2010-11-22_REVISION - M2009023 (7)

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Biological Environment Food supply, predation, and competition are important elements of the biological environment. Food supply is a function of nutrient supply and productivity, which could be limited by the presence of contaminants. Predation and competition from nonnative fishes has been identified as a factor in the decline of the endangered fishes. Depending upon species-specific tolerance levels, nonnative fishes may have competitive advantages in habitats damaged by the presence of contaminants and altered flow regimes. EFFECTS OF THE ACTION Factors to be Considered Water depletions contribute to reductions in the Colorado pikeminnow and razorback sucker populations. Other major impacts are dams, competition and predation from nonnative fishes, changes in flow and temperature regimes, changes in river channel morphology, and increased selenium levels. The reductions in population and habitat warranted listing these species as endangered. In response to listing, the Service, and other Federal agencies have implemented actions to conserve the species and encourage recovery. One such action is the reoperation of Navajo Dam to mimic the natural hydrograph by following the San Juan River flow recommendations (Holden 1999). Meeting the flow recommendations is expected to provide flows through designated critical habitat which will ensure the survival and promote recovery of the Colorado pikeminnow and razorback sucker. However, until a biological response is - detected according to the criteria developed by the San Juan River Recovery Implementation Program's Biology Committee, the success of meeting the flow recommendations will not be known. Analvses for Effects of the Action Water Quantity Water depletions cause discrete, identifiable, additive, adverse impacts to the Colorado River endangered fishes. The proposed action will result in a new average annual depletion of 1,535 acre-feet from the San Juan River below the confluence of the La Plata River. In order to determine if the San Juan River flow recommendations can be met with the proposed project in place, proposed operations of Long Hollow Reservoir were entered into the San Juan River Flow Recommendation model. Results of the model run demonstrate that with the proposed project in place, the San Juan River flow recommendations can still be achieved. The model run was conducted by the Bureau of Reclamation (Riverware Version 4.4, Data Set 2.6) and the results are presented in Appendix A. The model run results show that all primary and secondary flow recommendation criteria are met Water Quality The proposed new reservoir will be filled with water from Long Hollow Creek, which consists primarily of irrigation return flow from Red Mesa. Selenium concentrations can be elevated in areas where irrigation occurs on soils which are derived from or which overlie Upper Cretaceous 25