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t r~ Level 2 -The R2X Multiple Transect Method was to be used on streams identified with moderate to above average public recreation use potential and where the possibility for diversion, pollution or development was likely. Cited examples included streams or rivers which supported moderate to above average uses for fishing, kayaking, rafting and other types of outdoor recreation; and Leve13 - PHABSIM/IF'IM Method was to be used on streams identified as critical to the State of Colorado and/or the Federal Natural Resource Agencies. These streams have been identified with above average public recreation use potential and where the possibility for diversion, pollution or development was likely or already occurring. Cited examples included the Fryingpan below Ruedi Reservoir, South Platte River below Cheesman Dam, Gunnison River upstream from Hotchkiss, Rio Grande River upstream of Del Norte, Cache la Poudre River, North,Platte River and the Blue River. In addition streams with endangered, threatened or species of special concern should be considered for this methodology when possible. Initial Instream Flow Recommendations Criteria for minimum flow determinations identified in the 1979 Nehring Report included the three key flow parameters we use today: Average Depth (feet), Averal;e Velocity (feet per second) and Percent Wetted Perimeter. If these parameters are maintained at or above minimum acceptable levels across a riffle, they will be maintained at acceptable levels in other habitat types such as pools and runs. The report states "Instream flow recommendation(s) in cfs are selected when minimum levels of two or more parameters are reached within the designated stream class." According to the contract with the USFWS, the CDOW was to provide "Monthly water quantity needs .for fish and wildlife populations ..."; however, in 1979, it was felt that multiple monthly flow recommendations would not. be accepted or if they were accepted by the CWCB, they would not be enforced (Nehring 1979). CDOW's initial • instream flow recommendations reflected this thinking, in that minimum stream flow recommendations during this time period consisted of only single year-round flow amounts. Prior to 1981, instream flow recommendations were not adjusted downward due to a water availability standard. It was not until the State Legislature passed Senatf; Bi11414 in 1981 that instream flow appropriations would require an evaluation of the existing physical water supply or a water availability analysis. Also during this time period, existing instream flow assessment methodologies were being refined and new methodologies were being developed. These advancements in instream flow science revealed that varied flow regimes were critical to river health. Research has shown that single year- round minimum flows, when maintained as a long-term condition, cannot be expected to sustain the same fish populations or aquatic life as a natural flow regime;, where low flow conditions occur infrequently and for shorter :periods (Stalnaker and Wick 20C10). Along with this new requirement to perform a water availability analysis came the recognition of the need and the ability for the CWCB to accept and enforce seasonal and/or monthly flow recommendations. To incorporate the latest science and the :resulting change in policy, CDOW biologists modified their original instream flow methodology of recommending "minimum" single stage year-round flows to recommending "minimum multi-stage instream flows" to more reasonably meet the needs of the natural enviromnent. This change resulted in "seasonal flow recommendations" which incorporated all three of the critical criteria identified by Nehring in his 1979 Report. These seasonal flow recommendations are an attempt to protect a varied flow regime and reasonably mimic, on a simplistic and much smaller scale, a stream's natural flow regime, taking into consideration water availability constraints2. ~ It is notable to point out that the Attorney General's opinion regarding water availability was that if the recommended instream flow value was ever physically available, then legally, the instream flow recomtnendation was available for appropriation. However, the CWCB developed a more conservative and reasonable standard regardinf; water availability, adopting a median or average flow standard for the basis of a water availability analysis.