The series of mean monthly temperatures in °C are:
10.0, 11.1, 12.2, 14.4, 17.8, 20.0, 21.1, 22.2, 18.9, 17.8, 15.6, 12.8
The monthly potential evapotranspiration, using ONLINETHORNTHWAITE is:
2.324, 2.971, 3.757, 5.319, 8.067, 10.059, 10.873, 11.256, 7.975, 6.681, 4.950, 3.405.
The annual potential evapotranspiration is: 77.637 cm = 30.56 in = 2.547 ft
The annual evaporated volume is: 2.547 ft × 1,475 ac-ft × 43,560 ft2 /ac = 163,647,297 ft3
The mean annual runoff is: 50 ft3/s × 86,400 × 365 = 1,576,800,000 ft3
The annual loss to evaporation, in percentage of runoff, is: (163.6 = 1576.8 ) 100 = 10.37%
The Dendy and Bolton formula, for Q ≥ 2 in is:
S = 1965 e-0.055 Q (1.43 - 0.26 log A)
with S in ton/mi2/yr, A in mi2, and Q in inches.
S = 1965 e (-0.055 × 3.5) [ 1.43 - 0.26 log (188) ]
S = 1965 × 0.825 × ( 1.43 - 0.26 × 2.274 )
S = 1359.7 ton/mi2/yr.
S = 1359.7 × 188 = 255,624 ton/yr.