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<br />J <br /> <br />~ <br />? <br /> <br />15 <br /> <br />eventually reenters the extreme southwest corner of Colorado near Four Corners. <br />Downstream of Four Corners, the San Juan River enters Utah and continues <br />northwesterly through the towns of Aneth, Montezuma Creek, Bluff, and Mexican <br />Hat, Utah, and empties into Lake Powell near Piute Farms Trading Post, <br /> <br />The San Juan River flows approximately 234 river miles from the Navajo Dam <br />downstream to Lake Powell. Of the 234 miles, about 177 are potentially <br />available to the Colorado squawfish. A diversion structure near Fruitland, New <br />Mexico (the Hogback at RH 177), and a weir at RH 183 span the entire river <br />channel and are believed to be effective blocks to upstream fish migrations <br />(Platania 1990). <br /> <br />The reach of currently known occupied habitat extends from Lake Powell upstream <br />to approximately RH 168 and will be significantly impacted due to upstream <br />water withdrawals associated with the Project. The mainstem San Juan River <br />above RH 168 to near Fruitland, New Mexico (RH 177), is available to Colorado <br />squawfish and may be occupied habitat now, or in the future, Observations of <br />700-800 mm squawfish at approximately RH 168 were made in June 1991 by <br />personnel from the New Mexico Department of Game and Fish (Propst 1991). The <br />Animas River, from which a majority of Project water will be diverted, is the <br />largest perennial tributary to the San Juan River and affects the entire length <br />of occupied Colorado squawfish habitat. Historically, flows in the San Juan <br />River prior to the Navajo Dam were highly variable. The change in flows at <br />three locations in the San Juan River are listed in Table 1. <br /> <br />~ <br /> <br />~ <br />,~ <br />~c <br /> <br />I~ <br /> <br /> Table 1 <br /> ,~ <br /> Change in Mean Monthly Flow After the Navajo Dam <br />Units. cfs Pre-Navajo Post-Navajo Percent Change <br /> Low Hiah Low Hiah Low Hiah <br />Farmington 170 13,471 418 9,803 +145% -27% <br />Shiprock 44 19,790 213 9,045 +384% -54% <br />Bluff 65 15,380 250 10,334 +284% -48% <br /> <br /> <br />Since 1963, the Navajo Dam has significantly altered the flow of the San Juan <br />River by storing spring peak flows and releasing water in summer, fall, and <br />winter months. The result is a 45 percent decrease in spring peak flows and <br />doubled winter base flows at the Bluff gage in Utah. Similar comparisons can be <br />made at the upstream gages at Shiprock and Farmington, New Mexico, <br />