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<br />Ou213,) <br /> <br />Glen Canyon Dam 1998 Annual Plan of Operations <br />prepared in accordance with the Operating Criteria <br />developed for the Grand .Canyon Protection Act (GCPA) <br /> <br />This plan is prepared in conformance with Section 1804(c)(1)(A) of the GCPA. Any changes <br />to the plan would require reconsultation in accordance with this act. <br /> <br />in water year 1997, Glen Canyon Dam was operated in accordance with the criteria <br />established in response to the 1992 Grand Canyon Protection Act, including the constraints <br />on daily fluctuations and ramping rates. Since the annual release volume was 13.8 MAP, <br />powerplant releases were above normal for much of the year. in portions of February, March, <br />June and July average daily releases were 27,000 cfs, and thus were released at a steady flow <br />rate. Lake Powell's peak elevation for the year was 3695 feet and no water bypassed the <br />powerplant. <br /> <br />As a result of the preparation of the Annual Operating Plan under the 1968 Colorado River <br />Basin Project Act, monthly release volumes from Glen Canyon Dam during 1998 are <br />expected to range from 600,000 AP to 1,200,000 AP. Under the most probably inflow <br />. conditions in water year 1998, Glen Canyon Dam is expected to release about 10.75 MAP <br />through the Grand Canyon to Lake Mead. This is about 2.5 MAP greater than the minimum <br />objective release and is the result of high reservoir storage in both Lakes Powell and Mead. <br />Lake Powell is expected to fill in July. Monthly updates to these release projections will be <br />made throughout the year. <br /> <br />With current projected monthly release volumes, hourly powerp1ant releases will exceed <br />20,000 cfs from October through the month of January and again during the summer peak <br />months of July and August, when monthly release volumes are at their highest for the year. <br />Average daily releases of 20,000 cfs are expected during these months. If average daily <br />releases above 25,000 cfs are made, they will be made as steady flows. Projected daily <br />allowable fluctuations therefore will be between 6,000 cfs and 8,000 cfs (see criteria). <br />Minimum releases of 5,000 cfs at night and 8,000 cfs during the day and ramping rates of <br />4,000 cfs/hr increasing and 1,500 cfs/hr decreasing will be followed. All of the above is <br />outlined in the Record of Decision implementing the preferred alternative of the Glen Canyon <br />Dam Environmental Impact Statement. <br /> <br />With the strong current El Nino Southern Oscillation anomaly, there is some indication that <br />winter precipitation could be higher than normal in the southern portion of the Upper <br />Colorado River Basin and that spring precipitation could also be higher than normal in the <br />northern portion of the Basin. Since there are concerns for resulting unplanned spills from <br />Glen Canyon Dam, releases from Glen Canyon Dam are expected to be higher than normal <br />during the fall months in order to achieve a prudent January 1,1998, reservoir storage level. <br />Releases throughout the year will be made in such a way to reduce the risk of uncontrolled <br />spring releases that could result from large forecast errors similar to that which occurred in <br />1983. <br /> <br />11 <br />