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<br />.. <br /> <br />. <br /> <br />. <br /> <br />002233 <br /> <br />I. ISSUE <br /> <br />Develop an acceptable method of estimating tributary <br />flow frequency, rate, and volume. <br /> <br />DISCUSSION <br /> <br />After determining that there was little actual data on <br />lower Colorado River tributaries, the Technical Subcommittee <br />and staff from involved agencies reviewed data from sites <br />with similar storm and runoff characteristics. Techniques <br />and data from recent reports by the Corps of Engineers and <br />the National Weather Service that addressed tributary flood <br />flows in the phoenix and Las vegas areas were considered. <br />Statistical relationships were developed to transfer this <br />data to the Colorado River tributaries. The professional <br />discussions were conducted in an open forum and a consensus <br />approach was developed. <br /> <br />RECOMMENDATION <br /> <br />The Task Force formally adopted the techniques and <br />processes as defined in the appended report entitled <br />Methodology for Determining the Floodway Flows and Boundaries <br />on the Colorado River. It is recommended that this be the <br />basis by which the Bureau of Reclamation estimate tr ibutary <br />flow frequency, rate, and volume for determination of the <br />Floodway boundar ies. <br /> <br />II. ISSUE <br /> <br />Are near term (next 5 years) possibilities of high <br />releases greater because of the current near full reservoir <br />conditions? <br /> <br />DISCUSSION <br /> <br />The largest flows recorded in the lower Colorado River <br />since the closure of Hoover Dam occurred in 1983. High river <br />flows continued because of full reservoirs and high runoff <br />through 1986. The Colorado River Floodway protection Act <br />came about because of these high flows. Long term <br />projections for the Colorado River Basin forecast that <br />continued development will increase water use, and a return <br />to more normal weather patterns will reduce the likelihood of <br />full reservoirs in future years. The Task Force was <br />concerned that the full or near full reservoir conditions <br />might increase the possibility for significantly greater <br />controlled releases in the near future. When combined with <br />the tributary flows, it might create a higher level of a one- <br /> <br />V-2 <br />