Modified Blaney-Criddle for Excel

temperature, the value of which is expressed as
kt = 0.0173t - 0.314
kc = a coefficient reflecting the growth stage of the crop (Table B-I-1)
Calculation of Monthly Supplemental Crop Requirement and Allocation
The calculations to determine crop evapotraspiration are based on selected crop growth coefficients (Table B-I-1),
rainfall, temperature and solar radiation for selected rainfall stations (Figures B-I-1 through B-I-15 and Table B-I-2)
and net depth of application (Figures B-I-1 through B-I-15). In order to estimate monthly evapotranspiration, the
District approximates equations (1) and (2) as follows:
(3) f (m) = ( t (m) x p (m) ) / 100
(4) kt (m) = (0.0173 x t (m)) - 0.314
(5) kt f (m) = f (m) x kt (m)
(6) U (m) = kt f (m) x kc (m)
where:
m = month of year
f (m) = monthly evapotranspiration factor,
t (m) = average monthly temperature (Table B-I-2),
p (m) = monthly percentage of annual daylight hours (Table B-I-2),
kt (m) = kt,
U (m) = monthly evapotranspiration, and
kc (m) = monthly crop growth coefficient (Table B-I-1).
The effective rainfall available for crop evapotranspiration is calculated as a function of the 1-in-10-year drought
rainfall as:
(7) Rt1 (m) = ( 0.70917 x (Rt (m) 0.82416 ) - 0.11556)
(8) Ul (m) = 10 (0.02426 x U(m))
(9) F1 = 0.531747 + ( 0.295154 x D ) – ( 0 .057697 x D 2 ) + ( 0.003804 x D 3 )
(10) Re (m) = Rt1 (m) x Ul (m) x F1
where:
Rt1 (m) = monthly effective rainfall factor considering 1-in-10 monthly rainfall,
Rt (m) = 1-in-10 monthly rainfall (Table B-I-2),
Ul (m) = monthly effective rainfall factor considering monthly evapotranspiration,
F1 = soil factor,
D = net depth of,application (see Figures B-I-1 through B-I-15), and