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temperature. The average daily water temperatures would rise under these conditions and the daily water temperature cycle would be exaggerated. • The computer model could be easily modified to include the maximum daytime water temperature model.. CONCLUSIONS In general, the Green River reaches offered more physical habitat for squawfish YOY than did those on the Colorado River. Also, at the Black Rocks and Potash reaches, considerable YOY habitat was available across a broad range of flows. Considering the downstream location of the Potash reach, it was advantageous that higher flows there were required to provide maximum squawfish YOY habitat. Squawfish YOY habitat at the Potash reach was highest between 7,000 and 10,000 cfs and again at 15,000 cfs. At Black Rocks humpback chub adult habitat was insensitive to changes in flow with high WUA at low flows increasing as flow increased. The Green River reaches did not respond similarly to changes in flow. First, maximum squawfish YOY habitat at the Mineral Bottom reach was attained at a lower flow than that which provided maximum YOY habitat at the upstream Ouray reach. Second, at all Green River reaches, either very low YOY habitat (at Grey's Canyon) or appreciable habitat across only a narrow range of flows was demonstrated. At the identified nursery sites (Ouray and Mineral Bottom) flows in the 2000-4500 cfs range were • most suitable for squawfish YOY. At Mineral Bottom, this range was restricted to less than 3500 cfs. In contrast, at the Moab and Greys Canyon reaches, very little habitat was available at any discharges except those within an extremely narrow range. The results presented here may be used to formulate certain hypoth- eses regarding the effects of changes in discharge, especially upon preferred habitats of Colorado squawfish YOY. They should not be con- strued as flow recommendations or standards against which projects should be evaluated. Within the limitations of the data it is possible to make some valuable conclusions. 1. To a low discharge level of 2000 cfs, changes in dis- charge at the Black Rocks reach of the Colorado River do not cause significant changes in available physical habitat for or adult humpback chubs. 2. At the sand-substrate reaches, such as the Moab, Ouray and Mineral Bottom reaches, changes in discharge within the normal range may have profound results upon available physical habitat, especially for squawfish YOY. Because these reaches have been identified as prime habitats for rearing of squawfish young, and because they represent a • very prevalent UCRB habitat type, it would seem highly 32