Bhutan has four major river basins, and no river in the country will be spared by the hydropower projects, including some small tributaries. All the major rivers have one or more hydropower projects built or lined up, with some rivers like the Punatsangchhu having three projects. Although considered the backbone of the economy of the country, these projects, ecologists and conservation experts say, could wipe out entire river ecosystems that are vital for the support of the rich biodiversity the country always boasts about.
The continuous flow of freshwater is vital for the ecological integrity of rivers and ecosystems, says Karma Chophel of the national environment commission. “The building the hydropower projects will disturb the free flow of rivers.” The ecologist says that Bhutan is one place, where very few unregulated pristine rivers are left in the world. “That’s going to change with the 10 megaprojects.”
Karma Chophel says that no comprehensive study has been done of the flora and fauna and aquatic life to say exactly what is going to be lost, but says that the loss will be devastating. “Studies show that many new species of aquatic invertebrates not found anywhere in the world are present in Bhutan’s river systems. An example is the Epiophlebia laidlawi, a living fossil.”
The first and worst impact would be on the aquatic system, according to chief forestry officer of the nature conservation division, Sonam Wangchuk. Rivers are one of the largest repositories of biodiversity and, when the natural flow of river is dammed, it will affect aquatic life, he says. “When a dam is built, it will stop water and sometimes it has to be released. The sudden gush of released water can wash out an entire ecosystem, which is confined to a certain area,” says the chief.
Although most of Bhutan’s projects are run-of-the-river schemes, environmentalists say diverting water out of the river for power, dams remove water needed for healthy in-stream ecosystems. “The river below the Chukha dam is dead,” says a researcher with the agriculture research centre. “It’s always no water or powerful surges, which erode soil and vegetation and wildlife downstream,” he says. The researcher says that construction of a dam can flood riverside land, destroying riparian and terrestrial habitats. “The backwaters that inundate vast expanse of land can wipe out certain species,” he said. Sonam Wangchuk added that, on naked eye observation, lots of plant species are dying and new species are taking over, because of the disturbed natural habitat.
A WWF vulnerability assessment of Wangchuck centennial park in central Bhutan states that dams block all connectivity between the glaciers and foothills. “If all dams go through as planned, almost all rivers will lose their free-flowing processes between the glaciers to the rest of the system. In river systems elsewhere in the Himalayas, connectivity between glaciers and snow-fed rivers and the rest of the system is an important temperature trigger in the seasonal life cycle of aquatic species, such as the golden mahseer.”
It states that, with changes in temperatures and flows, some dams will form major obstacles to aquatic biodiversity blocking refuge to change, upstream in the system. Dams are likely to exacerbate any impacts of climate change on flow regimes and stream temperatures.”
One evident impact is on the native fish population, says ecologist Rebecca Pradhan of the Royal Society for the Protection of Nature. “Construction of a dam can change a fresh water ecosystem to stagnant water ecosystem, which is entirely different,” said Rebecca, who is in the midst of a project to save the critically endangered bird, the white-bellied heron along the Punatsangchu basin. Rebecca said that, because of the disturbance on the natural habitat, more water birds are seen upstream Phochu recently. “Plant and animal species that thrive, for instance, on one-inch deep water will die once they are submerged.”
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The head of watershed management division, Karma Tshering says there is an impending danger. The whole of Bhutan, according to the head is made of diverse range of watersheds with different characteristics. “When the stable natural process of rivers are disturbed, it will alter the hydrological process,” he said.
As of today, there are 15 projects planned or ongoing on about nine rivers. This is environmentally “very scary” according to ecologists. Some projects like the 720MW Mangdechu project, they say, are located on untouched forest and between two protected areas (Jigme Singye Wangchuck and Manas national parks). “Forests will have to be cleared and watersheds will be disturbed or damaged, resulting in erratic flow of water and the natural ecosystem,” said Rebecca Pradhan.
Commitments are already made for the 10,000MW and there is no turning back. Besides, why should losing micro organisms or river ecosystems stop generating millions of ngultrums in revenue to the government coffer? “For the average person, the hundreds of species of microorganism may not be important, but for the natural world, it is,” says Rebecca. According to the researcher, all ecosystems are interlinked and human beings sit at top of the food web. “When the chain is broken, how can we say it won’t affect humans,” she said.
Mitigation
Conservationists and environmentalists say there is a dilemma as Bhutan is so dependent on its water resources for development, while saving its biodiversity is as important. The government should not commit any more after the 10,000 MW to protect whatever is left of the river systems, says Karma Chophel.
Others said the environment impact assessment (EIA) should not remain only on paper. “Today EIA is just a formality, how much is implemented is a big question,” said the researcher. “Hydropower is the engine of growth and can’t be stopped, but there should be a balance, so the damage is minimal.”
At the rate Bhutan is building hydropower projects, we are making a “water bomb” said another. “We need to hurry, slowly.”
By Ugyen Penjore
