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Peak streamflows of the Animas River at Durango, Colorado




Milhous, Robert T., author
Colorado State University, publisher

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The Animas River is a tributary of the San Juan River located in Southwestern Colorado. The watershed is on the south-facing slopes of the San Juan Mountains. The annual peak streamflows analyzed in this paper are either the maximum annual instantaneous streamflows or the maximum annual daily streamflows. The annual instantaneous streamflows for the period of record (1908-2009) were analyzed using the log-Pearson Type III distribution. The maximum streamflow between 1908 and 2009 occurred in the fall (25,000 cfs on 5 October 1911) and was found to be 50% larger than the calculated one in two hundred year peak streamflow (16,700 cfs). The second highest peak streamflow in the 102-year series was 20,000 cfs and occurred on 29 June 1927. This snow-melt flood exceeded the 1 in 200 year annual peak streamflow by 20%. The daily streamflow data was used to determine the maximum daily steam flow in the snow-melt period (1 November - 15 July) and during the fall (16 July - 31 October). The median snow-melt maximum daily streamflows was 4350 cfs and was significantly larger than the median fall maximum daily streamflow of 1420 cfs. As with the peak streamflows, the largest fall annual maximum daily streamflows exceeded the maximum snow-melt streamflows. The probable cause of the larger fall streamflows is the atmospheric conditions associated with the North American Monsoon. The infrequent fall floods may be more important from a stream ecology and riparian vegetation viewpoint than the more frequent, but smaller, snow-melt floods.


2011 annual AGU hydrology days was held at Colorado State University on March 21 - March 23, 2011.
Includes bibliographical references.

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