Radar probes water riches

Press, 14 September 1987, Page 28

Radar probes water riches

From

THOMAS LAND

in Geneva

Egypt’s ancient river beds, recently identified beneath the eastern Sahara by radar images obtained from space, are already yielding subterranean water to colonise the land. The next generation of commercial radar re-mote-sensing equipment is scheduled to collect valuable information about the oceans. The radar techniques have also proved their usefulness in mapping the Antarctic. Canada, the European Space Agency and Japan are now preparing to join the United States and the Soviet Union in dispatching radarequipment space vehicles. "Their radar sensors will probably collect more data about the oceans in the next six years than have collected during the past century,” said one specialist at a recent conference.

Consider the success story of radar surveillance in the Sahara, where It has emerged as a potent tool for agricultural development

Each of seven experimental wells drilled by the Egyptians in the Selima Sand Sheet — part of the almost entirely uninhabited Arabian Desert near the Sudanese border — has yielded a rich water supply. The drilling was part of a long series of investigations that confirmed the radar mapping of the region by equipment aboard the second flight of the American space shuttle Columbia in November, 1981.

The Columbia flight produced a set of images depicting the Earth beneath its surface. They identified an unknown world of subterranean river beds, some as wide as the Nile and perhaps 40 million years old; they are hidden by sand. The radar even picked out abandoned Stone Age settlements. ' The discovery was greeted with surprise and scepticism, for 'thA region is one of the driest moat forbidding expanses on Earth: ‘ Specialist* from Egypt and the United States, representing the geological surveys of both coun--trhMLvarious universities and the makers of L iCefigbia’s radar JJJpment, eveataaily confirmed

the sky-eye’s findings after exploring the area on foot. Dr Gerry Schaber, a distinguished American geologist, reported in the scientific press at the time that radar probing had penetrated the surface “through at least one metre in the sand sheets and perhaps several metres through active dune fields.” Practical implications of that discovery are now being explored. They are enormous for navigation and shipping as well as agriculture.

Drilling conducted on the basis the region’s map has tapped a subterranean water supply which is believed to be sufficient to sustain irrigated agriculture over 121,500 hectares. The region is rich in alluvium, once-fertile soil that can be made to work again.

An experimental farm is already blooming. Subsequent space surveys have conducted further radar mapping over Egypt.

Radar works best in regions free of cover, such as the Sahara, the oceans and the icebound poles.

Dr David Drewry, of Britain’s Natural Environment Research Council, has been radar in mapping much of the Antarctic. He can differentiate between sedimentary and igneous rocks, a matter of considerable importance to prospectors and geologists.

Canada intends to launch a radar-equipped satellite soon, primarily to monitor ice movements in the Arctic.

Equipment still on the drawing board will study the major ocean currents, measure the height of waves and track the speed and directions of winds, enabling analysts to predict their behaviour with dependable accuracy. Such information will, in turn, help shipping and oil companies, airlines and fishermen to reduce accidents at sea. It will also contribute to man’s understanding of the influence of the oceans over the Earth’s weather systems.