As the International Space Station flew over the Atacama Desert of coastal Peru, an astronaut looked to the north and, by using a short lens (80 mm), captured the entire 190-kilometer (120-mile) length of Lake Titicaca. The lake lies on the high Andes plateau, along the border between Peru and Bolivia. It is the highest major body of navigable water in the world (3,800 meters or 12,500 feet in elevation) and the largest lake in South America. Lake Titicaca is one of the most popular tourist attractions in South America.

Many rivers drain into the lake, including several draining glaciers (top right). A semicircular river delta bulges into the lake (center), while some other rivers enter through protected bays and make dark green wetlands. A green algal bloom appears at the south end of the lake (right). (North is to the top left of the image.)

Strong westerly winds constantly blow across the Andes plateau, ruffling the lake surface in a subtle pattern of waves and swells. These winds contribute significantly to the water budget of the lake. As with most large lakes, there is a balance between inflows and outflows so that the water level remains roughly constant. Hydrologists now know that the Desaguadero River (right) drains only 10 percent of the inflows, with most of the water lost (about 90 percent) because of evaporation caused by the persistent winds.

Geologists have found evidence that the lake stretched hundreds of kilometers farther to the south in the past. Lake Titicaca is believed to have been as much as 600 kilometers (400 miles) long during glacial periods, likely the result of higher rainfall and lower temperatures.

Astronaut photograph ISS040-E-75453 was acquired on July 23, 2014, with a Nikon D3S digital camera using an 80 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by a member of the Expedition 40 crew. The image has 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, Texas State University, Jacobs Contract at NASA-JSC.