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31 fishes. The Service concludes that water depletions impact the primary constituent elements, Water Quanti tv The Project will cause an average annual depletion of 13.485 acre-feet. Existing annual water depletions from the project are estimated to be less than 5.500 acre-feet. As the West Slope marketing plan is implemented annual depletions will increase. Wolford Mountain Reservoir operations will cause reductions in flow in the Colorado River during spring runoff when the reservoir is storing water. With the exception of early season releases. bypasses for flood control and participation in the Combined Reservoir Qperation Program, the reservoir is generally operated in a fill and spill manner. This means that much of the first water available is stored in priority. and when the reservoir is full, the amount of inflow passes through the outlet works over the uncontrolled spillway. Normally. when flows on the Colorado River are peaking, Muddy Creek inflow is receding and diversions to storage have either ceased or are at a lower level. The reservoir typically spills in May. prior to peak runoff in the Colorado River. A slight increase in flow is anticipated for other times of the year. Table 3 displays the change in stream flows in the IS-mile reach with full project implementation. The project will cause discreet, identifiable, additive impacts to the Colorado River endangered fishes. A cumulative effects flow analysis was conducted for the 1990 biological opinion that showed the project will cause additional flow depletions and additional changes in historic flow regimes in combination with other existing and planned water projects. Table 3 updates the "with project" hydro I ogy from the 1990 bi 01 ogi ca 1 opi ni on. The fact that the Wolford Mountain Project depletes flows during spring runoff is of concern to the Service because this period is of great significance geomorphically and ecologically. This is the most dynamic period in the hydrologic cycle. Observations clearly demonstrate that spawning activities of these fishes are synchronized with and are influenced by the runoff period (Archer et al. 1986). Spring flows are very important for maintaining channel geomorphology. providing access to off-channel habitats, and preserving suitable spawning substrates. Kaeding and Qsmundson (1987) noted that the majority of adult Colorado squawfish were captured in gravel pit ponds which are only accessible during the high flow period. These findings are consistent with spring Colorado squawfish captures throughout the Green and Colorado River basins (Archer et al. 1986). Colorado squawfish appear to seek out flooded backwater type habitats in the spring because of their warmer temperature and abundant