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TABLE 4 HYDROLOGIC ANALYSIS AND HYDRAULIC DETER.'HNATlONS STREAMFLOW MEASURING STATIONS Flood Characteristics Floodflows on the Gunni~on River and Tomichi Creek occur consistently during the snowmelt period (April-June) and are occassion- ally augmented by rain. During this period. the precipitation is gen- erally observed to be low at most weather stations in the basin. The period of cloudbursts sctivities occur during the summer monrhs after the high runoff has receded. These activities are normally localized and, therefore, do not produce high flows in the streams. Runoff Gaging Station Beaver Greek at Hierro Blue Mesa Reservoir near Sapinero Gastle Greek near Baldwin Gebolla Creek near Lake City Ceholla Creek at Powderhorn Cement creek near Crested Butte Cimarron River at Cimarron HydrologiC Analysis The hydrologic analyais estnbliahed the peak discharge-fre- quency relationships for floods of 10-, 50-, 100- and 5OD-year recur- reace intervals for hoth Gunnison Rivcr and Tomichi Creek. Srredmflow data for 51 measuring stations located within the Gunnison basin and in the nearby bssins were used in this analysis. A list of these stations ~lth their respective drainage areas and period of recorded peak flows isahown in Table 4. The source of thiadataiS the official lI.S. Ceo logical Survcy water supply papers. A number of correlations bctween historical streamflow rccords of diffcrent ~a~in~ stations were con- ducted. Those correlations with a high coefficient of correlation were used to extcnd the historical recorded data. The recorded and e~tended data wns utilized in frequency analysis to determine flows for the 10-, 50-.100--. and 500-y.,,,r frequ"ndes at respective locations. All cumu- lative frequency distributions were perfoTIlled utilizing the I.o~ Pearson Cimarron River near Cimarron Cimarron Creek below Squaw Creek Coal Creek near Crested Butte Cochetopa Creek near Parlin curecanti Greek near Sapinero East River at Almont East River ~low Ce~ent Cruck East River near Crested Butte Goose Creek at Wagonwhcel Cap Gunnison River below Blue Xesa Gunnison River near Cimarron Gunnison River near Gunnison "ype III ~~thcd, aa ~uggcsted by thc Cnited St~tcs ~atcr Rcsourccs Gunnison River below Gunnison Tunnel CouncilBulletinllutllber15,"AlJniformTechniqueforDecermininJ;F100d Flow Frequencies". A ~umm.ary of the results of this analysis is shown in TableS. Gunnison River at 10la HensonGreekatL"keCity Dis~harge~ for the SOD-year floods for all streams were deter- mined \ltili~ing boch Coo log-Pear.on Type III Method and the .'ltr:\ight- lIn.. extrapol"ci"" of a ~ellli-1og plot of [lood dlsch"rges computed for frequ"'H:le~ up to 100 years. Reault~ ohtetned fro>> Log-Pearson were Lake Fork at Gateview used for design discharges. " " OrainageAre.. (sq.mi.) Period of Recorded PMkFlow 36.0 3,426.0 17.5 25.5 334.0 27.7 212.0 1940 1965 1945 1948 1938 1940 1940 1962 1955 1943 1942 1940 1951 1913, 1918 1935 !Yo" 1940 1955 1963 1904 1912 1916 1945 1901> 1900 1938 1918 1929, 1932 66.0 232.0 8,5 346.0 31.8 289.0 <:J5.U 89.2 90.0 3.453.0 3,650.0 1,012.0 3,965.0 2.490.0 82.0 134.0 1943 Date 1950 1954 1955 1951 1905; 1967 Date 1952 1946 1948 1972 1916 1921, I)"te 1912 1951 Date 1%8 1905 1914; 1928; 1974 Dnte 1903; 1951 1919. 19.38 - n"te 1917