By Sayanangshu Modak, research assistant at the Observer Research Foundation, Kolkata
At this time almost every year, South Asia grapples with rainfall and consequent floods over large parts of Eastern India, Nepal and Bangladesh. This year is particularly challenging as a pandemic is also underway. Their unique geography, of fertile plains well-drained by river channels in the middle and lower stretches of the Ganga-Brahmaputra-Meghna (GBM) system, turns into a curse with the onset of the monsoons. Then again, the same periodic movement of moisture-laden winds has contributed to the region’s prosperity for centuries.
What then has changed over the years to transform these life-giving rains into a wrath that needs to be ‘dealt with’?
The GBM Basin is a major transboundary river basin over 1.7 million sq. km of land, distributed among five countries: India (64%), China (18%), Nepal (9%), Bangladesh (7%) and Bhutan (3%). The river systems are located in the monsoon belt, so the rivers’ flow regimes are heavily influenced by the South Asian monsoons. About 84% of the rainfall occurs from June to September, and 80% of the annual river flow takes place in the four months from July to October.
Distribution of annual rainfall is also non-uniform, ranging from less than 500 mm in Tibet and below 1,000 mm in parts of the western and south-western fringes of the Ganga basin to 4000 mm in the northern extent of the Meghna basin. As a result, the basin has had a flood-drought syndrome: the rivers flood during the monsoons but for the rest of the year, parts of the basin are dry, and the people there depend on groundwater.
The Government of India has often used this as a reason to pitch for and build large water storage and diversion projects, in ostensible attempts to even out the availability of water.
Indeed, historically, the institutional response to the uneven rainfall distribution has been to construct large infrastructure to store and divert water available during the monsoons. The floodplains have always favoured settled agriculture because of the level topography and the availability of fine-grained, nutrient-rich and moist overbank deposits. Subsequently, with the advent of the means and tools to control inundation, transport water and practice modern agriculture, the floodplains in this part of the world have become sites of dense human settlements and intensive agriculture.
In 2001, Dinesh Kumar Mishra penned an elaborate account of people living in harmony with floods in the flood-affected regions of India and Bangladesh, using the floodwaters in the best possible way while ensuring the least damage. Flood-tolerance as a design principle was everywhere. However, colonial imperatives required altering the floodplains in the subcontinent at a scale and magnitude like never before.
A 2008 study observed that the colonial dispensation had embarked on building embankments as they served two purposes: to save standing crops, which are not flood-resistant, and second, to expand agriculture to hitherto uncultivated areas. The British cultivated a conviction that continues to this day that embankments were crucial to maximise profits and reduce flooding losses.
As a result, small irrigation works like bandh and pyne were replaced by larger projects involving networks of canals. Together with an explosion in the length of railways and roads, they obstructed the free flow of rivers.
This paradigm of reductionist ‘flood-control’ continued in the postcolonial period. Large-scale water interventions in the form of extensive embankments, high dams and water diversion projects became the dominant institutional response to prevent floods. But the haphazard and unscientific construction of embankments also meant that the silt that would get distributed within adjacent plains during floods now began accumulating in the river channel. As a result, the river bed became raised over time.
The government also commissioned several multipurpose projects to control floods while meeting the demands for energy generation and irrigation water-supply. Simultaneously, from the late 1950s, the inevitability of flooding despite the adoption of the best flood-control strategies started to feature in India’s policy circles.
In 1980, the National Flood Commission signalled a paradigm change in mitigating damage caused by floods with a mix of structural and non-structural measures. Since then, a new phase in flood governance has firmly assumed the centerstage – one that seeks to reduce the risk of floods while building the resilience of communities living in India’s flood-prone areas.
This paradigm change has resulted in a breakaway from the older approach, and the adoption of multi-pronged strategies to govern floods in the GBM basin. However, the losses incurred due to floods and the risks posed by extreme rainfall (table 1 and figure 2) have remained significant challenges. This is primarily because, by the 1980s, the floodplains had undergone large-scale changes, including hosting a greater density of humans.
Although the monsoonal rains are a regional – and not national – phenomenon and the floodwaters are not confined to national boundaries, the approach to flood governance has largely been confined to territorial jurisdictions. While data-sharing agreements do exist between nations to facilitate early warning systems, an institutional arrangement with a long-term vision and the overarching mandate of integrated river basin governanceis missing. Such an institutional arrangement could help manage the rivers’ flows – both when they’re lean and in spate.
For far too long South Asia has had to live with the impression that the rivers’ high flows pose a risk that needs to be ‘contained’ – diverging from the idea of flood-tolerance intrinsic to this region. The subcontinent’s rivers are most active during the summer monsoons, when they carry out a host of geomorphic functions including the erosion, transportation and deposition of sediments. Therefore, large-scale modifications of the floodplains by building dams and embankments and diverting flows could further impede these functions, and overall affecting river-floodplain connectivity.
Experts know today that when floodwaters of the large rivers, including the GBM system, are caught behind dams during peak flood discharge, a large amount of sediment is trapped as well. According to one 2018 study, the sediment load in the combined flow of the Ganga and Brahmaputra is decreasing at a rate of 4-10 million tonnes a year. From a previous estimate of mean annual sediment load of 1-2.4 billion tonnes per year, the sediment load in the GBM system had fallen by 2015 to 500 million tonnes per year.
As of today, this is still sufficient to offset the combined effects of land subsidence and sea-level rise. But unsustainable practices upstream and midstream of the river system could soon push the balance past a point of no return.
All these facts together only reinforce the case for a strong collaboration between South Asia’s riparian nations, especially with climate change in the picture. Regional cooperation with a holistic vision may be the only way to resolve any disputes that may arise in the future, from the novel water, energy, biodiversity and sediments (a.k.a. WEBS) perspective on river governance.