Tag Archives: dams and drought

Tying Up the Nile River

Blue Nile Falls. Image from wikipedia
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

Dams and Drought: the Amazon

The city of Itaituba on the banks of the Tapajós River. Image from wikipedia

The São Luiz do Tapajós (SLT) project… would dam one of the last big unobstructed tributaries of the Amazon. The project would provide about a third of the hydropower that Brazil plans for the forthcoming decade, but it would also flood 376 square km (145 square miles) of land where the Munduruku hunt, fish and farm. “The Tapajós valley is our supermarket, our church, our office, our school, our home, our life,” explained Mr Kabá.

The tussle over the Tapajós dam is part of a bigger fight about Brazil’s energy future. SLT is an example of a new sort of hydropower project, which floods a smaller area than traditional dams and therefore ought to cause less disruption and environmental damage. The massive Itaipu dam on the border with Paraguay inundated an area nearly four times as large. But critics of hydropower say “run of river” projects like SLT, which use a river’s natural flow to turn turbines, do not work as well as advertised. Though less destructive than conventional dams, which require bigger reservoirs, they still provoke opposition from people like the Munduruku. Other energy sources, such as gas and wind, are becoming more competitive. Brazil has “an opportunity” to rethink its energy policies, says Paulo Pedrosa, an energy official.

Hydropower has long been Brazil’s main way of generating electricity. Most forecasts suggest it will remain so. The government intends to build more than 30 dams in the Amazon over the next three decades. 

Climate change may worsen the problem. Some climate models predict that river flows in large parts of the Amazon will fall by 30% in coming decades. Deforestation is delaying the onset of the rainy season in some areas by six days a decade, according to research published in Global Change Biology, a journal.   Drought can be expensive. In 2014 power from conventional dams dipped because of a dry spell, forcing electricity companies to buy from gas- and coal-powered generators at high spot prices. The risk of such fluctuations rises with run-of-river dams. Carlos Nobre, a former chief of research at the ministry of science, technology and innovation, thinks more frequent droughts will make future hydropower projects in the Amazon unprofitable.

Brazil’s potential for solar and wind energy is among the highest in the world. The government has promoted them with lavish tax breaks. In the blustery north-east, wind power overtook hydropower this year; wind turbines now generate 36% of the region’s electricity, up from 22% in 2015. The Energy Research Company, a firm linked to the energy ministry, expects renewable generating capacity apart from hydropower to double by 2024.

Generators fuelled by natural gas have been hurt by the subsidies lavished on renewable energy. But, though less climate-friendly than hydropower, they are beginning to compete with it as a source of steady baseload electricity. Brazil now produces gas in abundance as a by-product of pumping oil from its offshore wells. Its marginal cost of production is nearly zero. The future of baseload energy is “hydro-thermal”, rather than hydro alone, says Adriano Pires of the Brazilian Infrastructure Centre, a think-tank in Rio de Janeiro.

Excerpts from Dams in the Amazon: Not in my valley, Economist,  Nov. 5, 2016