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Daily streamflow records for the Lily and Maybell stations were retrieved from the USGS WATSTOR database, and a program (Addailyq) written to add the daily flow values together, creating a synthetic record at Deerlodge Park for water years 1941 - 1986. This streamflow record was deemed as the 'historic' record at Deerlodge Park for the Yampa River. The 1941-1986 water year period was utilized instead of the entire record because previous years had periods of missing data, or estimated flows for entire months. Elliott (1984) examined 10-year increments of flow data at the Lily and Maybell stations and observed that the 1920's had fewer low flow days while the 1930's had greater occurrences of low flows, as compared to the entire period. Streamflows since 1940 were relatively uniform and judged to have had a greater effect upon present channel morphology than flows which occurred earlier in the century. Elliott's report used the 1941-1983 flows, this analysis includes the additional high flow years of 1984-1986. The annual flows for the 1941-1986 water years are shown in Figure 1, along with dashed lines depicting low, average and high water years. Only annual flows were analyzed, variations within individual months and snowmelt runoff periods were not classified, nor deemed necessary for this study. The classification of water years was based upon a log-Pearson Type III distribution, with return periods of 1.25 years, 2 years, and 5 years for the low, average, and high water years, respectively (Table 2). The calculated annual flows are: low water year below 1514 cfs annually average water year 1514 - 2760 cfs annually high water year above 2760 cfs annually An annual flow with a 1.25 year return period has an 80% (1/1.25), in other words, there is an 80% chance equalling or exceededing 1514 cfs in any given year. return period means there is 20% chance of an annual exceeding 2760 cfs in any given year. Thus, there i low or high annual flow occurring in any given year, average year occurring. exceedence probability of of an annual flow Similarly, a 5 year flow equalling or s a 20% chance of either a and an 60% chance of an The same analysis was preformed using-the 1921-1986 period of record (sum of Lily and Maybell stations), with the low, average, and high annual flows determined as 1532 cfs, 2144 cfs, and 2754 cfs, respectively. Only water year 1953 (1517 cfs) changed in classification, from an average to a low water year, as a result of using the entire record available. Thus, as far as classifying wet and dry annual flow years, the 1941-1986 period is adequate.