8167 - Laserfiche WebLink

Home Browse Search

much of July while mean water temperatures were ~ 49 F for nine days between the 9th and 26th of July, indicating the multi-stage outlet tubes had been in use throughout much of that month. This may indicate that darn releases ~ 100 cfs minimize the chances of water temperatures at Bradfield Bridge exceeding a daytime maximum of 70 F or a mean temperature of 66 F as long as maximum air temperatures do not exceed 95 F. Air temperature records at Bradfield Bridge indicate that 1993 summer temperatures (through August 4th) have been quite cool, with mean daily temperatures exceeding 70 F only twice and daytiII\e highs reaching 90 -94 F three times during this period. Use of the upper levels of the multi- stage outlet, coupled with discharges less than 100 cfs and air temperatures ~ 70 F (daily mean) or ~ 95 F (daytime maximum) will create stressful thermal conditions for the trout population. Table 15. Summary of the inflow to McPhee Reservoir and outflow to the Dolores River versus trout density and biomass responses, 1984- 1991. AFe/Water Year X 1000 Max. Outflow All Trout ~ 15cmd Water Year Inflow Outflow Winter> Vol. C (% Inflow Density Biomass 1984 580.3 408.7 ------ ---- 70.4 Increase Increase 1985 611.0 380.7 60.9 ---- 62.3 Increase Increase 1986 572.3 304.9 21. 3 ---- 53.3 Increase Increase 1987 589.2 398.8 80.8 99.3 67.7 Increase Increase 1988 259.2 104.6 28.3 99.6 40.4 Increase Increase 1989 263.1 115.3 28.5 100.3 43.8 Increase Increase 1990 142.5 37.7 24.9 81. 3 26.5 Decrease Decrease 1991 293.0 50.8 11.3 96.7 17.3 Decrease Decrease 1992 351. 9 172.3 11.7 100 49.0 Increase Increase 1993 598.2e 419.4e 30.9 100 70 :1 Increase Increase a Acre-feet b October 1 - March 31 C Percentage of maximum pool volume attained during that water yr. d Based on density and biomass estimates for total trout population ~ 15 cm in Tables 2, 3 and 9. e Projected estimates for entire 1993 water year. Table 16. Mean & maximum daily water temperature (F) for the Dolores River at river mile 6.6 and 12.2, for April 1990 - October 1992. Temperature Description River Mile 12.2 River Mile 6.6 1990 1991 1992 1990 1991 1992 Days of maximum temperature ~ 74 10 0 0 1 0 0 Days of maximum temperature > 72 35 0 0 7 0 0 Days of maximum temperature > 70 73 9 4 20 1 0 Days of mean temperatures ~ 66 32 0 1 1 0 0 -19-