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uO~G99 Steve Schmitzer's Comments February 18,2003 Randy Seaholm Colorado Water Conservation Board 1313 Sherman Street, Room 721 Denver, CO 80203 Dear Randy: Subject: Phase 2 Coordinated Facilities Water Availability Study for the Endangered Fishes of the Upper Colorado River, Draft, January 2003. The following comments are in response to the above-referenced report and the January 17,2003 meeting at Denver Water. General The report should clearly acknowledge that STATEMOD has inconsistencies and limitations. Report will acknowledge limitations, not inconsistencies. As implied on page 41, using STATEMOD with a monthly time step is insufficient to simulate both CROP bypasses/releases and CFOPS bypasses/releases. It is our understanding that the state plans to update STATEMOD to a daily model to more correctly simulate operations. The daily time step problem is especially apparent in attempting to simulate Denver's exchange and substitution operations. Although STATEMOD was modified to more correctly model exchange and substitution operations, problems are still apparent. For example, on page 40 (and Figure 34) the report states that with 110,000 af of future demands (50,000 af of which is increased demand on Dillon Reservoir), Williams Fork Reservoir would have greater contents in dry periods such as 1977-78 and 1981- 820 However, with a higher demand, Williams Fork Reservoir is more fully used for exchanges and substitution in dry years - and therefore the contents should be lower, not higher. We believe that during dry years with increased demand, GMR does not achieve a fill, therefore there can not be an exchange between WRF and Dillon because GMR is still filling. This is why WFR has higher contents. Appendix N (Table N-2) shows the STATEMOD-generated exchanges II from Williams Fork Reservoir to Dillon Reservoir. This should be compared with Table N-3 that shows the exchanges based on PAC SM. What is clear is that STATEMOD is not allowing exchanges each winter and throughout dry years. This results in higher contents in Williams Fork Reservoir, especially in dry periods, than what should be simulated. Also, for some reason, the STATEMOD-generated exchanges from Williams Fork Reservoir are unrealistic during March (Table N-2). It is also unclear whether the exchanges to the ski areas (Clinton Agreement) are being performed. We do not know how P ACSIM defines a fill of GMR - using Division 5 rules or Senate Bill 80 rules. During initial modeling, we realaized that the Williams P:\Dala\GEN\CWCB\19665\Reporl Phase 2\Technical Memorandum No. 12\Appendix B.doc 7