NGWA Water Systems Certification
Exam K (Under 100 GPM): Practice
Questions with Verified Answers &
Detailed Rationales – 2026 Edition
Section 1: Basic Principles & Definitions (Questions 1-20)
1. What does GPM stand for in water system design?
A) Gallons per meter
B) Gallons per minute
C) Gravity pressure measurement
D) Groundwater pump measure
Answer: B) Gallons per minute
Rationale: GPM (gallons per minute) is the standard unit used to measure
water flow rate in pump and water system design .
2. A water system producing less than 100 GPM is most commonly
classified as serving which type of customer?
A) Industrial manufacturing facility
B) Municipal water supply
, C) Residential or small commercial building
D) Agricultural irrigation system
Answer: C) Residential or small commercial building
Rationale: Systems under 100 GPM typically serve residential homes, small
commercial buildings, and small farms. Industrial and municipal systems
generally require higher capacities, often exceeding 100 GPM .
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
Answer: B) Viscosity
Rationale: Viscosity measures a fluid's resistance to flow. Higher viscosity
(e.g., cold water or fluids with additives) creates more resistance, requiring
more energy to pump, which directly influences 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
Answer: B) The ease with which water moves through a porous
medium, expressed in distance per time
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. Which term describes the volume of water that can be drained by
gravity from saturated material?
A) Specific storage
B) Specific yield
C) Porosity
D) Hydraulic gradient
Answer: B) Specific yield
Rationale: Specific yield is the portion of groundwater in a saturated
material that will drain under the influence of gravity. It represents the
drainable porosity of an aquifer .
6. A groundwater source that is confined between impermeable layers
is known as:
, A) Unconfined aquifer
B) Perched aquifer
C) Confined aquifer
D) Artesian spring
Answer: C) Confined aquifer
Rationale: A confined aquifer is trapped between impermeable rock or clay
layers, which prevents water from easily entering or leaving except through
wells .
7. The upper boundary of an unconfined aquifer is called the:
A) Confining layer
B) Water table
C) Potentiometric surface
D) Vadose zone
Answer: B) Water table
Rationale: The water table is the surface where groundwater pressure
equals atmospheric pressure, marking the top of the saturated zone in an
unconfined aquifer .
8. What is porosity?
A) The ability of water to flow through rock
B) The percentage of void spaces in a rock or unconsolidated material
Exam K (Under 100 GPM): Practice
Questions with Verified Answers &
Detailed Rationales – 2026 Edition
Section 1: Basic Principles & Definitions (Questions 1-20)
1. What does GPM stand for in water system design?
A) Gallons per meter
B) Gallons per minute
C) Gravity pressure measurement
D) Groundwater pump measure
Answer: B) Gallons per minute
Rationale: GPM (gallons per minute) is the standard unit used to measure
water flow rate in pump and water system design .
2. A water system producing less than 100 GPM is most commonly
classified as serving which type of customer?
A) Industrial manufacturing facility
B) Municipal water supply
, C) Residential or small commercial building
D) Agricultural irrigation system
Answer: C) Residential or small commercial building
Rationale: Systems under 100 GPM typically serve residential homes, small
commercial buildings, and small farms. Industrial and municipal systems
generally require higher capacities, often exceeding 100 GPM .
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
Answer: B) Viscosity
Rationale: Viscosity measures a fluid's resistance to flow. Higher viscosity
(e.g., cold water or fluids with additives) creates more resistance, requiring
more energy to pump, which directly influences 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
Answer: B) The ease with which water moves through a porous
medium, expressed in distance per time
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. Which term describes the volume of water that can be drained by
gravity from saturated material?
A) Specific storage
B) Specific yield
C) Porosity
D) Hydraulic gradient
Answer: B) Specific yield
Rationale: Specific yield is the portion of groundwater in a saturated
material that will drain under the influence of gravity. It represents the
drainable porosity of an aquifer .
6. A groundwater source that is confined between impermeable layers
is known as:
, A) Unconfined aquifer
B) Perched aquifer
C) Confined aquifer
D) Artesian spring
Answer: C) Confined aquifer
Rationale: A confined aquifer is trapped between impermeable rock or clay
layers, which prevents water from easily entering or leaving except through
wells .
7. The upper boundary of an unconfined aquifer is called the:
A) Confining layer
B) Water table
C) Potentiometric surface
D) Vadose zone
Answer: B) Water table
Rationale: The water table is the surface where groundwater pressure
equals atmospheric pressure, marking the top of the saturated zone in an
unconfined aquifer .
8. What is porosity?
A) The ability of water to flow through rock
B) The percentage of void spaces in a rock or unconsolidated material
