Cumulative Effect Report on Plan for Future Depletions

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Original Assumptions With Suggested Adjustments Year Total Annual Accretions less depletions May-June Total Annual Accretions less depletions May-June 2007 +28,255 acre-feet (afl -5,304 af +26,582 af -2,713 af 2008 +30,946 acre-feet -5,809 af +29,114 af -2,972 af Colarado has begun to make the required Mary-June replacements by pumping Tamarack State Wildlife wells and leasing excess May-June augmentation plan recharge credits from private parties. Transit loss assumptions contained in the Plan for Future Depletions do not accurately reflect physical flow conditions and the Governance Committee should adjust those assumptions in the future. Colorado will propose a transit loss adjustment to the Governance Committee later this year. Colorado has not included adjustments to transit losses in the calculations made in this report. Backeround Paragraph E states that the calculation of the average monthly distribution of the Cumulative Effect will be based upon the projected Population Increase and the water use and transit losses described in the document, or as mav be modi aed bv the Governance Committee. This report for the Initial Reporting Period includes two separate calculations of the Cumulative Effect. The first calculation uses the original assumptions contained in the CPFD, and is referred to as Scenario A. The second calculation is a more accurate estimate of the actual Cumulative Effect, and is referred to as Scenario B. Scenario B reflects a significant change in the hydrologic river regime in Colorado that has occurred since 1997 due to a severe drought and increased water regulations impacting junior water rights. Colorado proposes to adjust the assumptions that go into the calculation of the Cumulative Effect for the Initial Reporting Period to reflect this new hydrologic river regime. As provided in Paragraph E, Colorado requests the Governance Committee to consider and accept a different calculation of the Cumulative Effect that Colorado feels is a more reflective and accurate estimate of the actual Cumulative Effect which will be mitigated by Colorado for the Initial Reporting Period. As mentioned above, this Report includes a letter report from the Colorado State Demography Office as required by Paragraph A of CPFD. This population information is inserted into the CPFD spreadsheet to compute net accretions and depletions (e.g. Cumulative Effect, for those two years). This report lists a population increase of 676,697 from July l, 1997 to January 1, 2009 or for this 11.5-year period, an annual population increase of 58,843 per year. The projected population increase used in the spreadsheet for 2007 is 617,854 (July 1, 1997 until January 1, 2008), while the population increase used in the spreadsheet for 2008 is 676,697 (July 1, 1997 until January 1, 2009). Finally, the transit loss assumptions in the CPFD in Paragraph C are based on the administrative losses assigned by the Colorado State Engineer for routing reservoir releases downriver (i.e., protected flows). Colorado wants the Governance Committee to be aware that they are studying new transit loss factors that better reflect the physical situation of water flowing downriver subject to re-diversion and subsequent return flows (i.e., unprotected flows). The Water Conservation and Water Supply Study dated December 1999 of the Platte River Research Cooperative Agreement contained Appendix D written by the Water Management Committee, which dealt with monthly loss