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<br />. <br /> <br />Reservoir is located on the North Fork Cache la Poudre River just <br /> <br /> <br />upstream from its confluence with the Cache la Poudre River and is used <br /> <br /> <br />for municipal water supply storage. Other reservoirs exist in the moun- <br /> <br /> <br />tains but their contributing areas are too small to be of any conse- <br /> <br /> <br />quence with regard to floodflow alteration. Many reservoirs in the <br /> <br /> <br />plains have small contributing areas and, lacking residual flood <br /> <br /> <br />storage, have little effect on discharges on the Cache la Poudre River. <br /> <br />DISCHARGE PROBABILITY AT GAGE SITES <br /> <br />GENERAL <br /> <br /> <br />A preliminary discharge-probability analysis was made for the <br /> <br /> <br />Cache la Poudre River at the USGS stream gaging stations located below <br /> <br /> <br />Elkhorn Creek and at the mouth of the canyon. The analytical methods <br /> <br /> <br />presented in Bulletin No. 17 published by the Water Resources Council <br /> <br /> <br />(WRC) were used for these gages. The USGS stream gaging station <br /> <br /> <br />located 3 miles upstream from the mouth of the Cache la Poudre River <br /> <br /> <br />near Greeley was analyzed in the 1973 studies using Beard's statistical <br /> <br /> <br />methods. The results of these studies are discussed in the following <br /> <br /> <br />paragraphs. All flood discharges were adjusted for expected probability. <br /> <br />BELOW ELKHORN CREEK <br /> <br /> <br />This gage is approximately 10 miles upstream from Poudre Park. <br /> <br /> <br />The gage is downstream from Elkhorn Creek which, in turn, is about 1 <br /> <br /> <br />mile downstream from the South Fork Cache la Poudre River. Fourteen <br /> <br />years of record from 1946 through 1959 are available for analysis. All <br /> <br /> <br />of the annual peak discharges appear to be from snowmelt. A general- <br /> <br /> <br />ized skew coefficient of +1 obtained from a Corps of Engineers regional <br /> <br /> <br />study of similar streams in Colorado was used to help shape the distri- <br /> <br /> <br />bution. Frequency data for these streams are given in table 1. The <br /> <br /> <br />resulting curve, with confidence limits and adjustments for length of <br /> <br />record, is shown in figure 1. <br /> <br />. <br /> <br />5 <br />