Earthshots: Satellite Images of Environmental Change

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» Lake Turkana, Kenya and Ethiopia

Lake Turkana, formerly Lake Rudolf, lies in the Rift Valley of East Africa. It is about 250 km long and 15–30 km wide, with an average depth of about 30 m. Lake Turkana is one of the largest desert lakes in the world, and it lies in a closed basin in northwestern Kenya and southwestern Ethiopia. These images show the delta of the Omo River, which provides more than 80% of the water to the lake. The lake has no outlet and lies in an arid area.

Ethiopia is constructing a series of dams on the Omo River. The Gibe I and Gibe II dams are completed, and the Gibe III dam began filling its reservoir in 2015. Studies are ongoing to understand the interactions between regulated flows as a result of the dams and rainfall on the water levels of Lake Turkana. Scientists use many years’ worth of data to get a better understanding of the lake’s natural variability and how that variability might be affected by dams, irrigation, and rainfall.

Map of the featured area.

In these images, bright green indicates aquatic vegetation on the Omo River delta. The size of the delta changes over time in these scenes because of changes to the lake’s water level. The delta expands and shrinks in response to the high rainfall variability in the region. However, if a significant amount of water is diverted from the Omo River for irrigation, the natural dynamics of the lake levels could be affected.

In the 2011 and 2015 images, curious features appear: green swirling shapes south of the delta. We know that green indicates growing vegetation in these images, but is this shallow water being exposed with more aquatic vegetation taking hold, or is this vegetation floating on the water’s surface? Examining the lake’s depth reveals that it is too deep in this area to be growing, rooted plants. So it must be vegetation or weeds floating on the surface.


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