going on. But I feel that repair works must be done immediately when roads are affected and not wait to fix it till it is badly damaged. This way, one could cut avoidable expenses. Water logging has receded in the city. Relief work is underway by the government agencies and NGOs. I don’t think the help provided by the administration is adequate, but they are still doing something, and I feel they can do more if they really want to. A lot of money is being spent on building infrastructure. I feel that they can cut some expenditure on that and use it here in the time of the flood. I also feel that they can cut 2% of the salary of government employees and use it for relief work. I am a trader and happy to support with what I can, and others can also give proportionally. When so many people are dying, and others are getting displaced, the public should also come forward and support them. Ultimately, society belongs to all of us. It is not just the government’s job to help in times of such great distress.”

While questions are raised on the way the flood situation is being handled, the affected and displaced people look ahead with hope through the veil of uncertainty. We need to look back, introspect and do a reality check on our understanding of the Brahmaputra situation and see if the solutions that we have adopted are reliable enough in the long run and withstand the test of time.

Earth is a complex system that evolved across billions of years, and to understand the forces and processes that act through an intricately interconnected web of cause and effect requires constantly refined scientific methods, more importantly, data from the distant past that holds clues to comprehend the shape of things to come. But are we investing enough in scientific research? The answer may not be an optimal one.

Prof Parag Jyoti Dutta, Member of the Faculty in Geology at Cotton University, Assam, says, “There is no such academic study being funded or financed by the government in our institute. The central government has cut a lot of funds for research. This is not only with regards to the research on floods but also in many other areas. I don’t know what the government is doing. Even my project on landslides is hung. Two of my projects are pending in DST. There is no reply from them. Funds are just not being released by the government. That is the bottom line”.

Man-made causes and current research findings on the Brahmaputra floods

The unimpeded flow the river had from its origins as Tibetan glacial flow is seriously hampered by the ongoing dam constructions. These dams set in critical locations are changing the natural course and the very nature of the river. The effects of such obstructions are felt much later, as it enters Arunachal Pradesh and Assam. In addition to this, an increase in population density has led to more demand for food, resources, and fuel. This has invariably led to increased deforestation resulting in soil erosion. Eroded soil finds its way to the river, filling the river channels with soil that reduces Brahmaputra River’s containing capacity, resulting in over flooding.

In the 2016 doctoral thesis based on research to understand how two interacting stressors – climate change and hydropower development are transforming the riparian landscapes of Northeast India, Costanza Rampini (University of California, Santa Cruz) writes: “As climate change is altering the flows of the Brahmaputra, a multitude of new dams are under construction along its stretches to meet India’s growing energy demands. The impacts of large-scale hydropower development on the Brahmaputra river basin will influence the vulnerability and adaptive capacity of downstream communities to climate change impacts on water resources.”

While weather forecasting remains one of the most unpredictable areas in modern science, with the advancement of technology, refinement of techniques and analytical methods, we have been able to forecast with much better accuracy than before. The study of patterns in weather change and forecasting depends a lot on data, and when we deal with natural phenomena, especially floods, data gathered from the last few decades won’t suffice. As a general rule in data analytics, the larger the data set, the better the possibility of more concrete findings.

Over the last few decades, the study of natural phenomena explicitly pertaining to their implications on earth has evolved into a discipline called the Earth System Model. Here the “Earth system” represents various physical, chemical, and biological forces that interact. Earth System Model (ESM) aims to simulate all pertinent aspects of the Earth system through mathematical and computational modelling based on intricate data analysis.

publive-image A graphical representation of various forces and processes at play in the Earth System Model | Photo courtesy: https://www.climateurope.eu

This helps scientists and other agencies probe into the changing patterns of flood hazards and their risks by simulating various parameters. The best outcome of such modelling and simulation is an anticipatory vigil leading to better preparedness. But the accuracy of such models depends on their validation by historical records and other environmental corroborations, which is minimal or even lacking in some parts of the world. “For example, records of streamflow, an important indicator of flood hazard, go back less than 70 years in Bangladesh and north-eastern India,” says Dr Mukund Palat Rao of Columbia University who along with colleagues, recently did a study that brought together observations from tree ring patterns with climate model projections to build a 700-year history of water discharge from the Brahmaputra river.

For decades many studies have been carried out nationally and internationally on floods. It is unclear to what extent the authorities seriously considered the findings from these studies to mitigate the flood situation. While much of the research points to key insights and common concerns, one can’t help asking if there is a new way of looking at the clues nature gives us that are beyond the obvious.

Most of the studies conducted in the past related to the Brahmaputra river depend on human recorded data derived from discharge-gauge records dating back to the 1950s. But a recent study by a team of researchers from the US and Australia looked at data recorded by nature across centuries. This study looked at water flow across seven centuries in the Brahmaputra River, which suggested that scientists are underestimating the possibilities and potential in the river for massive flooding as temperature increases. What these scientists examined are tree rings which revealed rainfall patterns stretching back to many centuries - the data nature preserved before any historical or human records. These tree ring samples could be extracted by taking a small 5 mm core from a tree using a borer without harming the tree.

publive-image The tree ring extractor process using a borer | Photo courtesy: Dr Mukund Palat Rao

The findings of this study were published in Nature. The lead author of the paper Dr Mukund Palat Rao, says, “In the study that we did in the Brahmaputra river basin, we were able to use network of tree rings sites across the eastern Himalayas to understand how climate in the region has been changing and we combined that with climate model simulation to comprehend what we can expect will happen in the region with climate change to bring together this holistic picture of regional climate and how it has changed in the past and how it will change in the future with time. Through our learnings, we expect - and we are already seeing it right now through floods - that we are going to have more years with extreme rainfall and we are also expecting wetter conditions than what we have seen historically in the past few decades”.

The rings that we see across the cross-section of a tree have a lot more than meets the eye. It is worth considering if the conventional forecasting methods alone are enough to set the ground for better preparedness because a larger data set spread across centuries that the tree ring method relies on is expected to give a much better predictive value compared to conventional methods that rely on a few decades of human recorded data.

Commenting on the variance levels between the conventional methods of analysing human recorded data across last seven decades and the tree rings data across seven centuries, Mukund says: “In terms of the variance, the trees can, of course, only tell us about the past over their lifetimes. Studying tree rings allows us to estimate climate from a few centuries ago. But importantly, they can tell us how the present is relative to the past to help us contextualise where we are currently standing. This is important because our ‘observational records’ of climate and river flow are relatively short (few decades).”

While the results of this study were well received by the Bangladesh Meteorological Department, it does not quite seem to have caught the attention it deserved in India. This is despite the fact that some of the top Indian research institutes like the Indian Institute of Tropical Meteorology (IITM-Pune), IISc Bangalore, Birbal Sahni Institute of Palaeosciences (Lucknow), among others, are working in the same area.

A lot of work, as Mukund says, “is happening around the world, mostly in the US, Europe, and China. But increasingly, this research is expanding. Another big factor is that studying tropical trees is much harder and deforestation of old-growth forests is a big challenge to find old trees. In my research, I am using tree-rings to understand how the forest carbon cycle is changing (the ability of trees to keep growing and accumulate carbon) and to trace timber transport during the 19th century. But I’ve also been involved in investigating how temperatures have been warming in Central Asia.”

It is time for the government and related agencies to do a reality check and ponder if their plan related to flood mitigation is a short-term one or a long-term well thought out strategy based on science and research. If we stick to practices and methodologies that demand restructuring and revision, we are putting people at risk. What is needed is a concerted, coordinated and synergetic interaction between the scientific community, government agencies and the general public. “I guess the main thing we need to do is to better prepare for more intense floods. Investing in more forecasting capability can help, but only if we disseminate these forecasts to the public at the right time,” Mukund remarks.