Blaney Criddle Method
A simplified formula develops by Blaney and Criddle (1950) in which it correlates the consumptive use of water with the temperature and daytime hours.
By multiplying the mean monthly temperature t by the mean monthly percentage p of the maximum possible daytime hours of the year. A monthly consumptive use factor f is determined by this following equation
f = (pt./100)
The value of p depends on the period of the year and the latitude of the place.
The monthly consumptive use is given by this following formula:
Cu=k.P(1.8t + 32) /40
Cu = Monthly consumptive use in cm.
t = Mean monthly temperature in °C.
k = Crop factor, determined by experiments for each crop, under the environmental conditions of the particular area.
p = Monthly per cent of annual daylight hours that occur during the period.
If P(1.8t + 32) /40 is represented by f, now we get the equation is
The consumptive use of water for any given period is given by the sum of the monthly consumptive use values.
Thus, the formula was finally expressed as
where Cu is the seasonal consumptive use of water.