Question Bank • QB_SUB_IDE_0006 NAT • 2 Marks

Section 5: Irrigation and Drainage Engineering

Soil-Water-Plant Relationship

Subtopic: Measurement of infiltration, soil moisture and irrigation water infiltration

Question Statement:

Using Kostiakov's infiltration equation $F = 4.0 t^{0.6}$ (where cumulative depth $F$ is in cm and time $t$ is in hours), the infiltration rate $f = \frac{dF}{dt}$ at $t = 1.0\text{ hour}$ (in cm/h) is:

Answer Key:

2.4

Step-by-Step Solution & Explanation

Kostiakov equation: $F = a t^b = 4.0 t^{0.6}$ Infiltration rate: $f = \frac{dF}{dt} = a b t^{b-1} = 4.0 \times 0.6 \times (1.0)^{-0.4} = 2.40\text{ cm/h}$
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