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<br />Dolores River below Rico, the Dolores River at Dolores, and Lost Canyon Creek above the mouth <br /> <br />- were separated into annual rainflood and snowmelt events. Flows were classified as rainflood or <br /> <br />snowmelt based on date ofthe peak and examination ofthe hydro graphs and recorded rainfall. A <br /> <br />discretionary classification of streamflow records was used for the mixed population events, from <br /> <br />rain on the snowpack. When rainfall occurs early in the season during a period of high snowmelt <br /> <br />runoff, and if the rainfall runoff component is small relative to the total streamflow, the resulting <br /> <br />runoff peak is classified as a snowmelt-runoff peak. If the runoff contributed by rainfall is large <br /> <br />relative to the total streamflow, the peak is classified as a rainfall-~offpeak. This analysis is <br /> <br />explained in the U.S. Geological Survey Open-File Report 82-426, "Annual Snowmelt and <br /> <br />Rainfall Peak-Flow Data on Selected Foothills Region Streams, South Platte River, Arkansas <br /> <br />River, and Colorado River Basins, Colorado," dated 1982 (Reference 4-i). <br /> <br />Annual peak flows are available for the three gages in the study area. Reference 4-i <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 at the two gages are from snowmelt. <br /> <br />Identification of the annual rainflood peaks after 1977 was not possible for this study. The annual <br /> <br />peak flow record at the Lost Canyon Creek gage includes only one rainfall-runoff event peak; the <br /> <br />other annual peaks are from snowmelt. <br /> <br />The rainfall-runoff events used in the analysis for the two Dolores River gages, in general, <br /> <br />resulted from general rain between June and October, including general rain on snow in late June <br /> <br />after the highest snowmelt had already occurred. For Lost Canyon Creek the snowmelt season is <br /> <br />more variable; sometimes rainfall runoff occurs in May. <br /> <br />The general rainstorms of September-October 1911 produced the highest observed peak <br /> <br />flows at both Rico and Dolores. The flow at Rico is unknown; the peak flow at Dolores was <br /> <br />30 <br /> <br />e <br /> <br />e <br /> <br />-- <br />