geolinde

Toshka Lakes - http://www.earthobservatory.nasa.gov/IOTD/view.php?id=78531&eocn=image&eoci=related_image

Egypt’s Toshka Lakes were created in the 1980s and 1990s by the diversion of water from Lake Nasser through a manmade canal into the Sahara Desert. Flooding of the Toshka Depression created four main lakes (lower image) with a maximum surface area of about 1450 square kilometers—around 25.26 billion cubic meters of water. By 2006, the amount of stored water was reduced by 50 percent. In June 2012 (upper image), water filled only the lowest parts of the main western and eastern basins—representing a surface area of 307 square kilometers, or roughly 80 percent smaller than in 2002. Water is almost completely absent from the central basin.

From space, astronauts documented the first lake—the easternmost one—in 1998. The lakes grew progressively as water flowed further west into each depression, with the westernmost basin filling between 2000 and 2001. The two astronaut photographs above, both taken from the International Space Station, indicate that the lakes were largely depleted by mid-2012, whereas water levels were at their highest in 2002. For scale, the lakes extended 110 kilometers from west to east in 2002.

The more recent image shows lines of center-pivot agricultural fields near the east basin (upper image), which is nearest to Lake Nasser. Sunglint on the western lake makes the water surface appear both light and dark, depending on which parts of the surface were ruffled by the wind at the moment the image was taken.

1. Other images of the Toshka Lakes

2. Toshka Lakes, Egypt (2008)
3. Decreasing Water Levels in Egypt’s Toshka Lakes (2006)
4. Toshka Lakes, Southern Egypt (2000)

Astronaut photograph ISS031-E-148455 (top) was acquired on June 21, 2012, with a Nikon D2Xs digital camera using a 14 mm lens. Astronaut photograph ISS005-E-13562 (bottom) was acquired on September 11, 2002, with a DCS760C digital camera using an 80 mm lens. Both images are provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The images were taken by the Expedition 5 and Expedition 31 crews. They have been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by M. Justin Wilkinson, Jacobs/ESCG at NASA-JSC.

Instrument(s): 

ISS - Digital Camera