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was also established in 1990 in Yellow Jacket Creek (YJ2) just above the confluence with <br />McElmo Creek and in Woods Canyon (WC) just downstream from irrigated land in the Yellow <br />Jacket area above the confluence with Sandstone Creek, a tributary of Yellow Jacket Creek <br />(Butler et al. 1995). Three samples were collected at YJ2 in March, July, and November 1990 <br />and were measured at less than 1 gg/L. However, the WC samples collected in April and <br />November were measured at 7 and 4 µg/L, respectively. The selenium concentrations in these <br />water samples and biota indicated that there may be a concern with selenium at ME3, ME4, and <br />WC. <br />In 1994, additional samples of water, bottom sediment, invertebrates, bird eggs, and fish eggs <br />were collected and analyzed for selenium loading at and near various sites including a pond on <br />Woods Creek (WCP) and a pond on upper Yellow Jacket Creek (YJP), which are adjacent to the <br />lands proposed to be irrigated (Butler et al. 1997). Additional sampling and analysis including <br />sediment, invertebrates, bird eggs, and fish eggs was done to follow a method for an aquatic <br />hazard assessment by Lemly (1995). Moderate to high ratings in the Lemly (1995) assessment <br />are considered categories of selenium levels at which wildlife can be impacted. When <br />combining selenium levels in water, sediment, invertebrates, and bird eggs (no fish eggs were <br />collected), the pond on Yellow Jacket Creek had a "low" overall hazard rating. The pond"on <br />Woods Creek had invertebrates containing 9.7 µg/g selenium dry weight and fish eggs were at <br />41.3 pg/g selenium dry weight causing the overall analysis to be considered in the "high" hazard <br />category. There were also water samples collected in April and July 1994 and analyzed for <br />selenium in a tributary of Sandstone Creek (SS). Sandstone Creek selenium levels were lpg/L <br />and below detection value of 1 pg/L, respectively. <br />Physical Habitat <br />The quantity and timing of flows influence how various habitats are formed and maintained. <br />Water depletions reduce the ability of the river to create and maintain backwaters, secondary <br />channels, and cobble bars; degradation of water quality lessens the ability of endangered species <br />to survive in these habitats. <br />Osmundson and Kaeding (1991) reported observations on the Colorado River (15-mile reach) <br />during the drought years of 1988-1990, that backwaters were filling in with silt and sand because <br />spring flows were not sufficient to flush out the fine sediment. Also, they reported that tamarisk <br />colonized sand and cobble bars, stabilizing the riverbanks. On the San Juan River, lack of <br />flooding since Navajo Dam was completed has caused establishment of exotic riparian <br />vegetation (primarily tamarisk and Russian olive) that has armored the channel banks resulting in <br />a narrowing of the channel with reduced flood capacity (Bliesner and Lamarra 1994). <br />As previously stated, Colorado pikeminnow spawn from late-June to late-August in <br />cobble/gravel areas typically found in riffle/run habitats. Following hatch, latval'Colorado <br />pikeminnow drift downstream to low velocity habitats. Important habitats during summer low <br />flow (August) are the San Juan's backwaters and secondary channels, used by larvae and young <br />Colorado pikeminnow. Razorback sucker spawning aggregations have been observed in the San <br />Juan River on the ascending limb of the hydrograph over cobble bars. <br />24