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23 <br />Hotchkiss National Hatchery near Lazear, Colorado. The third unit was <br />installed near the Highway 50 bridge that spans the Gunnison River at <br />Delta, Colorado. The first and third units, with only rare malfunctions, <br />were operated continually from November 1971 through December 14, 1977, <br />whereas the thermograph at the hatchery was only operated periodically. <br />The weekly charts (0-80oF range) were sent to me by the Bureau of Recla- <br />mation, which maintained and operated the thermographs. Maximum and mini- <br />mum daily temperatures were interpreted from the charts and recorded <br />for each month the units were operated. Some historical temperature <br />records for the Gunnison River near Grand Junction were obtained from the <br />Geological Survey records on file in the Bureau of Reclamation field <br />office at Grand Junction. <br />In addition to the above data, 45-day continuous recording Ryan <br />thermographs (28-800F) were operated rather sporadically by my field <br />crews at the following locations: below Blue Mesa and Morrow Point <br />reservoirs; in the Cimarron River about 1 mi above its confluence with the <br />Gunnison River; in the Gunnison River above the confluence of the North <br />Fork; in the North Fork just above its confluence with the Gunnison; <br />in the Uncompaghre River about 2 mi above Delta; and in the Gunnison <br />River at the Escalante bridge. Several factors contributed to the sporadic <br />operation of these stations: (a) some thermograph units were not procured <br />until the study was well underway; (b) some units malfunctioned, either <br />due to defects inherent to the clock or to tampering by fishermen who <br />happened to find the instruments in the streams; (c) five units were <br />actually lost during this study. Consequently, analyses of temperature <br />data presented in this paper will be principally from the two stations <br />having the longest historical records: below the Gunnison Tunnel, and <br />the Gunnison River at Grand Junction.