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.<'~! ,- ~.--_:{:I -....:1' The maximum release of the test flow is not to exceed 1275 cms which is within the capacity of the Glen Canyon Dam powerplant and jet tubes. Releases greater than this would have required use of the spillways and create a potential for introduction of nonnative fishes from the Lake Powell. In addition to the obvious concerns for introduction of reservoir fishes into Grand Canyon. by not using the spillways, determining the affect of test flows on nonnative fishes in the Grand Canyon will be easier without the confounding influences that might occur if there another source of unknown nonnative fishes in the system. The ramping of flows from 226 cms to 1275 cms will be accomplished at a rate of 113 cms/hour and down-ramping will decrease in a stepped pattern, beginning at 43 cms/hour and diminishing to 15 cms/hour. As down-ramping has more potential to degrade beach and sandbar faces, the pattern selected will assist in maintaining the newly deposited sediments. The extent that new return current channels and backwaters created by the 1275 cms flow will be available to fishes when operations return to normal (interim operations) is not known. While there has been considerable study of the Colorado River and the Grand Canyon ecosystem, the ability to accurately predict consequences of even a managed flood flow requires additional effort represented by the study component of the proposed action. The critical habitat primary constituent elements of physical habitat and biological environment' should be benefited by the test flow for the humpback chub. Particularly, nursery, feeding, and rearing areas should be restored for young-of-year and other sub-adult humpbaclc chub in the mainstem by supplying an increase in sediment to the nearshore areas. Predation and competition from nonnative fishes might also decrease if those species are more disadvantaged by high flow. Kanab Ambersnail This is a re-consultation on the known population of the Kanab ambersnail in Grand Canyon which will be affected by the proposed project. The first consultation resulted from the December 1994 biological opinion issued by the Service on the operations of the dam that concluded that incidental take will assume to be exceeded if more than 10 percent of the occupied habitat were inundated. The proposed action anticipates that between 11.8 to 16.1 percent of the habitat will be destroyed (Table 1). High flows will result in inllndation, scouring and destruction of habitat. Habitat that is not destroyed may be flushed altering ambient soil moisture. litter, species composition or density. or other factors needed to maintain the Kanab ambersnail. The Kanab ambersnail distribution is strongly correlated with the presence of Mimulus. Nastunium, and other species of vegetation associated with primary habitat. The loss of this habitat will adversely affect the population. The analysis of habitat inundation is based on the Stars Model, a reach averaged standard step hydraulic model. This model has approximately 0.5 m of error at the 1275 cms line, indicaling that the actual zone of inundation may be 21.6 m" less or 24.37 m2 or more than anticipated Biological and Conference Opinions Glen Caoyon BeachlHab'la,-Bull11ing Flows 2116196 18