In considering the various solutions to meeting Africa's current and future energy requirements ('Powering Africa'--African Business, January 2010 issue), you comment on the "sizable negative side effects [that] accompany nuclear and large hydro schemes" without spelling out their impacts in detail. And yet, while nuclear seems to be out of the equation for Africa for the present, hydroelectric generation developments are being encouraged in some quarters as a way to boost Africa's economic growth. It is being implied that major hydro schemes are a comparatively benign energy source, but a number of experts disagree.
In general, hydroelectric dams involve construction that requires the production of thousands of tons of concrete--a process responsible for generating carbon emissions. Dams also involve the building of large, expensive grid infrastructure to carry the power they generate to end users, whether residential or industrial consumers.
This has cost implications and other problems--usually dams are located some distance from populated areas.
But, along with this problem, the construction of large dams completely changes the relationship of water and land and that has the potential to damage delicate ecosystems.
Furthermore, dams invariably hold back the sediment load normally found in a river flow. As well as contributing to downstream erosion, this sediment contains organic matter that usually builds up behind a dam wall. It will over time decompose and emit methane--a powerful greenhouse gas.
It is also known that the reservoirs behind dam walls built in tropical regions provide...