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<br />diversity, and provide nutrient loading. Lower peaks provide and maintain spawning habitat. <br />The proposed operation should meet or exceed recommendations for spring flows. Table 3 <br />indicates how the frequency of spring flows are met under the proposed action and No Action <br />alternatives. Overall, the No Action alternative fails to meet the desired frequency and duration <br />ot the three categones ot spnng tlows (> I U,UUU cis, >/i,UUU cis, >:;,uOO cis) in the great majority <br />of years. Under the proposed action, the desired frequency and duration of the categories are met <br />or exceeded in all instances. Because of this, the spring flows under the proposed action should <br />meet many of the purposes of the flow recommendations, including generation of new cobble <br />sources, creation of channel diversity, provision of nutrient loading, maintenance of spawning <br />areas, and creation and maintenance of backwaters and other low-velocity habitats. <br /> <br />Maintaining low, stable base flows enhances nursery habitat conditions and flows between 500 <br />and 1,000 cfs optimize backwater conditions-selecting flows at the low end of the range <br />increases the availability of water for development and spring releases. Bliesner and Lamarra <br />(2000) reported that backwater habitats, which are extremely important for the endangered fish, <br />demonstrated a high degree of variability at low flows; but low flows clearly maximizcd this <br />habitat. <br /> <br />The proposed plan includes operations to attempt to maintain the base flows in the 500 to 1,000 <br />cfs range; however, this cannot always be accomplished. Inflows from tributaries, combined <br />with even minimum releases from Navajo Dam, will cause the 1,000 cfs to be exceeded at times. <br />This is particularly true during spring runoff when downstream tributaries are high and during <br />the frequent summer thunderstorms that can add sudden spike tlows to the river. In addition, <br />there are difficulties with travel time for increased flows to reach critical habitat and <br />discrepancies with gage readings in the critical habitat area. <br /> <br />Bliesner and Lamarra (2000) reports on studies that relate tlow levels to habitat creation and <br />maintenance and should be referred to for further information. <br /> <br />The proposed action will affect water quality in the San Juan River. Releases from Navajo <br />Reservoir of high quality water generally dilutes pollutants downstream. This dilution effect will <br />be increased during certain periods under the proposed plan but will be decreased in the winter <br />months and periodically at other times of the year as releascs are reduced. Contaminants of <br />concern include PARs and trace elements such as selenium, arsenic, copper, and zinc. Simpson <br />(1999) concluded "...that the concentrations of contaminants in biota inhabiting the mainstem of <br />the San Juan River were not consistently correlated with instream tlow discharges." <br /> <br />There is some belief that a more natural hydrograph may result in some natural control of <br />nonnative fish that compete with the endangered fish. This hypothesis was studied and initial <br />conclusions are that a negative response of nonnati ves to the more natural hydro graph during the <br />test flow period did not occur (Brooks, et aI, 2000). <br /> <br />18 <br /> <br />00688 <br />