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<br />- ________n ____ <br />:11 <br />~~ <br />~' <br /> <br />I <br /> <br />~ <br /> <br />25 <br /> <br />"~ <br /> <br />The Project will cause discrete, identifiable, additive, adverse impacts to the <br />San Juan River endangered fishes. As shown in the flow analysis, the Project <br />will cause flow depletions which, in addition to existing projects, will further <br />alter historical flow regimes. <br /> <br />Since 1963, the operation of all existing projects, especially the Navajo Dam, <br />has significantly altered flows of the San Juan River resulting in a decrease in <br />average spring peaks and a doubling of average winter base flows. The Project <br />would further reduce the remaining spring runoff within occupied habitat. Not <br />cDincidentally, as shown in Tables 1 and 2 of Appendix B, in 1987, when spring <br />peaks were similar to historical levels (pre-Navajo), the highest reproduction <br />ever documented duri ng the 3 years of study for Colorado squawfi sh occurred in:: <br />the San Juan River (Platania 1990). In 19B8, when only one young-of-year <br />squawfish was captured, and in 1989 when no young-af-year squawfish were <br />captured, spring peaks as well as other flows were even lower than the current <br />(post-Navajo) average conditions, <br /> <br />The fact that the Project would further deplete flows during peak runoff is of .c <br />concern to the Service because this period is of great significance <br />geomorphically and ecologically. This is the most dynamic period in the cycle, <br />and it precedes the very critical spawning period of the endangered fishes. <br />Observations clearly demonstrate that the spawning activities of these fish are <br />synchronized with and are undoubtedly influenced by the spring runoff period <br />(Archer et al. 1986, Archer and Tyus 1984, Tyus and Karp 1989). The Service <br />believes that peak spring flows are very important for maintaining channel <br />geomorphology, providing access to off-channel habitats, stimulating spawning <br />migrations, and preserving suitable spawning substrates. <br /> <br />While the precise volume and duration of flows required for maintaining and/or <br />improving important physical and biological needs are unknown, it appears that <br />spawning and recruitment are limiting to the survival and recovery of Colorado <br />squawfish in the San Juan River and throughout the Upper Basin. Furthermore, <br />enhancement of existing conditions is necessary to enhance or promote spawning <br />and recruitment. Given that existing projects have significantly dewatered the <br />San Juan River, the annual removal of an additional 154,800 acre-feet of water <br />associated with the Project further reduces the probability of ever achieving <br />necessary streamflow for future maintenance and recovery of the physical and <br />biological integrity of the San Juan River, <br /> <br />High concentrations of heavy metals, selenium, and hydrocarbons have been found <br />in the fish and birds collected by the Service in the San Juan River Basin <br />(Department of Interior Intensive Desk Evaluation of Irrigation Drainage 1989). <br />The knowledge of the effect of the Project on the concentration of these <br />elements is limited and needs to be studied as part of the research, Of <br />particular concern to the Service is the potential for increased bioavailability <br />of heavy metals and selenium associated with the San Juan River Basin. <br /> <br />