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3.0 Scientific Basis And Underlying Principles The fifth and sixth principles are based on the "reset theory" of floodplain management, which allows floodplains to inundate and remain flooded for at least 2 years, then desiccate. This "reset theory" serves the fundamental ecological functions of providing connectivity for fish entrainment and movement, stimulated floodplain production, and periodic desiccation to reduce effects on nonnative fishes. This "reset theory" has not been thoroughly tested, but research on various components of the strategy indicate a high probability of success. 3.3 Green River Flow Recommendations 3-3 April 2004 Ecological functions of "reset theory" 1. Periodic inundation allows access to drifting larval razorback sucker and escapement of adults, 2. Periodic inundation/desiccation stimulates food production and freshens water quality, and 3. Periodic desiccation strands and kills nonnative fishes Flow recommendations for the Green River downstream of Flaming Gorge Dam (Muth et al. 2000) are designed to be implemented, evaluated, and revised according to findings of scientific investigations and through NEP A and ESA compliance. Flow recommendations are made for summer through winter base flows and for spring peaks for each of three longitudinal river reaches, and are based on five hydrologic conditions that reflect annual river volume (Table 3-1). The basis for the general recommendation is that peak flows should be of the magnitude, timing, and duration to provide floodplain inundation in the Ouray reach for at least 2 weeks in 4 of 10 years and at least bankfull flows in 1 of 2 years. Under average hydrologic conditions (30-70% peak exceedence), 18,600 cfs (527 m3/s) should occur in 1 of2 years and be maintained for at least 2 weeks in 1 of 4 average years. Average peak flow ofthe Green River near Jensen (RM 316), 56 years of record through 2000 (pre- and post-Flaming Gorge), is 19,706 cfs; this is the instantaneous peak and does not reflect duration. Area of floodplain inundation for different river flows was determined for portions of the middle Green River using a HEC-2 step backwater model (F10 Engineering 1996). This model determined that for existing conditions (without levees removed) in the Ouray reach (River Mile [RM] 252-265), the area of floodplain inundation increases rapidly at flows exceeding about 18,600 cfs (Figure 3-1). With existing levees removed, flooding in the Ouray reach would be initiated at 13,000-16,000 cfs resulting in about 5,400 acres of floodplains. Similar relationships were found from aerial photography for existing conditions from Pariette Wash to Split Mountain (Bell et al. 1998). The majority ofthese floodplains are terraces that fill and drain with river stage and may not hold water and fish for long time periods and therefore, may not currently be suitable nurseries for razorback sucker. Relationship of flow to floodplain area from Pariette Wash to SpIt Mountain (240- 319; Bell et ale 1998) . 5,904 acres at 20,000 cfs 9,550 acres at 22,000 cfs 13,927 acres at 25,000 cfs . .