NGWA PROFESSIONAL PRACTICE
EXAM PREP QUESTIONS AND
ANSWERS
1. Which principle states that the flow of groundwater through a porous medium is
proportional to the hydraulic gradient and the hydraulic conductivity?
A. Bernoulli’s Principle
B. Pascal’s Law
C. Darcy’s Law
D. Stokes’ Law
Answer: C
Conceptual Explanation: Darcy’s Law defines the relationship between flow rate,
hydraulic conductivity, and hydraulic gradient in porous media.
2. In well drilling, what is the primary function of a tremie pipe during the grouting process?
A. To circulate drilling mud to the surface
B. To stabilize the borehole walls during drilling
C. To measure the depth of the borehole
,D. To place grout from the bottom up to prevent bridging and voids
Answer: D
Conceptual Explanation: A tremie pipe ensures grout is placed at the bottom of the
annular space, displacing water and air to ensure a continuous seal.
3. Which type of aquifer is bounded above and below by impermeable layers or aquitards?
A. Unconfined aquifer
B. Confined aquifer
C. Perched aquifer
D. Artesian spring
Answer: B
Conceptual Explanation: A confined aquifer is sandwiched between low-permeability
layers, often leading to pressurized conditions.
4. What term describes the level to which water will rise in a well that penetrates a confined
aquifer?
A. Water table
B. Hydraulic head
C. Piezometric surface
D. Capillary fringe
, Answer: C
Conceptual Explanation: The piezometric (or potentiometric) surface represents the level
to which water rises under pressure in a confined aquifer.
5. Which drilling method uses a heavy bit attached to a wire rope that is repeatedly dropped
to crush rock?
A. Direct Rotary
B. Cable Tool
C. Reverse Rotary
D. Sonic Drilling
Answer: B
Conceptual Explanation: Cable tool drilling relies on the percussion of a heavy bit to
break up subsurface materials.
6. The ratio of the volume of voids to the total volume of a rock or soil is known as:
A. Specific Yield
B. Permeability
C. Transmissivity
D. Porosity
Answer: D
EXAM PREP QUESTIONS AND
ANSWERS
1. Which principle states that the flow of groundwater through a porous medium is
proportional to the hydraulic gradient and the hydraulic conductivity?
A. Bernoulli’s Principle
B. Pascal’s Law
C. Darcy’s Law
D. Stokes’ Law
Answer: C
Conceptual Explanation: Darcy’s Law defines the relationship between flow rate,
hydraulic conductivity, and hydraulic gradient in porous media.
2. In well drilling, what is the primary function of a tremie pipe during the grouting process?
A. To circulate drilling mud to the surface
B. To stabilize the borehole walls during drilling
C. To measure the depth of the borehole
,D. To place grout from the bottom up to prevent bridging and voids
Answer: D
Conceptual Explanation: A tremie pipe ensures grout is placed at the bottom of the
annular space, displacing water and air to ensure a continuous seal.
3. Which type of aquifer is bounded above and below by impermeable layers or aquitards?
A. Unconfined aquifer
B. Confined aquifer
C. Perched aquifer
D. Artesian spring
Answer: B
Conceptual Explanation: A confined aquifer is sandwiched between low-permeability
layers, often leading to pressurized conditions.
4. What term describes the level to which water will rise in a well that penetrates a confined
aquifer?
A. Water table
B. Hydraulic head
C. Piezometric surface
D. Capillary fringe
, Answer: C
Conceptual Explanation: The piezometric (or potentiometric) surface represents the level
to which water rises under pressure in a confined aquifer.
5. Which drilling method uses a heavy bit attached to a wire rope that is repeatedly dropped
to crush rock?
A. Direct Rotary
B. Cable Tool
C. Reverse Rotary
D. Sonic Drilling
Answer: B
Conceptual Explanation: Cable tool drilling relies on the percussion of a heavy bit to
break up subsurface materials.
6. The ratio of the volume of voids to the total volume of a rock or soil is known as:
A. Specific Yield
B. Permeability
C. Transmissivity
D. Porosity
Answer: D
