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12 criteria. Based on the all available information, the changes to the preferred alternative between the draft and final EIS would not result in a significant long-term impacts. The magnitude of any impacts that do occur would likely be less than that caused by the variability in tributary flow. Some individuals have asserted that changing both the upramp rate and the maximum flow constraint at the same time is a poor experimental design. Viewed from the purely scientific viewpoint, it would be better to change variables one at a time in a controlled experiment. However, there are already many uncontrolled variables, and the interests lie in measuring the possible resource impact, if any, which might result from jointly changing both criteria. As described in this document, the best available information indicates that the long-term impact of changing both criteria at once will be difficult, if not impossible to detect. Even though both parameters would be changed at the same time, for 8 months of an 8.23 maf year only the upramp would be used. The ability to operationally exceed 20,000 cfs only exists in months in which releases are in excess of 900,000 acre feet. In a minimum release year, the most probable months that increases above 20,000 cfs would occur are December, January, July and August. Evaluation of the upramp rate effects can be initiated immediately with evaluation of. the increases in maximum flow relegated to the months with the highest volumes. The changes in operations discussed above will be monitored as part of the Adaptive Management Program, and future changes in operations will be made if the scientific evidence supports it. VI. LITERATURE CITED Ayers, A.D. and T. McKinney. 1995. Draft Final Report. Effects of different flow regimes on Periphyton standing crop and organic matter and nutrient loading rates for the Glen Canyon Dam Tailwater to Lees Ferry. Glen Canyon Environmental Studies, Report WAQ0300. Arizona Game and Fish Department. Beus, S. and C. Avery. 1993. The influence of variable discharge regimes on Colorado River sand bars below Glen Canyon Dam. Glen Canyon Environmental Studies, Report PHYOI0l, Chapters 1 through 7. Northern Arizona University, Flagstaff, AZ Beus, S., M.A. Kaplinski, J.E. Hazel, L. A. Tedrow, and L. H. Kearsley. 1995. Monitoring the effects of interim flows from Glen Canyon Dam on sand bar dynamics and campsite size in the Colorado River corridor, Grand Canyon National Park, AZ. Glen Canyon Environmental Studies, Report PHY 0112. Northern Arizona University, Flagstaff, AZ Budhu, M and R. Gobin. 1994. Monitoring of sand bar instability during the interim flows: a seepage erosion approach. Glen Canyon Environmental Studies, Report PHY 0400. University of Arizona, Tucson, AZ