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003JOb Peter Evans, Director 2 1999 Operations Summary The 1999 winter snowpack was below average but by late spring had recovered because of late spring storms, and by late May water supplies had increased enough that the Coordinated Reservoir Operations group made reservoir releases to augment the spring peak flows on the Colorado River. Hydrologic conditions continued to improve throughout the summer and fall, and some reservoirs were spilling in September, while others had to increase releases to prevent spills. Ruedi Reservoir: Releases from the fish pools began September 1 continuing for 63 days ending on November 2. Of the total 31,650 acre-feet available from Ruedi,20,401 acre-feet was needed for the endangered fish flow augmentation, leaving 11,249 acre-feet at the end of the season. Wolford Mountain Reservoir: The 6,000 acre-feet of storage space provided for the endangered fish filled and was available in 1999. Releases from the fish pool began on October 11 and continued for 21 days ending on October 31. Of the 6,000 acre-feet available, 4,939 acre-feet was needed for the endangered fish flow augmentation, leaving 1,061 acre-feet at the end of the irrigation season. The average flow in the IS-Mile Reach during the augmentation period of September 1 through November 2, was 1,797 cfs, or 167 cfs above the mean monthly target flow of 1,630 cfs. The average flow in the IS-Mile Reach during September was 1,752 cfs, and the mean monthly flow for October was 1,817 cfs. Daily average flows in the 15- Mile Reach, however, dropped below the 1,630 cfs target on 16 days during the augmentation period. Without the reservoir releases, the average for this period would have dropped to 1, 168cfs (462 cfs below the target), and flows below 1,630 cfs would have occurred 59 out of 63 days. Figure 1. shows the flows in the IS-Mile Reach during the augmentation period with and without releases from the participating reservoirs. Benefits to Endangered Fish Service biologists report that the combination of a high peak (29,900 cfs in the IS-Mile Reach) in 1995, which stayed above 20,000 cfs until mid-July, followed by a moderately high peak in 1996 resulted in a very successful Colorado pikeminnow reproduction year. This same pattern also occurred in the mid-1980's when two moderately high years (1985 and 1986) fell on the heels of 2 flood years (1983 and 1984) resulting in high reproduction and strong recruitment to the adult population (early 1990's). While it will take several years to confirm, it is anticipated that 1999 also will produce a strong year class. There has been a steady increase in adult Colorado pikeminnow in the Colorado River between 1991 and 1998, particularly in the upper reach, from Westwater Canyon to Palisade, including the IS-Mile Reach. This has primarily resulted from