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changes in flow regimen may shift the balance from habitats favorable to <br />• rare endemic fishes to habitat conditions that may favor introduced fishes. <br />FWS believes that major causes for the decline of the Colorado squawfish, <br />humpback chub and bonytail chub include the effect of impoundments on and <br />water depletion from the Colorado River and its tributaries. .Using the best <br />scientific and commercial data presently available, the FWS has determined <br />that additional depletions of water may contribute to the extinction of <br />these fishes unless offset by active conservation measures to provide for <br />the continued existence of these species in their native habitats. Based on <br />current knowledge, FWS estimates that it is possible legally and physically <br />to deplete an additional 1.675 million acre-feet/year (Maf) in the Green and <br />Upper Colorado River sub-basins. FWS believes that for population levels of <br />listed fishes to be maintained with such additional depletions, it is <br />• essential to implement conservation measures. <br />Funding levels for conservation meastres to be funded by any particular <br />project are based upon the amount of projected average annual depletions <br />from the upper Colorado River system expected to result from the federal <br />action that is subject to the FWS consultation in proportion to the 1.675 <br />Maf available for development. It has been estimated by the Bureau of <br />Reclamation that a total of 1.906 Maf remains available for development in <br />the upper basin under the Colorado River Compact. Of this amount, ?31,000 <br />of are allocated to Arizona and New Mexico and will eventually be diverted <br />from the San Juan River and would not affect areas currently occupied by the <br />endangered fishes in the Colorado and Green River sub-basins. This leaves <br />1.675 Maf in a portion of the upper Colorado River basin as the value <br />• <br />8 <br />