Envirocast® On-Line Feature of the Week -- March 29, 2007

River Plumes Threaten the Great Barrier Reef

The images in this Envirocast® Bulletin were taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA's Terra satellite on February 9, 2007. They show plumes of river sediment washed over a large area of the Greater Barrier Reef east of Australia. This image provides new evidence that even the outer reefs are threatened by land-based pollution including excess sediment, fertilizers, and pesticides.

River Plumes Threaten the Great Barrier Reef

This image from February 9, 2007, shows plumes of sediment flowing into Princess Charlotte Bay, which is about halfway down the east coast of Queensland’s Cape York Peninsula. After heavy rains fell in late January and early February, several rivers were emptying muddy water into the bay.

 

The plumes merge into an 8-mile-wide river of sediment-laden water and veer 47 miles northeast into the Great Barrier Reef. The sediment makes the normally turquoise-colored reef look greenish-brown. The plume veers northeastward away from the first reef, and although the plume becomes fainter, it does reach the outer reef.

Environmental Impacts:

  • In late February 2007, NASA satellite images revealed that even the outer portions of the Australia’s Great Barrier Reef can be bathed in land-based pollution carried far offshore by plumes of river water. Conventional thinking was that river plumes affected only the lagoon and the inner portions of the reef. But images from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite verify a new theory that not even the outer reefs are spared the impact of land-based pollution, which includes excess sediment, fertilizers, and pesticides.

  • According to the scientists at Australia’s Commonwealth Scientific and Industrial Research Organization who first publicized them, the images provide proof that scientists monitoring and trying to safeguard the health of Australia’s Great Barrier Reef must begin to consider the effect of extreme coastal flooding events that can spread pollution much farther than they previously thought.

Reference: CSIRO imagery shows outer Great Barrier Reef at risk from river plumes. Press release from CSIRO. Accessed March 29, 2007.

Supplementary Material:

NASA's TERRA Satellite:

  • The Terra spacecraft (formally known as EOS-AM) was successfully launched on Saturday, December 19, 1999 at the Vandenberg Air Force Base (VAFB) in Lompoc, California. It is flying at an altitude of 705 km (438 miles) observing the Earth. The life expectancy of the Terra mission is 6 years. It will be followed in later years by other EOS spacecraft that take advantage of new developments in remote sensing technologies. [Terra 3D Animation], [Animation showing Terra Orbit]

  • Terra's orbit around the Earth is timed so that it passes from north to south across the equator in the morning, and thus it passes over us at the same local time every day, approximately 10:30-10:45 a.m.

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