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Information and data was also gathered on twenty-one upstream reservoirs for the purpose of evaluating dam failures and their effects on Grand Junction. A summary tab 1 e was comp 1 eted show ing the owners, contacts, embankment hE! i ght and length, spillway width, storage capacity, peak discha'rge of a potential flood wave at Grand Junction an:! the travel time of the flood wave. HYDROLOGIC ANALYSIS The hydrology used for this study is from a prev'ious study completed in November 1976 by the U.S. Army Corps of En9ineers entit'led "Flood Hazard Information, Colorado River and Tributaries, Grand Junction, ColorCldo". (Reference 3) This is also the same hydrology which was used for the Flood In%lrance Study for Mesa County, Colorado, completed in January 1978 (Reference 1). This information included the 10-, 50-. lCIO-, and 500-year frequency discharges in the Colorado and Gunnison Rivers. For the purpose of this ~;tudy. lesser discharges were required on the Colorado River in order to determine channel capacity throughout the study reach. Therefore, values for the 2-year and 5-year flDOd events were determined by plotting the known discharges on log-probability paper and extrapolating the lesser events. Table 1 shows a Summary of Discharges used in this study. TABLE 1 SUfotIARY OF DISCHARGES (in cubic feet per second) Location *2-Yr. -- *5-Yr. 10-Yr. 50-Yr. 100-Yr. 500-Yr. --- Colorado River downstream of 32,000 Gunnison River 44,000 55,000 73,000 82,000 107,000 Colorado River upstream of 22,000 Gunnison River 32,500 40,000 56,000 63,000 82,000 Gunnison River .~"- at confluence ,~ with Colorado River 1,( ,",,-, ..... I~k." ~ 15,000 17 ,000 20,000 25,000 A frequency curve of these discharges is shown in Figure 5. r 1/i-':'J,'Y', I'--l._ 2