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Metropolitan Water Supply Investigation Executive Summary <br /> While each water supply category evaluated in the MWSI appears to present significant, <br /> technically feasible cooperative opportunities, each also raises several issues that present <br /> serious obstacles to implementation without considerable additional work. <br /> The table below summarizes the MWSI's findings. <br /> Cooperative Supply <br /> Category Supply or Yield Potential Actions Items/Unresolved Issues <br /> Conjunctive Use up to 60,000 acre-feet of South Platte and Blue River stream depletions <br /> surface water yield under Water right constraints <br /> example project analyzed Feasibility of long-term, large scale recharge <br /> IGA's among participants <br /> Balancing groundwater depletions with increased <br /> use of surface waters <br /> Effluent up to 120,000 acre-feet Relatively high costs <br /> of excess reusable return Public acceptance of potable reuse <br /> flows; specific project yields Effects of exchanges on water quality <br /> were not investigated Effects on instream flows <br /> Interruptible Supply up to 190,000 acre-feet Would require major institutional changes <br /> of interruptible supply; Impacts to agricultural communities <br /> specific project yields Geographic/cost considerations <br /> were not investigated <br /> Other System up to 20,000 acre-feet Water right constraints <br /> Integration of yield under example IGA's among participants <br /> Opportunities _ projects analyzed Federal action (Chatfield storage reallocation) <br /> COOPERATIVE WATER SUPPLY OPPORTUNITIES <br /> Conjunctive Use would involve the linkage of groundwater systems currently serving <br /> communities in parts of Douglas and Arapahoe counties with the Denver Water system. <br /> Water available from the Denver system in average and wet years could be used to meet <br /> demands and for recharge of Denver Basin aquifers. Groundwater sources would be used <br /> to meet demands not fully satisfied by surface water sources and during periods of <br /> drought. For the example project analyzed, conjunctive use arrangements could yield up <br /> to 60,000 acre-feet per year to meet new demands or reduce existing groundwater <br /> pumping from the Denver Basin aquifers. <br /> Conjunctive use presents a promising solution to continued dependence upon non- <br /> renewable groundwater resources by the growing communities in the South metro sub- <br /> region. Conjunctive use also raises several unresolved questions. To the extent that a <br /> conjunctive use project would rely on additional transmountain diversions from existing <br /> facilities and water rights, this would raise objections from West Slope interests. <br /> However, the operational flexibility inherent in a conjunctive use project could allow for <br /> mitigation of some impacts while still generating significant yield. Other issues and <br /> uncertainties associated with conjunctive use include changes in water rights, the <br /> feasibility of large-scale recharge over the long term, and the challenges associated with <br /> securing required intergovernmental cooperation among potential conjunctive use <br /> participants. <br /> viii <br /> Prepared for the Colorado Water Conservation Board,Colorado Department of Natural Resources by <br /> Hydrosphere Resource Consultants, 1002 Walnut Street,Suite 200,Boulder,CO 80302 <br />