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0 River demonstrate the feasibility of recreating backwaters using existing riverine features. These side channels serve as backwaters as water levels rise in the spring. They drain naturally with descending flow and do not become refugia for predaceous or competitive non-native fishes. Side channels in areas identified for stocking adult razorback sucker in the upper Colorado River could be modified and enhanced similar to resemble those that naturally exist to that on the Yampa River. The upstream end of the side channel could be diked with earthen material and reinforced with rock rip rap. Man-made water structures could be placed at the up- and downstream end to control water volume and flow so that sediments could be flushed during high water as needed. If it is necessary to control the migration of fish in and out of the created backwater, a fish trap could be installed at the downstream end. With this design, razorback sucker would use modified side channels only during high flow periods. Side channels located near or within a stocking area could be designed and operated to serve as perennial rearing units for razorback sucker. Hydrologists would first be consulted to determine if the use of such a side channel was feasible. The sides of a side channel selected would have to withstand over-bank flooding to prevent premature escape of fish. Earthen material and water control structures would be placed at the up- and downstream ends of the side channel. The side channel could be flooded naturally with high spring flows or regulated by water control structures. 10 During low-water periods, occasional pumping from the river may be required to maintain water levels in the rearing unit. Following removal of all undesirable fishes, young razorback sucker could be stocked, reared to the desired size and subsequently released into the river. Fish could be released 25 10