Dry Rivers Project Summary

Landsat data have since been used in many cases to reveal archaeological sites and interpret their setting. Another spaceborne method that promises to be as useful is radar imaging. Unlike the “passive” sensors on board the Landsat spacecraft, the imagi ng radar is “active.” It provides a source of electromagnetic energy to “illuminate” the terrain. The returned energy is detected by the imaging system and recorded on photographic film. Thus, radar systems can operate independently of lighting conditi ons and weather, because radar rays penetrate clouds.

small radar imageThough the experimenters had no archaeological applications in mind, the imaging radar of the space shuttle Columbia in November 1981 obtained images of a featureless tract of the Western Desert of Egypt. Quite unexpectedl y, the radar waves penetrated the sand cover in this wasteland; the extreme aridity of the area and thus the dryness of the sand grains allowed this penetration. Uncovered were courses of ancient streams, one 20 kilometers across, as wide as today’s Nile Valley.

small radar imageThe revelation inspired field investigations to check the potential of human habitation around these ancient watercourses. Digging through the sand up to five meters in thickness revealed artifacts indication prehistoric human habitation at these sites dating back to approximately 210,000 years ago.

The finding also sparked interest in the potential for groundwater resources in the region. Some of the water of the ancient rivers must have evaporated, and some must have been supplied to the mouths of the rivers, but some must have seeped through the underlying rock to be stored as groundwater. After analyzing the images in 1982, Dr. Farouk El-Baz, who served at the time as Science Advisor to the late President Anwar Sadat of Egypt, suggested to the Egyptian government a program of test drilling. We lls drilled to date prove a groundwater reserve that is capable of supporting agriculture on nearly 81,000 hectares (200,000 acres) for 200 years.

imaging radar
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imaging radar
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