In the Blaney-Criddle method for estimating monthly consumptive use ($CU$), the monthly consumptive use factor $f$ in metric units is given by $f = \frac{p}{100}(1.8 T + 32)$ or $f = \frac{p \cdot T}{40}$, where $T$ is mean monthly temperature in $^\circ\text{C}$ and $p$ is:
Options:
(A) Monthly percentage of total daytime daylight hours of the year for the given latitude
(B) Mean atmospheric relative humidity percentage
(C) Soil porosity percentage
(D) Monthly precipitation percentage of annual total
Answer Key:
A
Step-by-Step Solution & Explanation
In the Blaney-Criddle formula ($U = k \cdot f$), the monthly daylight factor $p$ represents the monthly percentage of daytime hours of the year computed from astronomical latitude and solar declination tables. Option A is correct.