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<br />I <br />I <br />I <br /> <br />Dolores River bclow Rico, the Dolores River at Dolores. and Lost Canyon Creek above the mouth <br /> <br />- were separated into annual raintlood and snowmelt cvcnls. Flows v..'ere classified as rain flood or <br /> <br />snowmelt based on dale of the peak and examination of the hydrographs and recorded rainfall. A <br /> <br />discretionary c1assilicalion of streamflow records was used for the mixed population events, from <br /> <br />rain on the snowpack. When rainfall occurs carly in the season during a period of high snowmelt <br /> <br />runolT, and if the rainfall runolTcomponcnt is small relative 10 the total streamflow, the resulting <br /> <br />runoff peak is classified as a snowmclt-runotTpeak. 'fthe runoff contributed by rainfall is large <br /> <br />relative to the total streaml1o\',:, the peak is classified as a rainfal14nmofTpeak. 'Jl1is analysis is <br /> <br />explained in the U.S. Geological Survey Open-File Report 824426, "Annual Snowmelt and <br /> <br />Rainfall Peak-Flow Data on Selected Foothills Region Streams, South Platte River, Arkansas <br /> <br />River, and Colorado River Hasins. Colorado," dated 1982 (Reference 4-i). <br /> <br />Annual peak llows are available for the three gages in the study area. Reference 44i <br /> <br />tabulated the maximum rainflood and snowmelt peaks for each year of record up to 1977 for the <br /> <br />Rico and Dolores gages. Most of the annual peak events al the two gages arc from snowmelt. <br /> <br />Identification of the annual rainllood peaks after 1977 was not possible for this study. The annual <br /> <br />peak !low record at the Lost Canyon Creek gage includes only one raint:1.II-runoff event peak: the <br /> <br />other annual peaks are from snowmelt. <br /> <br />The rainfall-nmoff events used in the analysis for the two Dolores River gages, in general. <br /> <br />resulted from general rain belween June and October. including general rain on snow in late June <br /> <br />after the highest snowmelt bad already occurred. For Lost Canyon Crcek the sno\\-"ffielt season is <br /> <br />more variable: sometimes rainfall runolToccurs in May. <br /> <br />The general rainstorms of September-October 1911 produced the highest observed peak <br /> <br />!lows at both Rico and Dolores. The llow at Rico is unknO\\ll: the peak flow at Dolores \Vas <br /> <br />30 <br />