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Climate change over the coming decades and centuries has the potential to affect many <br /> organisms, including freshwater fish. EPA (2015) discussed a change in precipitation patterns, <br /> including the timing, intensity, and type of precipitation received; runoff patterns based on the <br /> amount of precipitation falling as snow and when snowmelt occurs; and atmospheric <br /> temperatures,which exhibit a strong influence on water temperatures. <br /> According to the National Research Council (2012), air temperature has increased by 1.4°C in <br /> the last century. The Colorado River Basin has warmed more than any other part of the U.S. <br /> (Service 2015b). Drier conditions,warmer air temperatures, and earlier spring runoff peaks are <br /> expected to affect water availability and the quality and quantity of fish habitat,which are <br /> important elements to native fish in action area. It is impossible to predict with any degree of <br /> precision,however,to what extent endangered fish and their habitats will be affected. <br /> However, given that these endangered fish live in main-stem rivers, generally downstream from <br /> most of the dams on tributaries within the Upper Colorado River Basin, it is possible that some <br /> of the effects of climate change in the area could be moderated by dam releases, particularly if <br /> they are done to benefit endangered fish. For example, earlier snow melt and runoff in upper <br /> tributaries would influence stream levels above downstream dams,but downstream flows are <br /> controlled by dam releases. Warming water temperatures would be counteracted to some extent <br /> by cold water releases from the base of a dam. These endangered fish are not cold water <br /> dependent fish; cool water temperatures may be more limiting to some or all of them than warm <br /> water temperatures (on the up-river limits of their distribution). Higher summer-time base flows <br /> as a result of dam releases also work to keep water temperatures from climbing as high as they <br /> otherwise would under lower flows. Most or all of the reaches occupied by these endangered <br /> fish are influenced by upstream dams. <br /> These dams,whether main-stem dams or on up-basin tributaries,have numerous negative effects <br /> on the endangered fish and their habitats. However, in the face of a warming and drying climate, <br /> some of the potentially negative effects of climate change (e.g., change in timing of runoff,water <br /> temperature increase, drop in base flows) could be ameliorated by dam releases. Alternatively, <br /> some of the negative effects of existing dams may be ameliorated by climate change (e.g., <br /> warming of below-dam cold waters, a lower water level in Lake Powel resulting in the eventual <br /> emergence of more potentially habitable river miles on the Colorado and San Juan Rivers). <br /> Aside from the interaction of dams and climate change, increasing water temperatures could <br /> potentially extend suitable habitat for one or more of the endangered fish (non-canyon bound <br /> species)up river into what may currently be too cold. <br /> See also Climate Change in the Action Area(section 3.4)within the Baseline below. <br /> 3.0 ENVIRONMENTAL BASELINE <br /> The environmental baseline includes the past and present impacts of all Federal, State, and <br /> private actions and other human activities in the action area; the anticipated impacts of all <br /> proposed Federal projects in the action area that have already undergone formal section 7 <br /> consultation; and the impact of State or private actions contemporaneous with the consultation <br /> process. <br /> 33 <br />