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Eyeing Forecast Models' Role for Drier Times

By Luis Pons
July 2, 2004

Have Americans grown used to an overabundance of rain? Scientists at the Agricultural Research Service's Grazinglands Research Laboratory in El Reno, Okla., think so. They want everyone involved in water management today to prepare for normal, drier precipitation patterns.

Soil scientist Jean Steiner warns that drier conditions would increasingly stress water-supply systems, causing water-usage conflicts. She adds that management strategies that account for precipitation variations--and use the latest technologies--should be developed.

One aspect Steiner and her colleagues--hydraulic engineer Jurgen Garbrecht and hydrologists Michael W. Van Liew and John X. Zhang--are focusing on is how computer-generated seasonal forecasts and precipitation-trend data can be tailored to help gauge long-term effects of drier conditions on streamflow and water supplies.

Garbrecht and Schneider studied National Oceanic and Atmospheric Administration records from 1895 to 2001 and found that precipitation over the United States from 1971 to 2000 was about four percent higher than during the entire period studied. It's now been drier over the past couple of years, something the researchers see as perhaps the start of a new trend.

One study, by Van Liew, showed how reliance on abundant rainfall can lead to problems in drier times. When precipitation in an Oklahoma creek was 20 percent greater than average, streamflow increased by 39 percent; but when precipitation was 40 percent greater than average, streamflow increased by 96 percent.

Meanwhile, Zhang related this research directly to agriculture by using seasonal climate forecasts and climate-change projections to measure the effects of short- and long-range variations on water runoff, soil erosion and winter wheat production. He took actual changes in precipitation and temperatures between 1950 and 1999, and those projected for 2056 to 2085, and constructed five climate-change scenarios showing how soil erosion and crop production may change if various climate factors change.

Read more about the research in the July issue of Agricultural Research magazine.

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