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stream flows or for natural surface water levels or volumes for natural lakes to preserve the natural environment to a reasonable degree... and; '~ § 37-92-103 (4) "Beneficial use" ... For the benefit and enjoyment of present and future generations, "beneficial use" shall also include the appropriation by the state of Colorado in the manner prescribed by law of such minimum flows between specific points or levels for and on natural streams and lakes as are required to preserve the natural environment to a reasonable degree. To implement the legislation, the Colorado Water Conservation Board (CWCB) requested the CDOW to provide the CWCB with flow recommendations which would satisfy the intent of the new law. The CDOW under § 33-1-101 (1) (CRS) is vested with the responsibility to protect, preserve, enhance and manage the wildlife and their environment for the use, benefit, and enjoyment of the people of this state and its visitors. The science of instream flows was just beginning in the early 70's. It was the CDOW's mandate to determine how to proceed, what methodology to use and what amount of flow would preserve the "natural environment to a reasonable degree". Methodology The initial method chosen by the CDOW to accomplish the task of making "instream flow recommendations" was the state-of--the-art method at the time "R2X" (a.k.a. The Sag Tape Method, USFS R2CROSS, Colorado R2CROSS). The R2X Methodology is a hydraulic based model used to predict depth, width, and velocity at modeled discharges above and below a known measured discharge. From 1973 to 1978, CDOW personnel had made several hundred flow recommendations for "minimum" stream flows to the CWCB using the R2X Methodology (Nehring 1979). These segments were mostly located in headwater reaches and at the time had little or no development potential. In the late 1970's, the U.S. Fish and Wildlife Service (USFWS), through what then was its Office of Biological Services, received funding from the Environmental Protection Agency (EPA) to establish the Instream Flow Service Group (IFSG). This group incorporated the combined talents of people from several federal and state agencies, including the CDOW. By 1979, the IFSG had completed extensive work in the field of instream flow assessment resulting in significant improvements in instream flow methodologies (Bovee and Milhous, 1978). Barry Nehring's September, 1979 Report "Evaluation of Instream Flow Methods and Determination of Water Quantity Needs for the Streams in the State of Colorado" was part of this effort. This report formed the foundation of the Instream Flow Program by identifying the critical hydraulic criteria used to determine the flows necessary to preserve the natural environment to a reasonable degree. The Nehring Report evaluated and compared several state-of-the- art instream flow methodologies including: R2X (single and multiple transects analysis), the Tennant or Montana Method and an early version of PHABSIM (IFG4). After reviewing all of the existing instream flow assessment methodologies at the time, Nehring recommended that three levels of evaluation should be contemplated to complete the monumental task of identifying and recommending instream flow values for every important stream reach in Colorado. The three levels of evaluation proposed in Nehring's Keport are discussed below: Level 1 -The R2X Single Transect Method was to be used on streams identified with low to moderate public recreation use potential and where the possibility for diversion, pollution or development was unlikely. Cited examples included headwater streams at high elevations and streams located on federally i protected lands;