This photograph of the northern part of the Mekong River delta was taken by astronauts on the International Space Station on October 24, 2006 at 7:30 GMT. The tail-end of the famed "bird delta" appears in the top-right corner while the city of Go Cong is marked by a star-shaped pattern of roads and canals in the top-centre portion of the scene.

Toward the end of the monsoon season, the Mekong River carries huge amounts of sediment toward the South China Sea, while fertile silt is also deposited annually on the lower flood plain in Cambodia and Vietnam. Published records show that several million tons of soil is being carried toward the lower Mekong in a normal year, reaching more than 300 million tons during severe flood years. The estimation of sediment load and flux is challenging, since the measurements are irregular; however, space-based observation, such as this photograph, aid understanding in relation to climate variations or human activities such as land use alteration and dam construction.

This image of the northern Mekong delta, covering an area of 70 km by 45 km, shows a large plume of suspended sediment in light brown colour, as it is being exported to coastal waters and transported further toward the southwest (lower-left) by along-shore ocean currents. Earth observation satellites have tracked the Mekong river plume in its entirety all the way into the middle region of the Gulf of Thailand. Along the edges of the various arms of the delta, the once extensive mangrove forests can be identified by their dark green colour. Many rural settlements can be traced along the roads and canal network in the light image tone. The predominantly rice-growing agricultural areas appear in lush shades of green. Scientific models have suggested that the Mekong will suffer major siltation and salt water infiltration in this region, which will impact farming and may cause significant environmental as well as socio-economic problems. Earth observation satellites contribute to monitor these changes and assist in integrated coastal zone management.

Photo credit: ISS 014E06242, courtesy of NASA

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Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth (http://eol.jsc.nasa.gov).