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COitOOQ~TIOM <br />' ~ 4.3 Evapotranspiration <br />q 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 Baas about 3/16" in 5.3 <br />_; <br />hours on 29 August or 0.00293 feet/hour. Pan data are presented <br />' in Appendix B. <br />i <br />To calculate evaporative losses, an estimate of the <br />surface area of the reach of interest was needed. The average <br />stream caidth 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 ftZ <br />is the estimated surface area. Evaporative losses were calcu- <br />lated as follows: <br />• Average Losses: <br />J •~~ (3.6432 x 106 ft2)(0.00156 ft/hr)/(3600 sec/hr) _ <br />9 1.58 cfs <br />• Maximum losses: <br />i <br />(3.6432 x 106 ft2)(0.00293 ft/hr)/(3600 sec/hr) _ <br />2.97 cfs <br />Losses from uptake and transpiration by riparian vege- <br />~ tation were assumed co be occurring at b0 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)(0.6C)(80 ft) <br />~ (5280 ft/mi)]/(3600 sec/hr) = 0.30 cfs <br />y • <br />f <br />] 4-11 <br />