Colorado River Division 5 Palisades Whitewater Park Correspondence

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velocities in the fish passage features do not meet the design criteria,the Town will be responsible for adjusting or removing project features to conform to the criteria. Therefore, adequate information to determine site hydraulic conditions with the project in place is essential. The HEC-RAS model does a good job of modeling single thread systems and the extent of inundation;however, in order to model a multi-thread system a 2-D model is more appropriate. A 2-D model will provide flow information in each channel and the velocities at each feature over 2_ v a range of discharges. Therefore,the Fish and Wildlife Service is recommending a_ D model be used to analyze fish passage at the proposed project site. We are concerned that the assumption used by Recreation Engineering and Planning(REP)that the velocity barrier created by the roughness of the channel bottom in the fish passage structures remains the same regardless of the river discharge.We believe this assumption is taken out of context from a Bureau of Reclamation report (Kubitschek 2001). In reference to the Price-Stubb fish passage project the report states that as Colorado River discharges increase the velocities along the fish passage channel appear to decrease. It then goes on to state that"this is most likely the effect of a greater percentage of the flow being passed over the 400-foot lateral rock- ramp as well as backwater effects and the increased resistance caused by increased boundary surface area." With the current information it is difficult to determine the percentage of discharge that will flow through the fish passage channels compared to the boating channels at the proposed Palisade Whitewater Park. The facilities at the Price-Stubb project are different than the proposed whitewater park, so the assumption that velocities will not increase with river discharge in the fish passage structures may not be valid. Using a 2-D model will help determine depths and velocities over a range of discharges in the fish passage structures and bypass channel. Also,the Grade Stabilization Structures (GSSs)will be creating turbulence to provide the whitewater experience,but turbulence has been documented to have significant negative impacts on fish migration patterns and bioenergetics. Turbulence is not always fully addressed in fish bypass analyses. Therefore, more information on the potential turbulence in the fish passage structures should be provided. - There are many uncertainties regarding the proposed fish bypass channel. The channel has historically been an ephemeral channel and the project would force it into a perennial channel that flows year-round. The project plan states that 40 cfs will flow down the fish bypass channel at all times. What design features will force more water into the bypass channel and how will you predict the percent of river discharge that flows into the bypass channel? The project plan calls for"near vertical sides". A stability analysis should be conducted before this design .criteria is accepted. The Bureau of Reclamation prefers a 1:1.5 slope for usual sizes of lined canals. The substrate particle size in the bypass and suspended loads should be identified and the design should minimize erosion and minimize deposition in the bypass channel. These analyses are often conducted using Regime Equations or a similar analysis. With the proper design the bypass channel should meet the fish passage depth and velocity criteria. However,it is unknown if fish will use the fish bypass channel. Very little is known about the behavior of the Colorado River endangered fishes, because of turbid river conditions, direct observation is not possible. Fish passages at dams within critical habitat on the Colorado and Gunnison rivers have specific 7