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<br />001G8'; <br /> <br />desired to model the operation of the Colorado River reservoirs using <br />a different objective minimum release from Lake Powell, only the DIST <br />card in the CRSM control file needs to be changed to new monthly <br />values reflecting the changed annual volume. This is the only change <br />required to model with a different objective minimum release from <br />Lake Powell. <br /> <br />8.2.2 Reservoir Equalizing <br /> <br />Articles 11(3) and 11(4) of the Criteria for Coordinated Long-Range <br />Operat i on of Colorado Ri ver Reservoi rs specify that "If, in the pl an <br />of operation, the Upper Basin Storage Reservoirs active storage fore- <br />cast for September 30 of the current water year is greater than the <br />quanti ty of 602(a) storage deterlnination for that date, water shall <br />be released annually fro~ Lake Powell at a rate greater than <br />8.23 million acre-feet per year to the extent necessary. . . to <br />maintain, as nearly as practicable, active storage in Lake Mead equal <br />to the active storage in Lake Powell." Furthermore, the annual <br />r,~lease made for equalization purposes ". . . will be made to the <br />extent that it can be passed through Glen Canyon Powerplant when <br />operated at the available capability of the powerplant. Any water <br />thus retained in Lake Powell to avoid bypass of water at the Glen <br />Canyon Powerplant will be released through Glen Canyon Powerplant as <br />soon as practicable to equalize the active storage in Lake Powell and <br />Lake Mead." <br /> <br />.. <br />[I <br />i <br />~ <br />I: <br />li <br /> <br />The CRSM simulates the reservoir equalizing criteria with the <br />following steps. First, the model computes the quantity of 602(a) <br />storage required by the criteria. Details of this computation are <br />described in section 8.2.4. Next, the model predicts the EOWY con- <br />tents of Lake Powell, Lake Mead, and the Upper Basin reservoirs as a <br />total. Details of how the EOWY contents are predicted are described <br />in section 8.2.3. Next, the model makes. two checks to see if the <br />reservoirs should be equalized. If the total upper basin reservoir <br />contents are greater than the 602(a) storage quantity, and if the <br />predicted EOWY contents of Lake Powell are greater than the predicted <br />EOWY contents of Lake Mead, then the active contents of Lake Powell <br />and Lake Mead are to be equalized. <br /> <br />Releases from Lake Powell for equalization are computed by taking <br />half of the difference between the predicted EOWY contents of Lake <br />Powe 11 and Lake Mead and di vi di ng by the number of months remai ni ng <br />through September. Since the predicted contents are based on sche- <br />duled Powell and Mead releases, the releases for equalization are <br />additional releases which are added to the previously scheduled Lake <br />Powell releases. For each month from January through September, the <br />model recomputes the volume of water that needs to be released from <br />Lake Powell by the EOWY, and di vi des by the number of months <br />remaining through September. This procedure spreads the additional <br />releases for equalization out over the water year and closely equal- <br />izes the two reservoirs by September 30. Since the predicted EOWY <br />contents in any given month are only prOjections, the equalization <br />releases will not exactly balance the reservoirs. <br /> <br />~ <br /> <br />I' <br /> <br />,. <br />\ <br /> <br />34 <br />