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ARKANSAS RIVER FLOODS The Arkansas River originates in the Rocky Mountains of central Colorado near Leadville. The river flows south and then eastward through the Royal Gorge and emerges onto the high plains at Canon City. The river continues eastward through Pueblo, La Junta, Las Animas, Lamar, and into Kansas. A list of the major tributaries above Las Animas is included in table 1 and a basin map is included in figure 2. The Arkansas River valley east of Canon City is an area of intensive irrigated agriculture. The majority of the river flows are derived from snowmelt in the mountains and are diverted from the river by about 12 major irrigation canals. These canals have sufficient capacity to divert virtually all of the normal river flows above Las Animas. The diversions from the river occur in both summer and winter, resulting in normal flows at Las Animas of less than 15 cfs. Floods on the Arkansas below Canon City are the result of intense early summer rainstorms on the high plains. When these rainstorms are produced by the proper combination of meteorlogical factors, the resulting rainfall amounts can be as much as 12 inches in a 24-hour period. This intensity of rainfall on the sparsely vegetated prairie produces very high-yield flooding with over 2,000 cfs. per square mile on some drainages. These floods boil down the normally dry tributary channels and dump into the Arkansas River valley. In the wide river valley, the peak flows from the tributaries are usually rapidly atten- uated by the dense riparian vegetation along the wide, flat flood plain. Occasionally however, the peaks from several tributaries will coincide on the Arkansas with the result of extensive floods. There are two major dams on the Arkansas in Colorado which provide flood control protection. These are Pueblo Dam, located six miles west of Pueblo, and John Martin Dam, located 14 miles east of Las Animas. Pueblo Dam was built by the Bureau of Recla- mation in 1974 as a part of the Fryingpan-Arkansas Project. The dam has a capacity of 357,000 acre feet and provides multi-purpose 3