Question

Given below are two statements
Statement I: Auger hole method is used to measure the hydraulic conductivity of soils above the water table
Statement II: Inverse auger hole method is used to measure the hydraulic conductivity of soils above the water table
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is correct but Statement II is false
• D. Statement I is incorrect but Statement II is true

Hint:

Auger hole method $\implies$ BELOW water table (water rises).
Inverse auger hole (Porchet) $\implies$ ABOVE water table (water infiltrates/falls).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Field measurement of saturated hydraulic conductivity ($K$) utilizes the auger hole method below a shallow water table and the inverse auger hole (Porchet) method in the unsaturated zone above the water table.
Key Formula or Approach:
\[ K = \frac{1.15 r \log_{10}(h_1 + r/2) - \log_{10}(h_2 + r/2)}{t_2 - t_1} \quad \text{(Inverse Auger Hole / Porchet Method)} \]

Step 2: Detailed Explanation:
1. Statement I: The classical Auger Hole Method (Ernst/Van Beers) is used exclusively below an existing shallow water table. Water is pumped out of the hole, and the rate of water rise is recorded. Hence, Statement I is incorrect.
2. Statement II: The Inverse Auger Hole Method (Porchet's Method) is used to measure hydraulic conductivity above the water table (in the unsaturated vadose zone). Water is poured into a dry auger hole, and the rate of infiltration/fall of water level is measured under constant/falling head. Hence, Statement II is true.

Step 3: Final Answer:
Thus, Statement I is incorrect but Statement II is true, matching option (D).