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<br />• 4.3 Evapotransciration <br />An analysis of the evaporation pan data showed a typi- <br />cal daytime evaporation rate of 3/16" in ten hours, or 0.00156 <br />feet/hour. The maximum recorded rate was about 3/16" in 5.3 <br />hours on 29 August or 0.00293 feet/hour. Pan data are presented <br />in Appendix B. <br />To calculate evaporative losses, an estimate of the <br />surface area of the reach of interest was needed. The average <br />stream width for the entire 4,6 mile reach was estimated at 150 <br />feet. Thus, 4.6 miles (5280 ft/mi) (150 ft) = 3.6432 x 106 ft2 <br />is the estimated surface area. Evaporative losses were calcu- <br />lated as follows: <br />Averaee losses: <br />• (3.6432 x 106 ft2)(0.00156 ft/hr)/(3600 sec/!:r) _ <br />1.58 cfs <br />• Maximum losses: <br />(3.6432 x 106 ft-)(0.00293 ft/hr)/(3600 sec/hr) _ <br />2.97 cfs <br />Losses from uptake and transpiration by riparian vege- <br />tation were assumed to be occurring at 60 percent of the rate <br />of direct water surface evaporation. It was estimated that <br />significant riparian vegetation occurred along 60 percent of <br />the 4.6 mile reach and averaged 80 feet in width. Therefore, <br />losses due to vegetation were estimated to be: <br />[0.00156 ft/hr (0.60)(4.6 mi)(0.60)(80 ft) <br />(5280 ft/mi)J/(3600 sec/hr) = 0.30 cfs <br />n <br />lJ <br />4-11 <br />