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News Release

U.S. Department of the Interior
U.S. Geological Survey

Release: April 18, 2003
Sandra Embrey
253-428-3600, ext. 2644

John Clemens
253-428-3600, ext. 2635

Ag Methods Offer Some Water Quality Improvements

[Note: The report can be viewed on the Web at .]

Effective irrigation methods and other agricultural best management practices have improved some measures of water quality, while other measures are slower to respond, according to results of a study published today by the U.S. Geological Survey (USGS).

The USGS study in the Yakima River Basin from 1997 to 2001 found that methods designed to reduce soil erosion and limit surface-water runoff from fields also reduce the amount of soil going into streams and drains. Concentrations of total phosphorus are also reduced by the same methods.

But unlike sediment and total phosphorus, the study found, concentrations of total nitrogen showed little decrease as a result of best management practices. Best management practices are agricultural methods and measures that reduce the flow of compounds into streams, such as using drip or sprinkler irrigation and holding irrigation runoff in ponds to settle out sediment from the water.

"Decreasing concentrations of sediment and total phosphorus correspond with wider use of best management practices," said Jim Ebbert, lead author of the report. "Total nitrogen concentrations in water didn't respond the same way because nitrogen compounds like nitrate enter streams and drains from the ground water, which is affected less by surface irrigation methods.

"But during irrigation season, concentrations of nitrogen and phosphorus do go down as water from upstream reservoirs dilute the concentrations downstream."

The report, "Concentrations and Loads of Suspended Sediment and Nutrients in Surface Water of the Yakima River Basin, Washington, 1999-2000--With an Analysis of Trends in Concentrations," by James C. Ebbert, Sandra S. Embrey, and Janet A. Kelley, is published as U.S. Geological Survey Water-Resources Investigations Report 03-4026. The report can be viewed on the Web at Copies can be purchased from the U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225-0286, telephone 303-202-4200.

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