Question

The infiltration rates observed by cylinder infiltrometers are affected by:
A. Cylinder diameter
B. Thickness of cylinder
C. Metal with which a cylinder is made of
D. Cylinder installation depth
Choose the correct answer from the options given below:

• A. A, B and D only
• B. A,B,C only
• C. A,B,C,D
• D. B,C and D only

Hint:

When evaluating infiltrometer errors, think about what might disrupt the ideal 1-D vertical flow. Lateral flow (affected by diameter), soil disturbance (affected by thickness and installation), and leakage (affected by installation depth) are the key issues.

Answer 1

The Correct Option is B

Step 1: Understand how a cylinder infiltrometer works.
A cylinder (or ring) is driven into the soil, water is ponded inside it, and the rate at which water level drops is measured. This gives a one-dimensional (vertical) infiltration rate. However, there are sources of error.
Step 2: Evaluate how each factor affects the measurement.
- A. Cylinder diameter: Water infiltrating from the cylinder can spread laterally outwards underground. This lateral spread is proportionally smaller for a larger diameter cylinder. Therefore, a smaller diameter ring will overestimate the true vertical infiltration rate more than a larger one. The diameter affects the result.
- B. Thickness of cylinder: A thick cylinder wall causes more soil disturbance when it is driven into the ground, which can alter the soil structure around the ring and affect the measured infiltration rate. Thickness matters.
- C. Metal with which a cylinder is made of: As long as the metal is inert and does not react with the water or soil (e.g., steel, aluminum), its composition will have no significant effect on the physical process of infiltration. This factor is not relevant.
- D. Cylinder installation depth: The cylinder must be driven deep enough to prevent leakage from under the sides and to contain the vertical flow. Insufficient depth can lead to errors. The depth of installation is important.
Step 3: Conclude the correct combination.
Factors A, B, and D all have a potential effect on the measured infiltration rate. Factor C does not.