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<br />001685 <br /> <br />Several constraints in the model can alter the amount of additional <br />release computed as described above. If the additional release would <br />cause the total upper basin storage to drop below the 602(a) storage <br />quant Hy, then the amount of addit i ona 1 release is reduced to prevent <br />this from happening. Likewise, the additional release is reduced if <br />it would cause Lake Mead contents to exceed Lake Mead live capacity <br />below exclusive flood control space. <br /> <br />The total release fro:n Lake Powell is constrained by the maximum <br />release specified in the CRSM control file. For Lake Powell, the <br />maximum release is normally set to powerplant capacity. This will <br />constrain the additional release for equalization to the amount that <br />can go through the Glen Canyon Powerplant. If the additional release <br />is reduced because of the maximum powerplant capacity limitation, a <br />greater amount will be released for equalization in subsequent months <br />since the reservoirs will be further out of balance, unless of course <br />the maxi8um release is reached each subsequent month in the water <br />year. <br /> <br />t <br /> <br />A different than norlnal pattern will develop if iidditional releases <br />are being made for equalization and then the spring runoff is signi- <br />ficantly less than the runoff used to predict the EOWY contents. In <br />this case, in the month when the predicted EOWY contents of Lake <br />Powell drops below the predicted EOWY contents of Lake Mead, the <br />model wi 11 reduce the Inonthly releases from Lake Powell to less than <br />the monthly objective minilnum releases in order to not exceed the <br />annoal objective minimum release. What this means is that in order <br />to meet the annual objective minimum release, if the spring runoff <br />was lower than expected and the releases early in the year were <br />therefore greater than needed, then the releases later in the year <br />will be less than that which would normally be needed to meet the <br />objective minimum. <br /> <br />~ <br /> <br />I- <br /> <br />8.2.3 Predj~~ing EOllY Contents <br /> <br />Section 8.2.? discllsses the provision of equalization of the active <br />contents of Lakes Powell and Mead by the end of the water year. In <br />order to satisfy this provision, it is necessary to predict the <br />upcomi ny EOWY contents of Lakes Powell and Mead and of the Upper <br />Basin reservoirs as a total. These predictions begin in January and <br />are made each month through the end of the water year. Note that <br />since the model is a monthly model, EOWY values are values computed <br />for the month of September. <br /> <br />. <br />, <br />, <br />I <br /> <br />For each month, January through September, the model predicts the <br />EOWY live contents of Lakes Po we 11 and Mead. The model fi rst assumes <br />that the Lake Powell releases for the re!nainder of the water year <br />will follow the objective minimum release schedule. The model then <br />computes the Lake Mead releases for the remainder of the water year <br />based upon downstrealn de,nands i I1C 1 udi ng any schedul ed surpl us <br />re 1 eases. L.lke Powell EOWY contents are then predi cted by ba 1 anci ng <br />the current contents, estimated i nfl ow, assumed rel eases, and esti- <br /> <br />35 <br />