Earthshots: Satellite Images of Environmental Change

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» Gibe III Dam, Ethiopia
 

The great thing about hydropower is that it’s a renewable nonpolluting source of power. Once it’s up and running, operation costs are relatively low, and the energy supply is very reliable.

In the United States, most of the best locations for hydropower have already been taken (such as Hoover Dam near Las Vegas and the Glen Canyon Dam). Other countries are starting large hydro projects to further development and provide reliable power for more communities. In Ethiopia, for example, a series of large dams on the Omo River provide electricity for the country and enough to export to neighboring countries. They also provide irrigation water for large-scale agriculture.

Hydropower projects of this scale often come with downsides as well.

Large hydropower projects can have a massive effect on the landscape. Reservoirs can change local ecosystems and fish habitat, and sometimes displace large populations of people. In the case of the Gibe III dam, the rapid changes could have substantial effects on the people living downstream who depend on the river’s regular pulse floods for farming and fishing.

Gibe III is the third hydropower plant on the Omo River, what they’re calling a hydroelectric cascade.

The Omo River has a unique geo-political dynamic. The river is entirely contained within Ethiopia’s borders. However, the river empties into Lake Turkana, which lies almost entirely within neighboring Kenya to the south.

Map of the featured area.

At nearly 244 meters tall, Gibe III is Africa’s tallest dam and the continent’s third largest hydroelectric plant. Its estimated production capacity is 6,500 GWh a year.

The first large dam on the Omo River, Gibe III takes its name from a tributary of the Omo, the Gibe River, on which two smaller dams were previously built. The Gibe I hydroelectric turbine was installed in 2004, and Gibe II in 2010. Gibe IV and Gibe V are planned to be built on the Omo downstream of Gibe III.

Construction of Gibe III began in 2006. The reservoir, now 155 kilometers long, began filling in February 2015. The reservoir fills the entire canyon that the river flowed through. The dam began generating electricity later in 2015 and was fully commissioned in December 2016.

The electricity generated by the dam is also exported to Kenya and other countries, bringing in hundreds of millions of dollars of revenue for Ethiopia. Electricity can also be delivered to Ethiopia’s rural areas, where just 26.5% of the population had access to electricity in 2015.

Located 450 kilometers south of the capital Addis Ababa, the dam is also used to regulate floodwater and provide water for irrigation. However, the dam ended the natural annual flooding that brought nutrients to the banks of the Omo River. The lack of floods makes it more difficult to grow food there.

An artificial regulated flow through the dam was intended to mimic this natural flood pulse. But the dam traps sediment, so even with regulated flow through the dam, there will still be impacts on wildlife and farming because of the reduced nutrients from this sediment.

Because the Omo River accounts for 90% of the inflows to Lake Turkana in Kenya, there are major effects on the water levels and water quality of that lake, especially now that the water is used for other purposes such as large-scale irrigation. Furthermore, the reduced flow from the Omo causes increased salinity in Lake Turkana, which can affect some fish species.

About 160 kilometers downstream from the dam are large irrigated sugar plantations. Made possible by the dam, land clearing for these plantations began in 2012.

In the imagery, the plantations are the blocky shapes near the Omo River. According to one source, 100,000 hectares of land are planned for sugar plantation development.

Sugarcane has a high water requirement. These plantations and associated agro-chemicals for this irrigation and the plans to build two more dams on the Omo River have many concerned about the long-term effects on Lake Turkana and the livelihoods of people who rely on the water supply to the lake provided by the Omo River.

Tribal communities in the lower Omo and Lake Turkana region rely on traditional farming, herding, and fishing, activities that depend on the water and nourishing floods from the Omo River.

Landsat helps communities track landscape change and the effects of large hydroelectric and irrigation projects, wherever they are in the world.

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