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<br />-~ <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Bureau of Reclamation. The projects transport CBT and VGP water across the <br />Continental Divide and deliver that water to shareholders along the Front <br />Range and in northeastern Colorado. <br /> <br />I <br />I <br />I <br /> <br />The first step in pursuing the study objectives was to determine the <br />physical supply of water that would be available in any given month in the <br />Big Thompson River and from the CBT and Vindy Gap projects. Since <br />streamflow is highly dependent upon such natural factors as rainfall, <br />snowfall and snowmelt, this determination is based upon probabilities and <br />expected extremes rather than constant values for any given month or period <br />of months. Techniques used to define streamflow characteristics during <br />low-flow periods are referred to as "drought analyses." <br /> <br />I <br />I <br />I <br />I <br />I <br /> <br />Statistical techniques were used to supplement the analysis of historic <br /> <br /> <br />data. These techniques were used to generate long-term (one thousand <br /> <br /> <br />year) records of "synthetic" streamflow for the Big Thompson, CBT and VGP <br /> <br /> <br />watersheds. These synthetic streamflow histories maintain the monthly, <br /> <br /> <br />seasonal, and annual characteristics of the historic records (mean flows, <br /> <br /> <br />standard deviations), but also provide a much greater combination of above <br /> <br /> <br />and below-normal streamflows. The synthetic records thus allowed the water <br /> <br /> <br />supply system to be tested against a wide range of conditions that may not <br /> <br /> <br />have been observed in the historic records but are nevertheless possible in <br /> <br /> <br />the future; this provides a more reliable estimate of system yields than <br /> <br /> <br />could be obtained from evaluation of the historic data alone. Generation <br /> <br /> <br />of a long-term synthetic record provides a more extensive number of drought <br /> <br /> <br />events against which the design drought event can be compared and its <br /> <br /> <br />severity more accurately determined. <br /> <br />I <br /> <br />Vater Demand - Consideration of the magnitude and variability of the demand <br />for water are important when evaluating the reliability of a given system <br /> <br />I <br />I <br /> <br />I <br /> <br />ii <br />