Considerable attention was paid by the Indian media to the grim finding of the latest Living Planet report that global wildlife populations had dropped by 69% over the past half-century. However, what did not catch its eye was another equally worrying part of the report that found that the numbers of freshwater migratory fish had declined by as much as 76% during the same period. This cannot be treated as an isolated case, as the report points out that though migratory fish are disproportionately more threatened, overall, one in three of all freshwater species are threatened with extinction, including some varieties of river dolphins and turtles.
This is clearly an indicator of the poor health of river ecosystems that in turn poses a threat to the availability of freshwater for humans, particularly in Asia, which is home to just about half the world’s population. Though rivers account for a very small portion of the world’s freshwater source, a very large number of people are dependent on them for their drinking water and food needs. Ten Asian rivers that originate in the Himalaya, for example, flow downstream to the vast plains of the continent, and their deltas, serving the livelihood needs of cumulatively two billion people. Three of these rivers flow through the Indian subcontinent.
Given the dominance of sea fish as a source of food, freshwater fish have rarely received the publicity reserved for whales, sharks and dolphins, with a few exceptions. Among the exceptions, only two iconic Asian fishes have been mentioned in the Living Planet Index (LPI) report—the Mekong Giant Catfish of Indo-China and the Golden Mahseer of India. Both species are known as potamodromous or fish that migrate only in freshwater. The Living Planet report has collected the bulk of the data in this category from Europe and North America. Data about most freshwater species in Asia remains scant.
According to data collected by the LPI, potamodromous fish have shown a decline of 83% between 1970 and 2016—way higher than the overall decline in freshwater migratory fish (73%), many of whom complete their life cycles partly in freshwater and partly in the sea, and the overall decline in wildlife species. The LPI report has blamed dams and reservoirs for the loss of connectivity in rivers, impeding the movement of migratory fish, reducing their ability to complete their life cycles.
“Dams and reservoirs and their up-and-downstream propagation of fragmentation and flow regulation are the leading contributors to the loss of river connectivity,” it says. Dams on the Yangtze in China have, for example, reduced the river distribution of Chinese sturgeon by 50% since they can no longer reach their original spawning grounds. Dams like the Gathega Dam in New South Wales (Australia) not only block migration routes of fish, but also block sediment transport and destroy river habitat, said the LPI report.
Emphasizing the importance of free-flowing rivers for river ecosystems, the report said connectivity provided by them allows unobstructed exchange of material, energy and species within a river system, providing a multitude of services including cultural, recreational, biodiversity, fisheries and the delivery of water and organic materials to downstream habitats including floodplains and deltas. “The connectivity provided by free-flowing rivers is critical for the life history of many migratory fish…to access habitats necessary for the completion of their life cycle.”
Fragmentation of rivers due to dams all over the world has been the rule rather than the exception over the past 60 years as countries emerging from centuries of colonial rule embarked on the fast track towards development to generate employment and feed their populations. Employment generation required large amounts of power and growing more food that required irrigation projects. Both purposes could be solved by building dams.
So, they were built in substantial numbers to meet multiple needs such as irrigation, water storage, hydroelectric power, navigation and flood control. According to the LPI report, today there are as many as 57,985 large dams worldwide and countless small ones. The result of this frenetic dam-building activity over the decades has meant that among large rivers (over 1,000 km) only 37% remain free-flowing, according to the report.
According to LPI data, potamodromous fish have shown a decline of 83% between 1970 and 2016—higher than the decline in migratory fish
China and India, the two countries that have made the most rapid economic progress among developing countries over the past half-century, also happen to be the world’s most prolific dam builders after the United States. It is granted that they set out on this path of development in accordance with the scientific and technological wisdom prevailing during the middle of the 20th century.
It was only after development had run its course for several years that it began to dawn on the country’s planners and policymakers that they may have erred in their choice of development path. Even the first prime minister, Jawaharlal Nehru, who famously characterised large dams as the “temples of modern India”, began to develop doubts later. After witnessing for nearly a decade the ill effects of big dam building, he remarked in a speech to the Central Board of Irrigation and Power in 1958, “We are suffering from what we may call a disease of gigantism.”
Fragmentation of rivers due to dams all over the world has been the rule rather than the exception over the past 60 years
What a free-flowing river does was documented by William Willcocks, a British irrigation engineer famous for designing the Aswan Dam in Egypt, while giving a lecture at Calcutta University in 1930 on the ancient system of irrigation in Bengal. Speaking about the Damodar Valley in Burdwan (Bardhaman), he said, “Floods in the valley began with the monsoon rainfall and with that used to start the sowing and transplanting operations of the paddy. With the advancement of rains, the land used to get damper and extensive surface used to get covered with water, an ideal ground for breeding the mosquito larvae in millions. It is just then that the muddy waters from the river used to gush into the area either by overtopping of the river banks or by affecting the artificial low height embankments along the river with the help of very shallow and wide channels. This muddy water used to contain eggs of carp (rohu), inferior fishes, and finally the shrimps, which would float down through subsidiary channels to the paddy fields, full of rain water and tanks. These eggs would grow into young fishes that were real carnivores and they at once fell upon the larvae of mosquitoes and lived on them. If there was any prolonged dry spell, the local people had dug enormous number of ponds and tanks where the fishes could take refuge and which acted as an insurance against drought. Since the river was made to pass through cuts in the banks at 40 or 50 places, there was little danger of any floods taking place and there was no risk.”
Over the past couple of decades, however, this dominant paradigm of development has been challenged in India itself. Dr Jayanta Bandyopadhyay, an expert in environmental engineering, describes this approach as one of ‘reductionist engineering’. His considered opinion is that “…what is needed is a fundamental shift away from the present reductionist engineering paradigm to a holistic and trans-disciplinary one”. Dr Bandyopadhyay told this writer that 20th century planners generally relied on linear projections of future populations, per capita demand, agricultural production and levels of productivity. “The vision of water resources planners was limited mainly within supply-side solutions.” The ‘changing water paradigm’ represents a real change in the way people think about water and the professional views on water are changing rapidly, he felt.
The concept of reductionist engineering, Dr Bandyopadhyay explained, sees water mainly in the form of visible flowing water. The totality of ecosystem services provided by water, from the time a drop falls on the surface of a river basin to the moment it flows into the sea, have remained marginal and neglected for a long time. As a result, it is not possible for the existing paradigm to recognise and record these various ecological processes and their values, for instance, in the conservation of biodiversity, its role as a mobile solvent, the pushing of the sediment load to the sea and many others.
Urging a change of approach, he suggested the adoption of the ecohydrology approach so that flood waters, usually viewed as catastrophes, are seen in a new light—as a source of free minerals to enrich the soil, free recharge of groundwater, a free medium for the transportation of fish, conservation of biological diversity and free bumper harvests for humans.
Dr Bandyopadhyay’s argument had received support from the late Ramaswamy Y. Iyer, a former senior official of the water resources ministry, who was responsible for drafting India’s first National Water Policy document in 1987. A former Union water resources secretary, Iyer strongly believed “rivers are not human artefacts; they are natural phenomena, integral components of ecological systems, and inextricable parts of the social, economic, and spiritual lives of the communities. They are not pipelines to be cut, turned around, welded, and rejoined….Rivers are far more than mere conduits of water”.
But of late there has been a change in the approach of environmentalists regarding human relationships with rivers. Even in the US, the country that started the old global trend of building large dams, today there is a new trend of taking out or decommissioning dams that either no longer serve a useful purpose or have caused such egregious ecological impacts as to warrant removal. In several instances it has been prompted by a concern for restoration of freshwater migratory fish, recognising their importance for freshwater ecosystems. Two dams have been removed from the Penobscot river in Maine and improvements made to others to result in an increase in the herring population. Since 2012, as many as 1,797 dams have been removed in the United States alone. As many as 69 dams were removed in 23 states of the US during 2020 alone to restore fish, wildlife and river health.
Dams, weirs, and other human-built obstacles in rivers are being removed in several European countries to improve the flow of water
Other economically advanced countries are moving in the same direction. Dams, weirs, and other human-built obstacles in rivers are being removed in several European countries as well, including France, Ukraine, Denmark, Norway, and Britain. Even the Dutch, champion embankment or dyke builders of the world, are now trying to reverse the adverse effects of dykes on fish migration by softening the interface between the sea and inland freshwater. This reflects a gradual recognition among environmentalists and experts that rivers and their ecosystems are part of living systems and must not be treated in a mechanical way.
But this shift is yet to touch Asia, Africa, and South America, where 20th century-style development ideas still predominate. According to figures available, until 2000 as much as 55% of the world’s large dams (more than 15 metres in height) were built in China and India alone. Giant structures have been built or are being contemplated in both countries. China completed the Three Gorges Dam in 2012, while in India the ambitious river linking project is under active execution following a Supreme Court order of 2012 asking the government to implement the project. In neither case were environmental costs considered during decision-making since, in any case, there is a paucity of data regarding the ecosystem of freshwater organisms including fish and a host of others going right up to rhinos and elephants who live in riverine wetlands.