Question

Saturated hydraulic conductivity in situ is measured by

• A. Guelph permeameter
• B. Neutron probe
• C. Infiltrometer
• D. Piezometer

Hint:

The Guelph permeameter operates based on the Marriott bottle principle, maintaining a constant water level in an auger hole dug above the water table.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Saturated hydraulic conductivity ($K_{\text{sat}}$) measures the ease with which water flows through saturated soil pores.
Measuring $K_{\text{sat}}$ in situ (in the field) preserves the natural soil structure, macro-pores, and structural cracks.

Step 2: Detailed Explanation:
- Guelph Permeameter: An in situ constant-head well permeameter.
It measures the rate of water flow into an auger hole under a constant hydraulic head to calculate the field-saturated hydraulic conductivity ($K_{fs}$).
- Neutron Probe: Used to measure soil volumetric water content, not hydraulic conductivity.
- Infiltrometer (e.g., tension/double-ring): Measures infiltration rate, which differs from subsurface saturated hydraulic conductivity.
- Piezometer: Used to measure hydrostatic pressure or water table elevation.

Step 3: Final Answer:
The instrument used for in situ measurement of saturated hydraulic conductivity is the Guelph permeameter.