Analysis of climatic conditions leading to low streamflows in the headwaters of the Colorado River

Fredrickson, Joshua A. E.
The purpose of my research was to examine the climatic variables associated with recent low streamflows in the headwaters of the Green River in Wyoming. My objectives were: 1) identify years with lower-than-normal streamflows and 2) examine and determine the climatic conditions that led to low streamflows. The climatic variables examined for this study represent surface conditions, atmospheric conditions, and precipitation mechanisms. I examined precipitation rate, temperature, and specific humidity. I also looked at uplift mechanisms—vertical velocity—that enhance or suppress precipitation. The methods I used for my project included: 1) the selection of low-flow years from USGS streamflow data, 2) calculation of composite-anomaly values for low-flow years, 3) creation of composite-anomaly maps of the selected variables for low-flow years, and 4) an analysis and explanation of the composite anomalies. The recent lower-than-normal streamflows in the Green River are the result of varying surface and atmospheric conditions and uplift mechanisms. In general, there was a lack of precipitation during winter months and those dryer-than-normal conditions persisted through spring and into summer/fall. During every season, when there was sufficient moisture available in the atmosphere to allow for precipitation, sinking motions were dominant and suppressed precipitation; and when rising motions were dominant there was not enough moisture in the atmosphere to allow for precipitation, even though the mechanism was present.
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