Which of the following surface geophysical exploration techniques are widely deployed in hydrogeological investigations to delineate freshwater aquifers and locate drilling sites?
Options:
(A) Direct-current electrical resistivity Vertical Electrical Sounding (VES) using Wenner or Schlumberger electrode arrays
(B) Seismic refraction profiling to map depth to impermeable bedrock and saturated unconfined water tables
(C) Electromagnetic (EM) profiling and Very Low Frequency (VLF) methods for locating water-bearing fault/fracture zones in hard rocks
(D) Differential Thermal Analysis (DTA) of cloud vapor
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
- Statements A, B, and C are standard surface geophysical groundwater exploration tools:
1. Electrical resistivity: Distinguishes freshwater sands (high-to-moderate resistivity) from saline water or impermeable clays (very low resistivity).
2. Seismic refraction: Acoustic velocity jumps across saturated strata and bedrock.
3. EM/VLF: Detects conductive water-filled fracture zones.
- Statement D is unrelated to subsurface geophysical exploration.