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relationships among these causes of erosion? Cumulative impacts? Tradeoffs? " "( Pg. 97, C. 1, P. 1. The EIS should explain why the USBR supports the National Park Service reluctance to employ non-operational alternative beach stabilization techniques. Reasons given are: 1) rock is not always available; 2) alternatives to rocks may not work; or 3) structures may not be allowed within the "proposed" wilderness area. Also, why has the National Park Service rejected a proposed USBR demonstration project to determine the feasibility of dredging sand from pools to create more sandy beaches? This method promises to be far less intrusive than flood releases. There is no indication recreational use of the river corridor by rafters or hikers would diminish if all sand beaches were lost even though campsites might be relocated. Where is this issue discussed and how does this affect your choice of alternative? Pg. 103 , C. 2, P. 3 . Both nitrogen and phosphorus loads are reduced in reservoirs from their inflow values which changes the location primary (algae) production occurs and makes less nutrients available below a dam. Below the dam, the overall trend shows N also decreasing, being about 1/3 of pre-dam concentrations. Less P is needed now to use all available N and we don't know where this relationship will stabilize. You should more fully explain the relationship of P with intake depth. Also, are you suggesting a change in intake elevation would enhance P availability downstream? If N is reduced, what difference would this make to stream productivity? ,. ) ..~ ;;.' .,j. " "". Pg. 104, C. 2, P. 1. Algal productivity below the dam is now higher than ever. Since energy contribution to the lower canyon river occurs as a result of fluctuating flows (enhances it), how would a change in flows be better? Would the steady flows decrease organic contributions to the lower river if less is entrained? '. ,. \ v Desert rivers like the Colorado cannot rely on the sparse riparian vegetation as a source of fixed energy but instead must generate its own energy from within which attaches more importance to the increased algae production in, the clear water below dams when compared with pre-dam. Areas downstream of dams which remain turbid also have higher production after dams due to greater production in clear portions feeding fixed energy ( adding fuel ) to downstream areas. More explanation of energy transfer by the aquatic system is needed to justify changing from present conditions to some other pattern which may reduce food supplies downstream. .~:' :i.' :-<:~ ~ /'. .-,. ...... Pg. 105, C. 1, P. 1. The algae standing crop may increase but the growth rate would drop. Sloughing of algae would decrease, thereby decreasing energy transfer downstream to less productive (more 21