Nature & Environment Stories:
Big dams, big problems
Dams have many benefits, but some governments are building them as prestige projects, and these are damaging the environment.
The purpose of dams
Rivers are precious but unpredictable sources of water. They dry up during hot seasons, overflow and cause floods during periods of heavy rainfall.
The construction of dams is one way of controlling a river’s effects. Dams have multiple uses. They can be used to store water, control flooding and generate electricity.
Building a dam in the middle of a river allows water to pool and form a reservoir on one side. The reservoir acts as a ready supply of water during prolonged dry weather. Dams also prevent floods, because, by opening or closing its floodgates, people can restrain the amount of water flowing in the river and prevent it from flooding nearby areas.
In addition, dams produce electricity. The water flowing through a dam’s floodgates can be directed toward turbines, which in turn, spin motors that generate hydroelectricity.
Mega dams lead to unforeseen spending. According to an Oxford University report, governments usually end up paying out double the amount of money they initially set aside for the project. To meet this unforeseen cost, authorities tend to reduce spending on priority projects, such as the building of public health facilities and infrastructure such as roads and power supply lines.
Second, developing countries like Brazil and Ethiopia, embarking on dam-building projects, have had to borrow large sums of money from wealthier nations to do so. But since dam construction takes almost a decade to complete, these nations will take a long time to pay back their debts through returns from their hydroelectric capabilities.
Third, big dams harm the environment. Brazil’s Belo Monte Hydroelectric project — the construction of two dams on the Xingu River in the Amazon rainforest — is one example. In this case, one dam is built to block and divert the Xingu River from its usual path so that in can be forced to pass through man-made canals aimed at flooding 416 square kilometers of the Amazon rainforest, in order to create an artificial reservoir.
As a result, the flora and fauna along the part of the Xingu River, called the Big Bend, from which water is diverted, will not be able to survive, due to lack of water, while the flooding of a section of the Amazon rainforest to build the artificial reservoir will drown plants and animals there.
The Brazilian government says that the shift from electricity produced by the burning of fossil fuels to hydroelectricity generated by the Belo Monte project will reduce the emission of greenhouse gases responsible for global warming. Still, flooding part of the Amazon rainforest means that as vegetation decomposes under the reservoir, methane (a greenhouse gas with more than 80 times the warming power of carbon dioxide) will be released into the atmosphere.
More importantly, about 20,000 to 40,000 people living in the areas affected by the dam construction — including individuals whose homes will be flooded by the artificial reservoir as well as those who depend on the river for fishing and farming — will become homeless.
Bent Flyvbjerg, one of the authors of the Oxford report, told the Financial Times that the social and environmental impacts of mega dams are “often horrendous”. “Taken together, that means it does not make much sense to build them,” Professor Flyvbjerg said.
Another of the report’s authors, Atif Ansar, told FT that leaders of developing countries should put aside their plans to build mega dams if they really care for their people.
An alternative to mega dams
In fact, the authorities can depend on smaller hydroelectric projects that do not require dams. For example, running water can be channeled through a powerhouse containing a turbine and generator to produce hydroelectricity. The used water can then be allowed to flow back into the river. Smaller systems like these are known as run-of-the-river systems and they do not need a dam or reservoir. Producing hydroelectricity this way is harmless to the environment.