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Title: DECADE-SCALE PRECIPITATION VARIATIONS, STREAM FLOW RESPONSE AND EXTREME EVENTS IN OKLAHOMA WATERSHEDS.

Author
item Garbrecht, Jurgen
item BROWN, GLEN - OSU
item Van Liew, Michael

Submitted to: Environmental and Water Resources Institute World Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/19/2002
Publication Date: 5/19/2002
Citation: N/A

Interpretive Summary: In the Great Plains, large regions have experienced above average precipitation over the last two decades of the 20th century. This study investigated related changes in annual, seasonal and daily amount of precipitation and streamflow for three watersheds in southern Oklahoma. The purpose of this study was to recognize the size and seasonality of changes in precipitation and streamflow characteristics associated with decade-scale precipitation variations, and to identify differences in streamflow response for watersheds located in different precipitation zones. This information will help identify opportunities for agriculture and downstream water users due to increased precipitation. It was found that the decade-scale precipitation increase and streamflow response were highly correlated and had a highly seasonal character, with a large portion of the additional annual precipitation and runoff occurring during the fall and winter seasons. These are also the seasons with reduced water needs, and the increase in precipitation contributed little to directly alleviate any water supply shortages during the hot season. Changes in number of rainy days, amount of daily and extreme precipitation and runoff events varied by precipitation zone under consideration, with the highest relative variations occurring in the drier, southwestern part of Oklahoma. The high sensitivity of the streamflow response to decade-scale precipitation variations accentuated the importance of considering decade-scale precipitation and streamflow variations in the long term planning and management of water resources.

Technical Abstract: A decade-scale increase in average annual precipitation was observed in the Great Plains during the last two decades of the 20th century. This study investigated related changes in precipitation and streamflow characteristics at annual, seasonal and daily time scales. The purpose of this study was to recognize the size and seasonality of changes in precipitation and streamflow characteristics associated with decade-scale precipitation variations, and to identify differences in streamflow response for three Oklahoma watersheds located in different precipitation zones. It was found that the decade-scale precipitation increase and streamflow response were highly correlated and had a highly seasonal character, with a large portion of the additional annual precipitation and runoff occurring during the fall and winter seasons. These are also the seasons with reduced water needs, and the increase in precipitation contributed little to directly alleviate any water supply shortages during the hot season. Changes in number of rainy days, amount of daily and extreme precipitation and runoff events varied by precipitation zone under consideration, with the highest relative variations occurring in the drier, southwestern part of Oklahoma. The high sensitivity of the streamflow response to decade-scale precipitation variations accentuated the importance of considering decade-scale precipitation and streamflow variations in the long term planning and management of water resources.