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. Avondale. There was no appreciable inflow to the flood on the Arkansas River between Chico Creek and Las AnilMs and peaks reduced to 43,100 c.f.s. at Nepeata, 31,700 c.f.s. at La Junta, and 22,100 c.f.s. at Las Animas. Below Las Animas runoff from the contrihutin~ area of the Purgatoire River produced a flood peak of 62,500 c.r.s. near the mouth. At Ninemile Dam, on the Purgatoire River, the peak was 105,000 c.f.s. Runoff from the area ahove Smith Canyon, a Purgatoire River tributary, resulted in a peak of 84,000 c.f.s. nt the mouth. . I' I . DISCHARGE FREQUENCY RELATIONSHIPS 27. FOUNTAIN CREEK FREQUENCIES. Continuous recorded data for the gaging station on Fountain Creek at Pueblo are available for water year 1941 through 1965. The gage was discontinued in 1965 and continued again in 1971. Data on peaks prior to water year 1941 are available for the floods of 1921 and 1935. Historical accounts men- tion no other floods on Fountain Creel, at Pueblo since 1894. !luring that year damaging floods at Pueblo occurred on both the Arkansas River and Fountain Creek. Data on their magnitude are not avail- able. Since damage begins at 15,000 c.Ls. on the Fountain Creek at Pueblo, it is assumed that no floods greater than 15,000 c.f.s. oc- curred, other than those of 1921 and 1935, during the period 1R94- 1941, or they would have been mentioned. The corollary assumption that all values above 15,000 c.f.s. since 1894 are representative of the 81 year period is considered as valid. This inclusion of his- torical data is discussed in Appendix 6 of Bulletin I' 17, "Guide- lines for Determining Flood Flow Frequency." A historically- weighted log-Pearson Type III frequency curve was computed using the procedures contained in these guidelines. The computed frequency curve is presented on Plate 3. Shown on the frequency curve are ex- pected probability corrections as discussed in Appendix 11 of WRC Bulletin 17. As an additional measure for judging the merits of the analytical frequency computation of these data, confidence limits were computed for the 0.05 and 0.95 levels of confidence by using the procedures described in Appendix 9 of WRC Bulletin 17. . - . - - 28. VOLUME FREQUENCY. A volume frequency curve for Fountain Creek was developed by using rainfall data from NOAA Atlas 2, "Pre- cipitation-Frequency Atlas of the Western United States," Volume III - Colorado. Loss rates for different frequencies were deter- mined by making successive approximations until the rainfall excess, when applied to the unit hydrograph, would reproduce the same fre- quency peak discharge. The volume frequency curve is shown on Plate 4 and represents a duration of one dsy. An attempt was made to develop volume frequency curves using average 1-, 3-, 7-, and 30- day flows from the Fountain Creek stream gage. The results, how- ever, were not representative of the basin, mainly because flood volumes of the major floods of record are not available. . I- 10 .