NGWA Water Systems Certification Exam
(Greater Than 100 GPM – Exam L)
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
SECTION 1: HYDRAULIC PRINCIPLES & HYDROGEOLOG
1. What is the primary difference between a confined and an unconfined
aquifer?
A) A confined aquifer is bounded above and below by impermeable layers,
whereas an unconfined aquifer is only bounded below by an impermeable layer.
B) A confined aquifer has a water table, while an unconfined aquifer does not.
C) An unconfined aquifer is always deeper than a confined aquifer.
D) Confined aquifers are only found in coastal regions.
Correct ,,,,answer,,,,: A
Rationale: A confined aquifer is trapped between impermeable layers (aquitards),
which pressurizes the water. An unconfined aquifer is open to the surface and
recharged directly by precipitation; its upper boundary is the water table.
2. Which of the following best describes porosity in hydrogeology?
,A) The ability of a rock or soil to transmit water.
B) The percentage of void space within a rock or soil that can hold water.
C) The rate at which water moves through a material.
D) The pressure exerted by water in an aquifer.
Correct ,,,,answer,,,,: B
Rationale: Porosity refers to the proportion of void spaces within a material,
indicating how much water it can potentially hold. Permeability is the ability to
transmit water.
3. What property of water describes its resistance to flow and deformation,
directly affecting pump selection?
A) Density
B) Viscosity
C) Conductivity
D) Surface tension
Correct ,,,,answer,,,,: B
Rationale: Viscosity measures water's resistance to flow. Higher viscosity creates
more resistance, requiring more energy to pump and directly influencing pump
selection and system design.
4. What is hydraulic conductivity?
,A) The amount of water stored in an aquifer
B) The ease with which water moves through a porous medium, expressed in
distance per time
C) The total head loss in a pumping system
D) The maximum yield of a well
Correct ,,,,answer,,,,: B
Rationale: Hydraulic conductivity measures the ease with which water moves
through a porous medium and is commonly expressed in units of distance per time
(e.g., meters per day or feet per day).
5. The term "specific yield" refers to:
A) Water that evaporates from soil
B) Water lost to leakage
C) The volume of water that can be drained by gravity from saturated material
D) Total water in an aquifer
Correct ,,,,answer,,,,: C
Rationale: Specific yield is the portion of groundwater in a saturated material that
will drain under the influence of gravity, expressed as a percentage of the total
volume. It represents the water that can actually be extracted from an aquifer.
6. In a hydrogeologic context, the term "drawdown" refers to:
, A) The distance from the land surface to the bottom of the aquifer
B) The decrease in water level in a well during pumping
C) The rate at which water is replenished in an aquifer
D) The total volume of water in the aquifer
Correct ,,,,answer,,,,: B
Rationale: Drawdown is the lowering of the water level in a well due to pumping,
representing the difference between the static (non-pumping) water level and the
pumping water level.
7. Which method is commonly used to determine aquifer transmissivity?
A) Pumping test (aquifer test)
B) Slug test
C) Soil texture analysis
D) Electrical resistivity
Correct ,,,,answer,,,,: A
Rationale: Pumping tests (aquifer tests) are the primary method for determining
transmissivity and storage coefficient. Slug tests are also used but are more
localized. Transmissivity is the rate at which water is transmitted through a unit
width of an aquifer under a unit hydraulic gradient.
8. An aquitard is best described as:
(Greater Than 100 GPM – Exam L)
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
SECTION 1: HYDRAULIC PRINCIPLES & HYDROGEOLOG
1. What is the primary difference between a confined and an unconfined
aquifer?
A) A confined aquifer is bounded above and below by impermeable layers,
whereas an unconfined aquifer is only bounded below by an impermeable layer.
B) A confined aquifer has a water table, while an unconfined aquifer does not.
C) An unconfined aquifer is always deeper than a confined aquifer.
D) Confined aquifers are only found in coastal regions.
Correct ,,,,answer,,,,: A
Rationale: A confined aquifer is trapped between impermeable layers (aquitards),
which pressurizes the water. An unconfined aquifer is open to the surface and
recharged directly by precipitation; its upper boundary is the water table.
2. Which of the following best describes porosity in hydrogeology?
,A) The ability of a rock or soil to transmit water.
B) The percentage of void space within a rock or soil that can hold water.
C) The rate at which water moves through a material.
D) The pressure exerted by water in an aquifer.
Correct ,,,,answer,,,,: B
Rationale: Porosity refers to the proportion of void spaces within a material,
indicating how much water it can potentially hold. Permeability is the ability to
transmit water.
3. What property of water describes its resistance to flow and deformation,
directly affecting pump selection?
A) Density
B) Viscosity
C) Conductivity
D) Surface tension
Correct ,,,,answer,,,,: B
Rationale: Viscosity measures water's resistance to flow. Higher viscosity creates
more resistance, requiring more energy to pump and directly influencing pump
selection and system design.
4. What is hydraulic conductivity?
,A) The amount of water stored in an aquifer
B) The ease with which water moves through a porous medium, expressed in
distance per time
C) The total head loss in a pumping system
D) The maximum yield of a well
Correct ,,,,answer,,,,: B
Rationale: Hydraulic conductivity measures the ease with which water moves
through a porous medium and is commonly expressed in units of distance per time
(e.g., meters per day or feet per day).
5. The term "specific yield" refers to:
A) Water that evaporates from soil
B) Water lost to leakage
C) The volume of water that can be drained by gravity from saturated material
D) Total water in an aquifer
Correct ,,,,answer,,,,: C
Rationale: Specific yield is the portion of groundwater in a saturated material that
will drain under the influence of gravity, expressed as a percentage of the total
volume. It represents the water that can actually be extracted from an aquifer.
6. In a hydrogeologic context, the term "drawdown" refers to:
, A) The distance from the land surface to the bottom of the aquifer
B) The decrease in water level in a well during pumping
C) The rate at which water is replenished in an aquifer
D) The total volume of water in the aquifer
Correct ,,,,answer,,,,: B
Rationale: Drawdown is the lowering of the water level in a well due to pumping,
representing the difference between the static (non-pumping) water level and the
pumping water level.
7. Which method is commonly used to determine aquifer transmissivity?
A) Pumping test (aquifer test)
B) Slug test
C) Soil texture analysis
D) Electrical resistivity
Correct ,,,,answer,,,,: A
Rationale: Pumping tests (aquifer tests) are the primary method for determining
transmissivity and storage coefficient. Slug tests are also used but are more
localized. Transmissivity is the rate at which water is transmitted through a unit
width of an aquifer under a unit hydraulic gradient.
8. An aquitard is best described as:
