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<br />C'J <br />"l:t' <br />"l:t' <br /> <br />o <br /> <br />o <br /> <br />The limiting section identified between the Craver Creek and West Beaver <br />Diversions appears to be the most serious constriction in the system. The <br />constriction is the result of the combination of sediment deposition on the inside <br />of a bend in the ditch and a low point on the ditch bank. The constraining <br />section is very localized in extent, and elimination of this constriction would <br />probably not require extensive modifications to the ditch geometry at this <br />location. <br /> <br />o A flow of 400 cfs could still be delivered to the chute even with the upstream <br />constrictions by capturing the required increment of flow at the West Beaver <br />diversion. <br /> <br />o A flow of 600 cfs could be delivered to the reservoir under the following <br />circumstances: <br /> <br />400 cfs is delivered to the chute in Gurley Ditch; <br /> <br />100 cfs is delivered below the chute through West Beaver Highline ditch; <br /> <br />100 cfs total is contributed from Goat and Galloway Creeks. <br /> <br />The 600 cfs delivery scenario described above generally fits the physical capabilities of the <br />system surmised from the data gathered and the experience of the Gurley ditch rider. The data <br />and analyses described in this memorandum do not provide sufficient evidence to reject or <br />modify the values of 400 and 600 cfs adopted for the maximum ditch capacities. This is not to <br />say that the data and analyses conclusively prove that these ditch capacities are correct, but <br />they do lend substantial credence to these values. <br /> <br />Sensitivity Analysis of Flow Measurements <br /> <br />All measured values have an associated error. The magnitude of the error can be reduced <br />through use of the proper equipment, good procedures, and exercising care in making the <br />measurement; but it can never be eliminated entirely. The flow and geometric data gathered for <br />the Gurley Intake Ditch have some error associated with their values, but the magnitudes of <br />these errors are unknown. Through sensitivity analyses, estimates of these errors can be made <br />and the potential effect of these errors on the cJ.lculated maximum capacities evaluated. <br /> <br />Starting with the assumption that all geometric data were collected without error, this simplifies <br />the problem by associating all errors with the flow values. Following good procedures, flows <br />can be measured with an accuracy of approximately .:t. 10 percent through current metering. <br />With all geometric data exact, use of flow values accurate to.:t. 10 percent to evaluate "n" and <br />calculate maximum flows would produce estimates within.:t. 10 percent of their true values. At <br />the very best, the calculated maximum capacities are within.:t. 10 percent of their true values. <br /> <br />A more realistic approach is to recognize that all of the measurements have an associated <br />error. An estimate of the error for each type of measurement can then be made and an <br />estimate of the net uncertainty in the calculated result, which has a functional relationship to the <br /> <br />7 <br />