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<br />33 <br /> <br />spawning and recruitment are limiting to the survival and recovery of Colorado <br />squawfish and razorback sucker in the San Juan River and throughout the Upper <br />Basin. Furthermore, enhancement of existing conditions is necessary to <br />enhance or promote spawning and recruitment. Given that existing projects <br />have significantly dewatered the San Juan River, the annual removal of an <br />additional 149,220 acre-feet of water associated with the Project further <br />reduces the probability of ever achieving necessary streamflow for future <br />maintenance and recovery of the physical and biological integrity of the San <br />Juan River. <br /> <br />Water quality <br /> <br />Surface and ground water quality in the Animas, la Plata, Mancos, and San Juan <br />River drainages have become significant concerns (Brogden et al. 1979). While <br />the selenium data collected to date may not be conclusive, potential selenium <br />contamination in project-affected rivers and newly created reservoirs and the <br />subsequent bioaccumulation in the food chain could become a problem for the <br />predatory Colorado squawfish, as well as the razorback sucker. Backwaters in <br />the San Juan River can capture irrigation return flows with inorganic selenium <br />creating a potential for selenium to be incorporated into primary producers <br />and passed up the food chain (Abell 1994). <br /> <br />Changes in water quality and contamination of associated biota are known to <br />occur in similar Reclamation projects in the San Juan drainage (i.e., <br />irrigated lands on the Pine and Mancos Rivers) where return flows from <br />irrigation make up a portion of the river flow or other aquatic sites <br />downstream (Sylvester et al. 1988). Increased loading of the San Juan River <br />and its tributaries with soil salts, elemental contaminants, and pesticides <br />from irrigation return flows could potentially degrade water quality and cause <br />harm to the endangered fishes. <br /> <br />The potential increases in selenium concentration in the waters of the San <br />Juan River caused by the proposed action could adversely affect the aquatic <br />biota of the system, including the Colorado squawfish and razorback sucker. <br />Selenium isof particular concern due to its tendency to concentrate in low <br />velocity habitats that are important habitats for Colorado squawfish and <br />razorback suckers. Operation of the Project could result in some increased <br />selenium as a result of increased irrigation return flows from seleniferous <br />soils and reduced flows in the San Juan River. Until more data are available, <br />any appreciable increase in the concentration of selenium available for <br />bioaccumulation in prey species or in whole body contamination of the <br />endangered fish species within critical habitat is considered an adverse <br />modification of critical habitat. <br /> <br />In the Service's preliminary analyses of PAH data collected from assays of the <br />San Juan River Basin, the Animas River, near its confluence with the San Juan <br />River, contained by far the highest concentrations of PAHs. Whether or not <br />this is attributable to local sources, or unidentified PAH hotspots upstream <br />in the Animas River watershed is unknown at this time. <br /> <br />Very little information is available on the influence of turbidity on the <br />endangered Colorado River fishes. It is assumed, however, that turbidity is <br />