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In normal years, any water in excess of approximately 25,000 acre feet will have to be released. <br />During these releases, or at any other time, flows should not exceed 2,500 cfs at Magote, nor 1,600 <br />cfs at La Sauces. <br />In order to model the COE flood control operations, during each time step from March 1 to May 1 <br />(seven 10-day time steps), the model calculates the allowable May l Of' storage based on the current <br />April to September forecast. If the current storage level is greater than the allowable May l Otn <br />storage, the model calculates the necessary drawdown on a linear basis to achieve the May l Otn <br />target. The reservation curve for Platoro never calls for drawdowns in excess of 10,000 acre-feet. <br />Flood control releases made by the model respect the maximum user-defined river flows at Magote <br />and at La Sauces. <br />When water is being forced out of Platoro to meet flood control criteria, a compact credit for the <br />amount of the release occurs. Platoro is only allowed to refill--which it should normally do if the <br />COE curves are accurate--by its junior storable flow right. It is possible, however, that Platoro will <br />not recover the flood control release, especially if the reservoir carryover is high and the forecasted <br />inflow turns out to be much less than predicted. <br />The third aspect of flood control involves the prevention of high flows at either Magote (2,500 cfs) <br />or Las Sauces (1,600 cfs) because of precipitation events. This feature is currently not explicitly <br />modeled because the model will automatically allocate water to Platoro general pool storage when <br />these high flows occur. <br />Only one instream flow right is represented in the model: Legislation (H.R. 429) transferring <br />ownership and operations responsibilities of Platoro Reservoir from the Bureau of Reclamation to <br />the Conejos District mandated winter (October through April) target flow of 7 cfs below Platoro. <br />This right is met by releases from the general pool If the general pool is empty, the permanent pool <br />is used providing that the reservoir has at least 2,400 acre-feet in total storage. Under no <br />circumstances is the reservoir reduced to less than 2,400 acre-feet to meet winter instream flow <br />releases. H.R 429 also specifies a summer release of 40 cfs or inflow, whichever is less. Because <br />the downstream water rights always calls at least this amount past Platoro, usually it is not necessary <br />to model this release. The model forces a bypass if exceptional circumstances prevent such a <br />release. <br />Modeling Administration of the Rio Grande Compact <br />The CRPM respects Rio Grande Compact deliveries by operating the Conejos River basin in <br />accordance with current operating practices of the State Engineer. In general this means that in <br />every time step, a percentage of inflows to the Conejos basin are ineligible for diversion and are <br />routed past the La Sauces gage so that a compact delivery credit can be achieved. The model user, <br />however, may override the automatic curtailment calculation and force the model to respect any <br />amount of curtailment, including no curtailment, if desired. <br />Modeling compact administration relies heavily on forecasted inflows for the entire year and <br />knowledge of past deliveries. A curtailment percentage are calculated by dividing the remaining <br />required compact deliveries by the remaining inflows. In reality, the Compact calculations <br />performed by the model are more complex than this description would indicate but the overall logic <br />is the same. Additional information concerning actual Compact administration is provided in a <br />memorandum documenting discussions with the Division 3 Engineer. <br />The estimated total annual compact delivery is normally based on exactly reaching the delivery <br />C:\cdss\Task3Mem.doc Review Previous Modeling Efforts Apri16, 1999 -Page 5 of 11 <br />