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Executive Summar April 23, 2003 <br />Page iii <br />The study incorporated the following types of information for purposes of evaluation of <br />impacts: <br />? Colorado Water Conservation Board (CWCB) instream-flow water rights <br />? Minimum and optimum fish flows <br />? Low, high and optimum kayaking flows <br />o Low, high and optimum rafting flows <br />o Reservoir levels necessary for boat ramps and marinas <br />? Wastewater treatment plant 1-day and 30-day, 3-year low flows <br />The CWCB instream-flow rights are of interest because they limit junior water diversions <br />and represent the minimum flows necessary to protect the environment to a reasonable <br />degree subject to water availability. The modeling explicitly accounted for these <br />instream-flow water rights. <br />The fish, kayaking, and rafting flows and reservoir levels are guidelines that the study <br />established based on information from Colorado Division of Wildlife (CDOW) and local, <br />established guides and businesses. The flows and reservoir levels represent what the <br />recreation and in-basin communities believe is important to sustain a quality recreational <br />expenence. <br />The wastewater treatment plant information provides an indication of potential water <br />quality impacts in streams below wastewater treatment plants. Wastewater treatment <br />facilities' discharge permits depend on certain minimum stream flows for determining the <br />quality and quantity of the wastewater that can be discharged to the stream. If stream <br />flows drop too low, then wastewater treatment plants may be required to provide <br />additional treatment, forcing expensive treatment plant modifications. <br />Denver Water Needs <br />Under the PACSM scenarios evaluated in Phase II, at full use of the existing system the <br />average annual Roberts Tunnel diversions will increase by about 64% from 70,500 acre- <br />feet of existing demand to 115,400 acre-feet. This increase will occur as demand in the <br />Denver Water service area grows without building new facilities. In addition to the 64%, <br />if the next project on line were a North System supply with a firm yield of 15,000 acre- <br />feet, diversions from Summit County would increase by 3% to 118,600 acre-feet. If the <br />next project on line were a South System supply, the diversions from Summit County <br />would increase by an additional7% to 123,400 acre-feet. <br />Hydrosphere, 1002 Walnut Suite 200, Boulder, CO 80302