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, c CABLE CAR Figure 10. Discharge measurement being made by the U.S. Reclamation Service (the former name of the Bureau of Reclamation) on the morning of June 27, 1921, at the Yuma gaging station, near the peak of the June 1921 flood, At the time o!the phot09raph. measured discharge (based on the measured surtace velocity and a coefficient of 0,9) was 182,000 cubIC feet per second. and stage was 31 feet Photo 'Yuma 1094' taken by the U,S, Bureau of Reclamation, Source of this photograph: 1891-1937 Surtace Water Records File. Colorado River at Yuma, laguna Niguel Federal Records Center, Accession No, 57.78.0006. Box 2 of 2. location No, MB053635. The June 18 peak discharge of the 1921 flood at Lees Feny can also be estimated on the basis of the records from npstream gaging stations, Based on an extrapolation of the stage-discharge rating curve above 40,000 ft3/s, the June 16, 1921, peak discharge at the Colorado River near Fruita gaging station (fig, IA) was estimated to be 81,100 ft3/s (Grover and others. 1922), The June 17, 1921, peak discharge at the Green River at Green River gaging station (fig, IA) was computed to be 65,500 ft3/s (Grover and others, 1922), The stage- discharge rating curve for the Green River at this site was well defined by discharge measurements up to 70,000 ft3/s (Grover and others, 1922), so 65,5(x) ft3/s was probably an accurate value. Although no gaging stations were operating on the mainstem of the San Juan River during 1921, gaging stations on two of the major tributaries, the Animas and Florida Rivers, were used to estimate the likely discharge contribution of the San Juan River to the June 18. 1921. peak discharge at Lees Ferry (fig. IA). The tirst decade of overlap between the Animas and Florida River gaging stations with the near Bluff gaging station. the most downstream gaging station on the San Juan River, was 1928-37, DUling May through June in this period. the combined daily mean discharge of the Anim'Ls and the Florida Rivers accounted for about 40 percent of the next day's discharge of the San Juan River at the near Bluff gaging station (fig. II); thus, the daily mean discharge of the San Juan River at the near Bluff gaging station during May 1921 was estimated by multiplying the combined previous day's discharge of the Animas and Florida Rivers by a factor of2.5, On June 16, 1921, the combined daily mean discharge of the Animas and Florida Rivers was about 8,000 ft3/s. Thus, it is likely that the San Juan River contributed about 20,000 ft3/s to the June 18, 192], peak discharge at Lees Feny. 022<39 Colorado River Floods at Lees Ferry 25