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<br />. <br /> <br />. <br /> <br />Area Manager <br />DRAFT <br /> <br />38 <br /> <br />high and low flows will be discussed in more detail. Changes in channel morphology will be <br />discussed in relation to changes in flow. <br /> <br />VVatertenaperature <br /> <br />The cold water below Navajo Dam limits the distribution of the endangered fish in the San Juan <br />River. Water released from Navajo Dam is a constant 40C (390F), creating conditions that are <br />not suitable for either pikeminnow or razorback sucker for approximately 70 km (45 mi) <br />downstream (confluence with the Animas River). Although spawning could have occurred at <br />Archuleta (approximately 14 km [9 mil below the dam) before Navajo Dam was constructed, <br />post-dam temperatures are too cold for successful pikeminnow spawning (Holden 1999). The <br />threshold temperatures for spawning at Shiprock (approximately 125 km [78 mil below the dam) <br />occur about 2 weeks later on average than pre-dam (Holden 1999). There is speculation that the <br />large volume of cold water in the upper Green River may be a major reason why larVal <br />pikeminnow drift so far downstream (Holden 2000). Because the combination of a suitable <br />spawning bar and suitable temperatures occur so far downstream on the San Juan, there is a <br />greater chance that larval fish will drift into Lake Powell and be lost from the population. <br />Dudley and Platania (2000) found that drifting laraval pikeminnow would be transported from <br />the spawning bar in the San Juan River to Lake Powell in about three days. For those larval fish <br />not carried into Lake Powell, a delay in spawning (which reduces the amount oftime YOY have <br />to grow before winter) and overall colder water temperatures (resulting in slower growth), could <br />lead to smaller, less fit YOY, and reduce survival. While this reasoning is biologically sound, <br />the consequences oflower water temperatures on survival and recruitment ofpikeminnow have <br />not been tested on the San Juan River. <br /> <br />Blockage of fish passage <br /> <br />Like other major dams on the Colorado River and its tributaries, Navajo Dam blocked all fish <br />passage. Razorback sucker and pikeminnow that may have been trapped above the reservoir <br />have all died or were killed during treatment with rotenone (Olson 1962, Holden 1999). Glen <br />Canyon Dam, completed in 1963, isolated the San Juan populations of razorback sucker and <br />pikeminnow from the lower Colorado River populations. In addition to the major dams, <br />diversion structures constructed in the San Juan River have also created barriers to fish passage. <br /> <br />Ryden and Pfeifer (1993) identified five diversion structures between Farmington, New Mexico, <br />and the Utah state line that potentially acted as barriers to fish passage at certain flows (Cudei, <br />Hogback, Four Corners Power Plant, San Juan Generating Station, and Fruitland Irrigation Canal. <br />diversions). Since radio telemetry studies were initiated on the San Juan River in 1991, only one <br />radio-tagged pikerninnow was recorded moving upstream past one of the diversions. In 1995, an <br />adult pikeminnow moved above the Cudei Diversion and then returned back downstream (Miller <br />] 995). Other native fish had been found to move either upstream or downstream over all five of <br />the weirs (Buntjer and Brooks 1997, Ryden 2000a). In 2001, Cudei Diversion (RM 142) was <br />removed from the river and Hogback Diversion (previously an earth and gravel berm structure), <br />which had to be rebuilt every year, was made into a permanent structure with a non-selective fish <br />ladder. Channel catfish that were tagged downstream of the Hogback Diversion in spring and <br /> <br />00lHl <br />