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Mise à jour hebdomadaire de SciDev.Net: 23 - 30 juillet 2007

La cartographie met en exergue les risques de sécheresse et d’inondation en Afrique

http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=3783&language=1

D’après certains scientifiques, les cartes de l’humidité du sol d’Afrique australe permettront de prévoir les périodes d’inondation et de sécheresse. [Texte complet en Anglais]

African mapping highlights risk of drought and flood

Nell Barrie
27 July 2007
Source: SciDev.Net

The European Space Agency (ESA) has produced maps of soil moisture levels in southern Africa, and says they will help predict floods and droughts. The maps of countries in the Southern African Development Community were published online last week (16 July) and will be available to governmental and independent organisations free of charge. Conventional methods of measuring soil moisture are expensive and inaccurate as each measurement has to be done on-site. ESA’s ENVISAT satellite measures soil moisture levels by emitting radar waves and measuring the energy bounced back by the soil. High levels of soil moisture can lead to flooding and erosion, and low levels cause crops to wilt and die.

Annett Bartsch, project coordinator at Vienna University of Technology, Austria, explained how the maps are used. “Areas of saturated upper soil can be identified with ENVISAT,” she said. These areas are those at risk of flooding.

The maps can also help predict droughts by looking at past trends in soil moisture. “Provided that a long enough reference database is available, anomalies can be identified and thus… drought risk areas identified,” she told SciDev.Net.

In a changing climate, predicting when and where floods are likely to happen is becoming more and more important, according to Geoff Pegram, co-researcher on the project at the University of KwaZulu-Natal in South Africa. “Although we cannot prevent floods, we can anticipate them and hopefully get people out of the way.”

“I think it is really a breakthrough,” said Wolfgang Wagner, professor of remote sensing at the Vienna University of Technology in Austria. He said that the satellite is the first to provide enough measurements over the right timescale to give detailed maps of soil moisture.

The maps have been produced as part of the SHARE project (Soil Moisture for Hydrometeorological Applications in the Southern African Development Community).

The SHARE project is part of ESA’s TIGER initiative, which aims to assist African countries in managing water-related problems by using satellite data. The next stage of the initiative involves transferring leadership of the projects to African authorities.

Related SciDev.Net articles:
Africa’s weather stations need ‘major effort’

Related links:
University of KwaZulu-Natal