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{ ~ c 24 Water depletions reduce the .ability of the river to create and maintain these important habitats and reduce the frequency and duration of availability of these habitats. Food supply, predation, and competition are important elements of the biological environment. Food supply is a function of nutrient supply and productivity, which could be limited by reduction of high spring flows brought about by water depletions. Predation and competition from nonnative fish species have been identified as factors in the decline of the endangered fishes. Water depletions contribute to alterations in flow regimes that favor nonnative fishes. The Service concludes that water depletions impact the primary constituent elements. Water Quantity The Project will affect flows within critical habitat in the mainstem Colorado River from the Plateau Creek confluence downstream to Lake Powell. In discussing impacts to flows resulting from this project, it is helpful to break up this entire affected reach into four subreaches. The "Cameo reach" extends from the Plateau Creek confluence to a point just below the major diversions at Palisade. The "15-mile reach" extends from the downstream end of the Cameo reach to the Gunnison River confluence. The "u er 18-mil ;-~:s reach" extends from the Gunnison River confluence to Persigo Was The ~,M..+~~ "Persigo-Lake Powell" reach extends from Persigo Wash to Lake Powell. ~ ~-. Because Plateau Creek is not designated critical habitat and is not considered occupied habitat, reduced flows in Plateau Creek would not directly affect ~ endangered fishes. However, because Plateau Creek is a tributary to the Colorado River, reduction of flows in Plateau Creek would cause a reduction of flows within critical habitat in the mainstem Colorado River beginning at the Plateau Creek confluence approximately seven miles upstream of Palisade. --~. Almost all of the return flows reenter the Colorado River as effluent from the Persi o Waste W Gated o a roximately seven miles downstream of the Gunnison River~onfleence. Because o he diversion an t e re urn o wa er occur within designated critical habitat for the endangered fishes, depletion effects must be measured in terms of the flow reduction between the point of diversion and the return flow and in terms of the overall depletion to the basin. . ~ Flow red ctions to the 15-mile reach, and u - ach are fir" e u~v to Ute Wat ess re acement reservoir rel a The ~~p~` f ow reduction to the Persigo-Lake Powel teat is equiva ent to Ute Water's ~~„~. diversion less replacement reservoir releases and return flows; the flow ~,~ reduction to the Persigo-Lake Powell reach represents the overall depletion to the basin. Construction of a larger pipeline will result in the continued historic depletion of water as well as a new depletion associated with the increased diversion of water to meet demands beyond historic levels. The historic depletion of water is defined as the average annual depletion which occurred prior to January 1988, the date the Recovery Implementation Program for Endangered Fish Species in the Upper Colorado River Basin was initiated. Because the Project's historic depletion has generally increased over time as Ute Water's service area has increased, the historic depletion was calculated