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26 resulting in a narrowing of the channel with reduced flood capacity (Bliesner and Lamarra 1994). 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. Bald eaale The existing habitat in the project area consists of the Animas, La Plata, and Mancos Rivers and their attendant riparian zones. Fish and waterfowl from these river systems provide a prey base for wintering eagles. Upland areas, some of which may be converted to agricultural lands with project implementation, contribute to the prey base used by bald eagles. Reclamation (1995) reported mule deer, prairie dog, and rabbit as components of bald eagle diets in the project area. Reclamation reported that habitats receiving the highest use during the day in the winter are cottonwood dominated plant communities with large mature trees and adjacent emergent wetlands, where human development is minimal. Isolated cottonwood trees outside the riparian zone, such as those associated with irrigation canals, also provide habitat for bald eagles. Three bald eagle breeding territories occur in la Plata County, Colorado. One is located on the Animas River, but it has not been active since 1979. The other two are north of the project area and have been active in recent years. One is in the vicinity of the Animas-la Plata Project, approximately 4 miles from Ridges Basin, west of Perins Peak. The pair of bald eagles are often observed collecting prey at Lake Durango and a fish hatchery on lightner Creek. If Ridges Basin were constructed, it would likely provide a prey base for these birds (Scott Wait, CDOW, pers. comm., Jerry Craig, CDOW, pers. comm.). Because Ridges Basin Reservoir (when not frozed) would likely provide a prey base for nesting and wintering bald eagles, the Service finds that potential water quality problems or bioaccumulation of contaminants may affect bald eagles. Soil extracts from Ridges Basin show several sites with selenium concentrations well above any of the aquatic life criteria. Soil extracts represent the soluble fraction of materials in the soils under laboratory conditions. The safe levels of selenium concentrations for protection of fish and wildlife in water are <2.0 ~g/l and toxic levels are considered >2.7 ~g/l (lemley 1983, Lemley and Smith 1987, Maier and Knight 1994). On the north side of the proposed reservoir basin, soil extracts had a concentration of 24 ~g/l of selenium and a concentration of 60 ~g/l of selenium was found on the south side.