Tag Archives: dams and climate change

Choking the Water: Dams, Dams and More Dams

Since Tibet is part of China, Chinese engineers have been making the most of that potential. They have built big dams not only on rivers like the Yellow and the Yangzi, which flow across China to the Pacific, but also on others, like the Brahmaputra and the Mekong, which pass through several more countries on their way to the sea.

China has every right to do so. Countries lucky enough to control the sources of big rivers often make use of the water for hydropower or irrigation before it sloshes away across a border. But If the countries nearest the source of water, like China,  suck up too much of the flow, or even simply stop silt flowing down or fish swimming up by building dams, the consequences in the lower reaches of the river can be grim: parched crops, collapsed fisheries, salty farmland.

Tension and recrimination have been the order of the day for China and its neighbours… In part, this is because a river like the Mekong does not contain enough water to go round. China has already built 11 dams across the main river (never mind its tributaries) and has plans for eight more; the downstream states have built two and are contemplating seven more. Last year, during a drought, the river ran so low that Cambodia had to turn off a big hydropower plant. Even when rainfall is normal, the altered flow and diminished siltation are causing saltwater to intrude into the Mekong delta, which is the breadbasket of Vietnam, and depleting the fish stocks that provide the only protein for millions of poor Cambodians.

China has long resisted any formal commitment to curb its construction of dams or to guarantee downstream countries a minimum allocation of water. It will not even join the Mekong River Commission, a body intended to help riparian countries resolve water-sharing disputes…

China has not signed any agreements about managing the Mekong with the other countries it flows through, so is not obliged to share a particular amount of water with them, nor even provide data on the flow or any warning about the operations of its dams. It does provide the Mekong River Commission with a trickle of information about water levels and planned releases from dams, which helps with flood-control lower down the river

Excerps from Water Torture: Hydropower in Asia, Economist, May 16, 2020; Torrent to Tickle: the Mekong, Economist, May 16, 2020

Dams on Nile River

Since Ethiopia announced its plan to build the Grand Ethiopian Renaissance Dam, it has inspired threats of sabotage from Egypt, which sits downstream and relies on the Nile for electricity, farming and drinking water. Egypt claims that it is entitled to a certain proportion of the Nile’s water based on colonial-era treaties….

By 2050 around a billion people will live in the countries through which the Nile and its tributaries flow. That alone will put enormous stress on the water supply. But according to a study by Mohamed Siam and Elfatih Eltahir of MIT, potential changes to the river’s flow, resulting from climate change, may add to the strain. Messrs Siam and Eltahir conclude that on current trends the annual flow could increase, on average, by up to 15%. That may seem like a good thing, but it could also grow more variable, by 50%. In other words, there would be more (and worse) floods and droughts.

There is, of course, uncertainty in the projections, not least because differing global climate models give different numbers. But the idea that the flow of the Nile is likely to become more variable is lent credibility, the authors argue, by the fact that trends over decades seem to agree with them, and by consideration of the effects of El Niños. 

More storage capacity will be needed to smooth out the Nile’s flow. But unlike Egypt’s large Aswan Dam, which was built with storage in mind, the new Ethiopian one is designed for electricity production. Once water starts gushing through its turbines, it is expected to produce over 6,000 megawatts of power. It is unclear, though, if the structure has the necessary flexibility to meet downstream demands in periods of prolonged drought.

The talks between the three countries, Ethiopia, Sudan and Egypt, seem to be glossing over the potential effects of climate change. “Nowhere in the world are two such large dams on the same river operated without close co-ordination,” says another study from MIT. But so far co-operation is in short supply. The latest round of talks has been postponed. Even the methodology of impact studies is cause for wrangling.

Excerpts from: Climate Change and the Nile: Flood and Famine, Economist, Aug. 5, 2017