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Predicting Flooding Earlier By Mapping Soil Moisture

By Don Comis
August 24, 2001

Within 10 years, daily newscasts may include weather reports based on soil moisture maps that can predict floods in their infancy, along with droughts, tornadoes and hurricanes.

On a prototype of just such a map, signs of the April 12 Mississippi flood first appeared on March 29 as a small, blue patch of oversaturated soil in the Dakotas. Knowing the terrain and water systems, it would have been easy to predict that the water would end up in Mississippi. Agricultural Research Service hydrologist Tom Jackson prepared the map after the flood, using satellite data.

The actual maps will come from sensors aboard a pair of U.S.-European long-range weather-forecasting satellites proposed for launch in 2008. A similar sensor will also be mounted on NASA's soon-to-be-launched Aqua satellite. Each dish measures soil moisture by capturing the soil's natural microwave emissions.

The sensors are part of a Soil-Moisture Observing System envisioned by Jackson, who is with ARS' Hydrology and Remote Sensing Laboratory in Beltsville, Md. The Henry A. Wallace Beltsville Agricultural Research Center has land adjacent to NASA's Goddard Space Flight Center in Greenbelt, Md.

Together with NASA and other agencies, Jackson and colleagues tested Aqua's sensor in airplane and satellite flyover campaigns in Arizona and Oklahoma and will soon test it in Iowa. From this research, techniques have emerged that will be used to translate Aqua's data into maps.

Jackson is calibrating the sensor with ground data from ARS soil moisture instruments in Arizona, Georgia, Oklahoma and Idaho. He is also using data from 40 USDA Natural Resources Conservation Service ground-monitoring stations across the country. The NRCS data, available on the World Wide Web at, can be read one hour after being collected, 24 hours a day.

For more details, see the August issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.