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<br />c.) <br />c...., <br />...... <br />{.O <br />.- <br />to <br /> <br />25 <br /> <br /> <br />120 <br />t15 <br />~ <br />II <br />~10 <br />2- <br />Il <br />~ 5 <br /> <br />o <br />10/01 <br /> <br />06/01 <br /> <br />08/01 <br /> <br />10/01 <br /> <br />01131 <br /> <br />04/01 <br />Data <br /> <br />12101 <br /> <br />!_AldIUIeta1950-61 _ArdlUleta1954-&1 <br /> <br />Figure 3.17. Seven-day running mean daily water temperature for the San <br />Juan River at Archuleta, New Mexico, during pre-dam and post- <br />dam flow periods (Source: Bliesner and Lamarra 2000). <br /> <br />and roundtail chub reproduced in the mainstem above the mouth of the Yampa River; but Colorado <br />pikeminnowand razorback sucker used the area more sporadically (Holden and Crist 198 I, Bestgen and <br />Crist 2000). The Animas River provides a more-natural temperature regime, warming the colder San Juan <br />River water during the spring and sununer, similar to the Yampa River. The change in temperature caused <br />by Navajo Dam effectively reduced the potential range of the endangered fish species by another 45 miles, <br />from mouth of the Animas River (RM 180.0) to Navajo Dam (RM 225.0), although other native species <br />still utilize most of this reach. <br /> <br />Bliesner and Lamarra (2000) also noted that sununer water temperatures declined between the mouth of <br />the Animas River and Shiprock, New Mexico. Figure 3.18 shows actual and modeled temperatures at <br />Shiprock from pre- (195 I - I 96 I) and post-dam (1964-1968) periods and the 7 -year research period <br />(1993 -1998). Colorado pikeminnow spawn at temperatures of about 20 0 C (Vanicek and Kramer 1969, <br />Hamman 198 I, Tyus 1990). Temperatures at Shiprock, New Mexico, reached 20 oC in mid to late June <br />during the pre-dam period. The colder post-dam releases delayed the time of reaching this temperature <br />by about 2 weeks, and during the 7-year research period it was 3 weeks later (early to mid-July). It should <br />be noted that the study period was a relatively high water period that resulted in above-normal flows both <br />from Navajo Dam and the Animas River (Bliesner and Lamarra 2000). These higher flows likely <br />contributed to a lower sununer water temperature. The pre-dam period for which temperature data were <br />available (1951-1961) was a relatively low-flow period. Average high flows during 1993 to 1998 were <br />about 9,100 cfs, and during 1951 to 1961 they were 7,200 cfs. This suggests that the temperature <br />difference during the 7-year research period may not reflect the long-term difference. <br /> <br />September 2000 <br /> <br />3-40 <br /> <br />Program Evaluation Report <br />