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I I I I I I I I I I I I I I I I I I I 002111 Hydrosphere's Colorado River Model December 29, 1993 Page 18 additional points: below Parker Dam and at Imperial Dam. The user will be able to specify mixing parameters or may elect to use those provided with the model. Future versions of the model will compute concentrations at other points in the basin if there is sufficient interest from our customers. Special Operations Special operations have been implemented to simulate the requirements of the operating criteria. In general, these have been developed according to the CRSM code and the System Overview (Schuster, (988) using data from the CRSM control file (USBR, 1991). Important operations are described below. These include administration of a Colorado River Compact call, administration of the Upper Basin Compact, flood control releases, objective minimum release from Lake Powell, inflow forecasting, calculation of the 602(a) storage, equalization of the storage contents of Lakes Powell and Mead, and the declaration and quantification of shortages and surpluses. Compact call The Colorado River Compact of 1922 mandated that the Upper Basin deliver to the Lower Basin a lO-year moving average of 7.5 maf at Lee Ferry. This obligation is implemented in Hydrosphere's Colorado River Model by computing, at the beginning of each month, the average release from Lake Powell over the specified averaging period (10 years in the baseline configuration). If the average release is below the mandated annual mean (7.5 maf in the baseline configuration), then a release required to bring the average up to the Upper Basin delivery target at the end of the month is made from Lake Powell. As implemented in the model, this obligatory release is made even if Lake Powell is empty, in which case some Upper Basin consumptive uses are foregone in order to satisfy the required release. The Compact, as implemented, cannot callout water depletions of the present perfected rights (Le. water rights perfected prior to June 15, 1929, the date of enactment of the Boulder Canyon Project Act) in the Upper Basin. This practice is based on an interpretation of the Colorado River Compact, Boulder Canyon Project Act, the Colorado River Basin Project Act and the U.S. Supreme Court decision in Arizona vs. California. Upper Basin Compact In the event of a Compact call, the Upper Basin Compact takes effect. Previous applications of Hydrosphere's Colorado River Model have not included implementation of the Upper Basin Compact. The commercial version of the model will implement the Upper Basin Compact as follows: in the first month of a Compact call total depletions in each Upper Basin state over the previous averaging period are examined. If any state has exceeded its proportionate share (as defined by the Upper Basin Compact), then curtailment of non-present perfected rights in that state equal to the overdraft will be imposed, up to the delivery deficit amount. If the imposed shortages are insufficient to meet the delivery requirement then curtailment of depletions in the remaining Upper Basin states will be applied on a pro rata basis according to their compact entitlements until the delivery requirement is met. Future versions of the model may include other administrative procedures, depending on feedback from our customers.. Flood control releases No flood control operations are conducted at Lake Powell. Hydrosphere Resource Consultants 1002 Walnut Suite 200 Boulder, Colorado 80302