Tag Archives: dams storage capacity

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

The Luxury of Swimmable Waters

Data published in 2013 suggested that it was not safe for people to submerge themselves in 60% of New Zealand’s waterways. “We used to swim in these rivers,” says Sam Mahon, the artist. “Now they’ve turned to crap… [T]he real villains behind New Zealand’s deteriorating water quality are still at large…intensive dairy farms…

The first concern is bovine urine, which is rich in nitrogen. Nitrogen can cause toxic algae to grow when it leaches into water. Nitrogen fertiliser, used to increase fodder yields so that more cows can be raised on less land, exacerbates the problem….

At many of the sites where the government tests the groundwater it contains too much nitrate to be safe to drink—a particular problem in New Zealand, since water in much of the country has long been considered clean enough that it is used as drinking water with only minimal treatment. In Canterbury, one of the most polluted areas, expectant mothers are told to test tap water to avoid “blue baby syndrome”, a potentially fatal ailment thought to be caused by nitrates. The poisonous blooms have killed dogs.

An even greater concern for human health comes from cow dung, which contains nasty bacteria such as E.coli….And then there is the damage to native flora and fauna. The algal blooms suck the oxygen from rivers. Sediment washed from farmland can also choke the life out of streams. Almost three-quarters of native species of freshwater fish are under threat.

…One recent tally suggested that just 2,000 of the thirstiest dairies suck up as much water as 60m people would—equivalent to the population of London, New York, Tokyo, Los Angeles and Rio de Janeiro combined. …

Dairies are trying to clean up their act. Farmers have fenced off thousands of kilometres of rivers to prevent livestock from wading in. Some have planted trees along waterways to curb erosion; others remove animals from muddy fields during winter. Some parts of the country are using more sophisticated techniques: around Lake Taupo, the country’s biggest lake, farmers can buy and sell nitrogen allowances in a cap-and-trade scheme. A technique called “precision irrigation” may curb both water consumption and the leaching of nitrogen.

Earlier this year the National Party launched a plan to make 90% of rivers “swimmable” by 2040. Yet it ignored several recommendations of a forum of scientists and agrarians established to thrash out water policy….Environmentalists argue that the national dairy herd should be cut to prevent further damage…And pollutants moving through groundwater can take decades to emerge in lakes. The worst may still be to come.

Excerpts from New Zealand’s Water, Economist, Nov. 18, 2017