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<br />Muddy Creek and Colorado River flow support (see Table 1). This assisted in Reclamation's <br />efforts to limit releases from Ruedi Reservoir to 250 cfs. <br /> <br />Irrigation and Power Diversions <br /> <br />Five irrigation districts serving approximately 70,000 acres ofland in the Grand Valley divert <br />irrigation water from the Colorado River. During periods of peak irrigation demand, up to <br />2,260 cfs is diverted via two diversion dams located upstream of the 15-Mile Reach. A portion <br />of the water diverted (about 582 cfs) is used for hydroelectric power generation and hydraulic <br />pumps to lift irrigation water to the Orchard Mesa. This portion of the water returns to the river <br />at the top of the 15-Mile Reach, unless operation of the Orchard Mesa Check structure is <br />required. The Check is normally operated only during dry years, when river flows are so low <br />that GVrC's senior water rights would result in the upstream diversions for GVWUA and OMrD <br />being curtailed. Using the Check, GVWUA and OMID can "borrow" water destined for GVrC, <br />use it for hydropower and/or hydraulic pumping, and return it to the river upstream of GVrC's <br />diversion dam (see Figure 2). <br /> <br />During 1998, irrigation demand remained normal until mid-September, when some crops had <br />matured and the area received heavy rains. The week of September 16, the GVWUA reduced the <br />Government Highline Canal (GHC) diversion from 1,610 cfs to 1,530 cfs. The following week, <br />they moved 20 cfs to the power canal to generate additional hydropower (this water returned to <br />the river at the 15-Mile Reach). As of September 30, the GHC diversion was at 1,560 cfs, and <br />GVrC had reduced their diversion from 640 cfs to 620 cfs. On October 23, OMID shut off their <br />irrigation system for the season, followed by GVWUA and GVrC the week of November 2. The <br />Orchard Mesa Check was not used during 1998. <br /> <br />IS-Mile Reach Flows (also see Table 1 and Figure 3) <br /> <br />The average flow in the 15 Mile Reach during the augmentation period of August 26 through <br />October 31 was 1,403 cfs. The average flow in the reach during the last six days of August (first <br />six days of augmentation) was 1,262 cfs, and the mean monthly flows for September and <br />October were 1,279 cfs and 1,551 cfs respectively, all above the mean monthly target flow of <br />1,240 cfs. Daily average flows in the 15 Mile Reach, however, dropped below the 1,240 cfs <br />target on 15 days during the augmentation period. Without the reservoir releases, the average <br />for this period would have dropped to 971 cfs, and flows below 1,240 cfs would probably have <br />occurred on 56 out of 67 days. Figure 3 shows the flows in the 15 Mile Reach during the <br />augmentation period with and without releases from the participating reservoirs. <br /> <br />1998 Late SummerlFall Operations <br /> <br />HUP Managing Entities & Water Managers <br /> <br />- 3 - <br />