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<br /> <br /> <br />e <br /> <br /> <br />~.. . '. <br />STATE OF COLORADO <br /> <br />Colorado Water Conservation Board <br /> <br />Depa.rtm.ent of Natural Resources <br />1313 Shennan Sltee', Room 721 <br />Denver, Colorado 80203 <br />Phone: (303) 866.3441 <br />FAX: (303) 8664474 <br />www.cwcb.state.co.us <br /> <br />MEMORANDUM <br /> <br />To: Colorado Water Conservation Board Members <br /> <br />W~@OO <br /> <br />From: Dan Merriman <br />Greg Espegren <br />Mark UppendMl <br /> <br />Date: May 11, 2001 <br /> <br />Re: CWeR Instream Flow Quantification Policy' <br />Stream and Lake Protection - Instream Flow Appropriations <br /> <br />. <br /> <br />BiJ1 OWens <br />Governor <br /> <br />Greg E. Walcher <br />Eg:ecutive DJrector <br /> <br />Rod lCuharich <br />CWCB Director <br /> <br />Dan McAuliff. <br />Deputy Director <br /> <br />. <br /> <br />Backeround <br />Colorado's Instream Flow (ISF) Program was initiated with the passage of Senate Bill 97 in 1973. With <br />the passage of that bill, the Colorado Water Conservation Board (CWCB) began appropriating ISF water <br />rights on behalf of the people of the State of Colorado to "preserve the natural environment to a <br />reasonable degree." The CWCB currently holds more than 1,800 ISF water rights covering over 8,400 <br />miles of Colorado streams, The majority of the Board's existing ISF appropriations are located on high <br />elevation stream reaches that support populations of cold water fish species, particularly trout. <br /> <br /> <br />Various state and federal agencies, as well as private parties and consultants, have provided biologic <br />instream flow recommendations to the CWCB. These biologic flow recommendations are generally <br />based on the premise that the amount of water needed to preserve an aquatic indicator species, like trout, <br />is the same amount of water necessary to preserve the entire water dependent natural environment. <br /> <br />Since the inception of the !SF Program in 1973, eWCB has considered instream flow (ISF) <br />appropriations based on a variety of quantification methods. Without question, the R2CROSS <br />methodology (Nehring 1979; Espegren 1996) has been the CWCB's most commonly used, and well. <br />accepted. quantification method. In addition, the Board has considered biologic flow recommendations <br />based on the Instream Flow Incremental Methodology (IFIM) and the Physical Habitat Simulation <br />(pHABSIM) methods, developed by the U.S. Fish aM Wildlife Service. The biologic recommendations <br />that result from hydraulic models like R2CROSS and IFIMIPHABSIM are frequently compared against <br />hydrologic m,ode)s like the Tennant Method (Tennant 1976), a.k.a. the Montana Method, for additional. <br />verification. <br /> <br />Flood Protection. Water Project Plannlng;and Financing. Stream and Lake Protection <br />Water suppiy Protection' Conservation Planning <br /> <br />