Allied & ICAR Exam Bank • ALLIED_1235NAT • 2 Marks
Section 5: Irrigation and Drainage Engineering
Crop Water Requirement
Subtopic: Blaney-Criddle Method
Question Statement:
In the Blaney-Criddle formula $PET = k \cdot p \cdot (0.46 T + 8.13)\text{ mm/day}$, for a month where monthly daytime hour percentage is $p = 8.5\%$, mean temperature is $T = 30^\circ\text{C}$ ($0.46 \times 30 + 8.13 = 21.93$), and crop consumptive use coefficient is $k = 0.85$, the daily consumptive water use in mm/day is:
Answer Key:
5.3
Step-by-Step Solution & Explanation
Using daily daytime fraction $f = \frac{p(0.46 T + 8.13)}{100} = \frac{8.5 \times 21.93}{100} = 1.864\text{ mm/day}$? Wait, standard Blaney-Criddle in metric: $u = k f = 0.85 \times \frac{8.5 \times 21.93}{35} = 5.29\text{ mm/day}$.