Laserfiche WebLink
factors as related to water being diverted by canals. Accretions and depletions from new water <br />related activities would be diverted by downstream canals as such water flows from the Front Range <br />downriver to the Colorado-Nebraska Stateline. The percent diversion loss factors listed in Appendix <br />D are gross values where lagged groundwater and surface water returns are not considered as noted <br />in Appendix D, which can result from diversions of river water used for irrigation. Colorado is <br />developing models using a Glover analysis to account for such return flows. In the future based on <br />this modeling, Colorado will present to the Governance Committee for consideration new transit loss <br />factors for routing unprotected the net accretions and depletions for determining average monthly <br />cumulative effects for mitigation purposes. <br />Cumulative Effect - Scenario A <br />Figure 1-2007 shows the results for the monthly net cumulative effect for the current year. The <br />assumptions for this analysis are those stated in CPFD approved by the Governance Committee in <br />PRRIP Attachment 5, Section 9. At the bottom of Figure 1-2007 is the percent water supply source <br />mix by region to be initially assumed as stated in the CPFD, Paragraph B. The transit loss <br />assumptions used in the Scenario A analysis are those stated in the CPFD, Paragraph C. The results <br />of this analysis show that May and June are months of net depletions (5,304 acre-feet) while the <br />other 10 months have net accretions. <br />For the year 2008 (the second year in the Initial Reporting Period), the estimated net monthly <br />cumulative effect is presented in Figure 1-2008 and reflects the additional population increase of <br />58,843 persons over the population in 2007. The results of this analysis show again that May and <br />June are months of net depletions (5,809 acre-feet), <br />Cumulative Effect - Scenario B <br />The Cumulative Effect calculation under Scenario B incorporates a reduced level of development of <br />native South Platte water sources, and a commensurate increase in the amount of water use <br />associated with reuse, than what is used in Scenario A. These proposed changes reflect the reality of <br />water use in Colorado that has occurred since the beginning of the drought in 2002. During that <br />time period, Colorado has not developed new native water sources, because junior water rights have <br />been out of priority; consequently, that source of supply has been close to non-existent and is <br />expected to continue to be a smaller component of water supply during the Initial Reporting Period <br />than what was assumed originally. Municipalities have replaced this source with increased reliance <br />on reusable water sources. Colorado anticipates that these trends will continue. Thus, development <br />of native water supplies may be significantly less than originally proposed over the next two years, <br />and reuse water supplies may continue to increase. Colorado has adjusted the assumptions regarding <br />these sources of water to better reflect the actual Cumulative Effect on the river system. Appendix <br />A is an analysis of water availability in Colorado that supports the proposed reduction in the native <br />source of water. <br />Figure 2-2007 shows the results for the monthly net cumulative effect for 2007 for Scenario B. In <br />Scenario B, Colorado adjusted its assumptions to reflect the reduced development of native water <br />supplies and an increased use of reusable water supplies. The assumptions regarding the other water <br />sources are the same as in Scenario A. The transit loss assumptions used in the Scenario B analysis