A Grand New Dam on the Nile

With three spillways and 13 turbines, the concrete structure will rise 145 meters (475 feet) and create a reservoir that will cover 1,874 square kilometers (724 square miles) of land, an area about the size of Houston, Texas. Called the Grand Ethiopian Renaissance Dam (GERD), it should more than double Ethiopia’s output of electricity.

If it works as planned, GERD will usher in a new era and help brighten the mostly dark landscape that appears in nighttime images of Ethiopia. (In the Suomi-NPP satellite composite below, note the contrast between the darkness of Ethiopia and the bright trail of light along the Nile River in Egypt, where World Bank data indicates that 100 percent of the population has access to electricity.) In addition to generating electricity, GERD should temper destructive seasonal floods in Sudan, boost food supplies in Ethiopia by providing reliable irrigation water, and extend the lifespan of other dams downstream on the Nile by trapping sediment.

However, by changing the river’s hydrology, the dam may have an impact on millions of people who live and farm downstream in Egypt and parts of Sudan and use the Nile’s water. The natural-color image of the Nile’s Great Bend shown below underscores how much the people of Egypt depend on the Nile: 95 percent of Egypt’s farmland is found within a narrow zone near the riverbanks.

After 10 years of construction, GERD is almost complete. In 2020, water managers started filling the reservoir, a process that could take from a few years to a decade depending on weather conditions and how much of the Blue Nile’s flow the dam managers hold back. Ethiopia has an incentive to fill the reservoir quickly to start generating power and start paying for the $5 billion dollar project. However, rapid filling could significantly reduce the water downstream since the Blue Nile provides 60 percent of the water that flows into the Nile.

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on NASA's Earth Observatory website