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o ;-:~ c." 8 ~ c' <>. ') o In determining specific river reaches required to prevent extinction and ensure recovery of the Colorado squawfish, the Service relied upon available biological information and the species' approved Recovery Plan (U.S, Fish and Wildlife Service 19911. Information relating to the species' biological and ecological needs, such as habitat, reproduction, rearing, and recruitment, was used in determining if en aree WI!S needed for Inclusion In critical habitat. The revised Colorado Squawfish Recovery Plan provided both downlisting and delisting criteria. During the consideration of critical habitat areas, downlisting criteria were generally equated to the survival level; delisting criteria were related to the recovery level. The reach of the San Juan River from Lake Powell to Farmington, New Mexico, which incorporates the section of the river encompassing the project facilities and impacted by their presence and operation, was included in the Recovery Plan as necessary for both downlisting and delisting. Therefore, this portion of the San Juan River has been identified by the Service as essential to the survival and recovery of the Colorado squawfish. C. PROPOSED AREA The San Juan River and its tributaries form the second largest of the three sub-basins comprising the Upper Colorado River Basin. The San Juan River drains about 38,000 square miles of southwestern Colorado, northeastern Arizona, northwestern New Mexico, and southeastern Utah. From its origins in the San Juan Mountains of Colorado, the San Juan River flows some 31 miles to the New Mexico border, 190 miles westward to the Four Corners area, and thence another 136 miles to Lake Powell. In its upper reaches, the river traverses rugged terrain and has a relatively high gradient. The river emerges from canyon- bound reaches shortly after entering New Mexico and flows through a broad floodplain for much of its course in New Mexico and Utah. About 70 miles upstream of Lake Powell, the river again enters canyon reaches for the remainder of its course. The river is generally restricted to a single channel in canyon portions, but is often divided into several channels in floodplain reaches. The San Juan River has comparatively few perennial tributaries, most of which are in upper reaches. Historically, the Pinos, Piedra, Navajo, Animas, La Plata, and Mancos rivers, Rio Blanco, and McElmo Creek were the only perennially flowing tributaries. Other streams such as Montezuma and Chinle' creeks seasonally contributed flows. Numerous washes and arroyos also entered the river, but none provided regular flow. Among tributaries, the Animas River contributed the greatest flow. The five stocking sites selected for the proposed stocking of the Age-O fish were chosen based on the delineation of distinct geomorphic reaches within the San Juan River. Eight such reaches have been identified by Bliesner and Lamarra (1995) in the San Juan between the two major features that essentially define'the river for the purposes of conservation of the COlorado,squawfish: Lake Powell at the downstream terminus of flowing water. and Navajo Dam at the upstream control of flows in the river, The eight distinct reaches were screened through several data sets within the categories of: river valley width, channel contact geology Imaterial in cut-banks & bedrock contact). riparian vegetation, channel gradient, channel pattern (braiding and sinuosity). tributary influence, anthropogenic influences (diversion dams, irrigation, levees, etc.) and aquatic habitat (six categories at three flow rates). Utilizing these categories, the fOllowing reaches of the San Juan have been identified (by River Mile [RM]):