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Title: DECADE-SCALE PRECIPITATION AND STREAMFLOW VARIATIONS IN THE KANSAS-NEBRASKAREGION

Author
item Garbrecht, Jurgen
item ROSSEL, FREDERIC - USDA, ARS
item Schneider, Jeanne

Submitted to: American Meteorological Society
Publication Type: Proceedings
Publication Acceptance Date: 1/14/2001
Publication Date: 1/14/2001
Citation: N/A

Interpretive Summary: Variations in annual precipitation that last decades or longer are natural occurrences and impact sectors of the economy that depend on weather and water resources, such as agriculture, urban and industrial water supply, drought and flood preparedness, and ecosystem sustainability. In a previous study, above-average precipitation conditions were identified during the last two decades of the 20th century for many regions of the Great Plains. The object of this investigation was to quantify changes in mean annual streamflow of selected river basins in Nebraska and Kansas associated with the observed above-average precipitation conditions. It was found that mean annual streamflow was sensitive to precipitation, with streamflow increasing 2 to 7 times as fast as the associated precipitation increases. These findings point to the vulnerability of surface water supply during extended periods of below average precipitation nin the Nebraska-Kansas region, and to large increases in mean annual streamflow during extended periods of above average precipitation. Further studies are underway to investigate the role of basin size, land use and geographic location on streamflow response to decade-long variations in precipitation.

Technical Abstract: In a previous study, above-average precipitation conditions were identified during the last two decades of the 20th century for many regions of the Great Plains. The object of this investigation was to identify changes in streamflow in Nebraska and Kansas associated with the observed above average precipitation conditions during the 1980-1999 period. The proportionality between the change in mean annual streamflow and mean annual precipitation in the eastern Nebraska-Kansas area was between 2 and 7, with a mean value of about 4. Thus, changes in mean annual streamflow in the eastern Nebraska-Kansas area are sensitive to changes in mean annual precipitation. However, no common multiplicative factor among all river basins could be identified from this data. The increase and the sensitivity of mean annual streamflow were believed to represent conservative estimates because water withdrawals have generally increased over the last two decades of the 20th century and have reduced mean annual streamflow values. Without the water withdrawal the streamflow and the sensitivity to precipitation would have been higher. These findings point to the vulnerability of surface water supply during extended periods of below average precipitation in the Nebraska-Kansas region, and to large increases in runoff during extended periods of above average precipitation. The findings also demonstrated the highly dynamic behavior of the streamflow component of the water budget to decade-long changes in precipitation.