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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I. . . I. '. . . . . . . Table 3 shows the USGS gaging stations that contain an adequate record length for computation of peak discharges, Using the gage records, USGS Bulletin l7B procedures were used to calculate discharges for specific return intervals at the gage and are shown in Table 3. a e . ompute ea ISC arees at aelD tatlons Computed Station Total 100-yr Peak 10 Station Name Period-of-Record Years Olscharae (ets\ 09147500 Uncompahgre River At Colona, 1903-1905,1921-1999 82 4,230 Co. 09177000 San Miguel River At Uravan, Co. 1954-1962,1970,1974-1994,1997- 34 14,100 1999 09175500 San Miguel River At Naturita, Co. 1918.1929,1941-1981 53 13,100 09128000 Gunnison River Below Gunnison 1906-1999 94 23,600 Tunnel, Co. 09169500 Dolores River At Bedrock, Co. 1918-1922,1971-1988,1990-1999 33 13,300 T bl 3 C d P k D' h USGS G . S Peak discharges for the Dolores River and the Gunnison River were not estimated using the CWCB regression equations due to their large drainage basin area and influences by reservoirs. The San Miguel River at Naturita gage most closely corresponds to the estimated discharge of the San Miguel river immediately upstream of Dry Creek. The gage analysis shows a peak 100- year discharge of 13,100 cfs at this location, while the CWCB method calculated a peak loo-year discharge of 13,800 cfs. The Uravan gage most closely corresponds to the San Miguel River at its mouth, which had a drainage area too large to use the CWCB equation. Due to the short period of gage records, it is advised that the CWCB estimates be used on the San Miguel where they can be calculated. The Uncompahgre was estimated using both procedures at the Colona gage, The CWCB method estimated a peak l00-year discharge of 6,200 cfs, while the gage analysis estimated 4,230 cfs. Due to the relatively long period-of-record, and the approximate nature of the CWCB methodology, it is recommended that 4,230 cfs be utilized for planning at the Colona gage. The discharges at Beaton Creek and the downstream limits of the approximate study are nearly identical discharges to the Colona gage. Therefore, the same discharge can be used for these locations. As previously discussed, because McPhee Reservoir does not provide flood control storage and because the spillway capacity of 33,000 cfs is greater than the estimated loo-year inflow of 12,000 cfs, it has been assumed that McPhee Reservoir does not affect loo-year flood flows on the Dolores River. In actuality, there will be some flood flow attenuation due to surcharge capacity in the reservoir and travel times from the reservoir inflow points to the spillway, As previously discussed, Ridgway Reservoir on the Uncompahgre River was completed in 1987. A joint use pool used for both flood control and conservation storage, is located in the upper 30 feet of the reservoir. Therefore, the reservoir has capacity to store flood flows and peak discharges downstream of the reservoir will be significantly affected by operation of the 7 -