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a 28 period of record occurs almost always (in 16 out of 19 years) in the summer months of August, September, and October. Water Oualitv By removing clean mountain water before it enters the Colorado River, the Project would reduce the dilution effect provided by this clean mountain water. The Project's depletion would cause a proportionate decrease in dilution which in turn would cause a Qroportionate increase in heavy metal, ~ selenium, salts, PAHs, pesticides, an o er con aminant concentrations in the /~~ Colorado River. An increase in contaminant concentrations in the river would likely result in an increase in the bioaccumulation of these contaminants in the food chain which could adversely affect the endangered fishes, (~'` particularly the predatory Colorado squawfish. Selenium is of particular concern due to its effects on fish reproduction and its tendency to S _~''`~, concentrate in low velocity areas that are important habitats for Colorado ob+~ Gy squawfish and razorback suckers. .~ 'y Mass balance analyses were performed to determine the increase in selenium concentration caused by the Project at the year 2045 level of development. The increase was measured from existing conditions (current level of development, not section 7 baseline) within and below the 15-mile reach. Future selenium concentrations were predicted assuming a linear relationship between selenium concentration and flow and assuming the only change in flow in the future would be that caused by the Project. The selenium balance within the 15-mile reach showed a maximum increase from 2 to 2.088 ug/L, an increase less than the minimum detection limit. Below the 15-mile reach, the maximum increase is from 6 to 6.062 ug/L, also a very s a ~ T^~~..~,e. In most cases, the increases were considerably less than these maximums. While the analyses were limited to selenium, the Bureau believes that it is reasonable to infer that analyses of other water quality constituents would produce similar ranges of increase. The calculated increases in Selenium concentrations caused by the Project at the year 2045 level of development, although very small, represent increases when baseline levels are already near or above the threshold level of 2 ug/L recommended by the Service. Physical Habitat k~-Qvt- s""o~wy/-~ •~ s~~/~~wQs~ b~~ C~- /¢"' ~ f~ High spring flows are very important for creating and maintaining complex channel geomorphology and suitable spawning substrates, creating and providing ~ access to off-channel habitats, and possibly stimulating Colorado squawfish spawning migrations. Adequate summer and winter flows are important for providing a sufficient Quantity of preferred habitats for a duration and at a frequency necessary to support all life stages of viable populations of all endangered fishes. To the extent that the Project will reduce flows, the ability of the river to provide these functions will be reduced.