Question Bank • QB_IDE_EXP_091 NAT • 2 Marks

Section 5: Irrigation and Drainage Engineering

Soil-Water-Plant Relationship

Subtopic: Consumptive use and evapotranspiration

Question Statement:

In Blaney-Criddle formula $ET_0 = p (0.46 T + 8.13)$, for a month with mean daily temperature $T = 25^\circ\text{C}$ and mean daily percentage of annual daytime hours $p = 0.28$, calculate the reference evapotranspiration $ET_0$ in $\text{mm/day}$.

Answer Key:

5.5

Step-by-Step Solution & Explanation

$0.46 T + 8.13 = (0.46 \times 25) + 8.13 = 11.5 + 8.13 = 19.63$ $ET_0 = 0.28 \times 19.63 = 5.4964 \approx 5.50\text{ mm/day}$
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