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<br />-32- <br /> <br />Table 16. Mean & maximum daily water temperature (F) for the Dolores River at <br />river mile 6.6 and 12.2, for April-October 1990, 1991. <br /> <br /> River Mile 12.2 River Mile 6.6 <br /> Temperature Description 1990 1991 1990 1991 <br />Days of maximum temperature ~ 74 10 0 1 0 <br />Days of maximum temperature ~ 72 35 0 7 0 <br />Days of maximum t:emperature ~ 70 73 9 20 1 <br />Days of mean temperatures.~ 66 32 0 1 0 <br /> <br />This information provides two simple "ru1es-of-thumb" that could serve as an <br />"alert notice" to avoid severe damage to the stream aquatic resource. The <br />first is flows must be 50 cfs or higher to ensure the mean daily water <br />temperatures at Bradfield Bridge do not exceed the mean daily air temperature. <br />This becomes very critical to trout when the average water temperature exceeds <br />66 F. The second is a flow of 71 cfs or more is the minimum amount of water <br />necessary to keep the maximum daily water temperature at Bradfield Bridge in <br />the 70-72 F range when daily maximum air temperatures are in the 95-100 F <br />range. <br /> <br />CONCLUSIONS AND RECOMMENDATIONS <br /> <br />Conclusions <br /> <br />During 1991, a considerable amount of information was gathered about the <br />dynamic interactions between streamflow, air and water temperatures, and trout <br />population biology in the Dolores River tailrace fishery. Keys points <br />highlighted below provide information .for the short-term management of the <br />limited amount of water currently available for maintaining the stream fishery <br />resource, and to provide an assessment of the long-term water needs for <br />management of the Dolores River fishery downstream from McPhee Reservoir. <br /> <br />1. When maximum daytime air temperatures reach 95-1000 F, a 71 cfs <br />release is required to maintain maximum daily water temperatures in <br />the 70-720 F range. <br /> <br />2. At least 50 cfs is required to prevent the mean daily water <br />temperature (at Bradfield Bridge) from exceeding mean daily air <br />temperature. This becomes critical to trout when mean daily water <br />temperatures reach 660 F. <br /> <br />3. Fish trapping and tagging operations on the river in 1991 indicate <br />that large trout (~ 40 cm or ~ 16 in.) are unable to move upstream <br />more than a few hundred yards when the flows are 60 cfs or less. <br />Therefore, during the hottest portions of the summer (when air <br />temperatures reach or exceed 100 F) minimum releases should not drop <br />below 60 cfs. <br />