NGWA (K) Water Systems Less Than 100
GPM exam with 100% correct Answers
1. What is the definition of a water well according to the National Ground Water
Association?
A) A borehole drilled for the purpose of mineral exploration
B) An excavation or structure created in the ground by digging, driving, boring, or
drilling to access groundwater
C) A pipe system designed for the disposal of sewage
D) A test pit dug to analyze soil mechanics for construction
Answer: B) An excavation or structure created in the ground by digging,
driving, boring, or drilling to access groundwater
Rationale: A water well is specifically defined as any man-made excavation or
structure created to access groundwater for use. Option A describes a mineral
exploration borehole, option C describes a septic system component, and option
D describes a soil test pit, none of which are intended for groundwater
extraction .
2. Which of the following best describes the term "aquifer"?
A) A layer of clay that prevents water movement
B) A saturated geological formation that yields water in sufficient quantities to a
well or spring
C) The uppermost surface of the zone of saturation
D) A rock formation that stores oil or natural gas
Answer: B) A saturated geological formation that yields water in sufficient
quantities to a well or spring
Rationale: An aquifer is defined by its ability to store and transmit water in
usable quantities. Option A describes an aquiclude or aquitard. Option C
describes the water table. Option D describes a reservoir for hydrocarbons, not
water .
,3. What is porosity?
A) The ability of a rock to transmit water
B) The measure of dissolved minerals in water
C) The percentage of void spaces in a rock or formation
D) The resistance of water to flow
Answer: C) The percentage of void spaces in a rock or formation
Rationale: Porosity is the measure of the empty spaces (pores) in a material,
expressed as a percentage of the total volume. Option A describes permeability.
Option B describes total dissolved solids. Option D describes viscosity .
4. How does permeability differ from porosity?
A) Permeability is the ability of a formation to transmit fluids, while porosity is the
measure of void spaces
B) Permeability is the measure of void spaces, while porosity is the ability to
transmit fluids
C) They are the same term and can be used interchangeably
D) Permeability measures water hardness, while porosity measures flow rate
Answer: A) Permeability is the ability of a formation to transmit fluids, while
porosity is the measure of void spaces
Rationale: A formation can have high porosity (many void spaces) but low
permeability if the pores are not interconnected. Permeability refers to the
connectivity of pores and the formation's ability to transmit water, which is a key
factor in well yield .
5. The standard unit used to measure permeability is the:
A) Pascal
B) Gallon per minute
C) Millidarcy (mD)
D) Parts per million
Answer: C) Millidarcy (mD)
Rationale: The darcy and millidarcy are the standard units for permeability,
, named after Henry Darcy who formulated the law of groundwater flow. PSI
measures pressure, GPM measures flow rate, and ppm measures concentration .
6. What is the water table?
A) The top of a confined aquifer where water is under pressure
B) The surface of an unconfined groundwater body at which the pressure is equal
to atmospheric pressure
C) The bottom of a well where water enters
D) A man-made structure for measuring evaporation rates
Answer: B) The surface of an unconfined groundwater body at which the
pressure is equal to atmospheric pressure
Rationale: The water table is the boundary between the unsaturated zone
(above) and the saturated zone (below) in an unconfined aquifer. In a confined
aquifer, the water level rises above the top of the aquifer due to pressure, which
is not the water table .
7. The static water level in a well is defined as:
A) The level of water in a well when it is being pumped at a constant rate
B) The distance from the ground surface to the bottom of the well
C) The level of water in a well when it is not being pumped and has reached
equilibrium
D) The depth at which the pump is installed
Answer: C) The level of water in a well when it is not being pumped and has
reached equilibrium
Rationale: Static water level represents the ambient water level in the well under
non-pumping conditions. The pumping water level (option A) is measured during
pumping. Total depth (option B) is a different measurement entirely .
8. When water is pumped from a well, the lowering of the water level is called:
A) Drawdown
B) Recovery
C) Specific capacity
D) Hydrostatic head
, Answer: A) Drawdown
Rationale: Drawdown is the difference between the static water level and the
pumping water level. Recovery is the process of water levels rising after pumping
stops. Specific capacity is the well yield divided by drawdown .
9. What is "specific capacity" of a well?
A) The total depth of the well in feet
B) The volume of water the well can produce over its lifetime
C) The discharge rate of the well per unit of drawdown, typically expressed as
GPM/ft
D) The hardness of the water produced by the well
Answer: C) The discharge rate of the well per unit of drawdown, typically
expressed as GPM/ft
Rationale: Specific capacity is a measure of well efficiency. It is calculated by
dividing the pumping rate (e.g., in gallons per minute) by the drawdown (in feet).
A decreasing specific capacity over time can indicate well deterioration .
10. Well yield is most commonly measured in:
A) PSI (pounds per square inch)
B) Feet per second
C) Gallons per minute (GPM) or cubic meters per day
D) Parts per million (ppm)
Answer: C) Gallons per minute (GPM) or cubic meters per day
Rationale: Well yield is a flow rate, quantifying the volume of water produced
over time. PSI is a pressure unit. PPM is a concentration unit. Feet per second is a
velocity unit .
11. What is the primary function of a well screen?
A) To seal the well from surface contamination
B) To allow water to enter the well from the aquifer while stabilizing the borehole
and excluding sediment
C) To increase the pressure of the water as it enters the pump
D) To filter out bacteria and viruses from the groundwater
GPM exam with 100% correct Answers
1. What is the definition of a water well according to the National Ground Water
Association?
A) A borehole drilled for the purpose of mineral exploration
B) An excavation or structure created in the ground by digging, driving, boring, or
drilling to access groundwater
C) A pipe system designed for the disposal of sewage
D) A test pit dug to analyze soil mechanics for construction
Answer: B) An excavation or structure created in the ground by digging,
driving, boring, or drilling to access groundwater
Rationale: A water well is specifically defined as any man-made excavation or
structure created to access groundwater for use. Option A describes a mineral
exploration borehole, option C describes a septic system component, and option
D describes a soil test pit, none of which are intended for groundwater
extraction .
2. Which of the following best describes the term "aquifer"?
A) A layer of clay that prevents water movement
B) A saturated geological formation that yields water in sufficient quantities to a
well or spring
C) The uppermost surface of the zone of saturation
D) A rock formation that stores oil or natural gas
Answer: B) A saturated geological formation that yields water in sufficient
quantities to a well or spring
Rationale: An aquifer is defined by its ability to store and transmit water in
usable quantities. Option A describes an aquiclude or aquitard. Option C
describes the water table. Option D describes a reservoir for hydrocarbons, not
water .
,3. What is porosity?
A) The ability of a rock to transmit water
B) The measure of dissolved minerals in water
C) The percentage of void spaces in a rock or formation
D) The resistance of water to flow
Answer: C) The percentage of void spaces in a rock or formation
Rationale: Porosity is the measure of the empty spaces (pores) in a material,
expressed as a percentage of the total volume. Option A describes permeability.
Option B describes total dissolved solids. Option D describes viscosity .
4. How does permeability differ from porosity?
A) Permeability is the ability of a formation to transmit fluids, while porosity is the
measure of void spaces
B) Permeability is the measure of void spaces, while porosity is the ability to
transmit fluids
C) They are the same term and can be used interchangeably
D) Permeability measures water hardness, while porosity measures flow rate
Answer: A) Permeability is the ability of a formation to transmit fluids, while
porosity is the measure of void spaces
Rationale: A formation can have high porosity (many void spaces) but low
permeability if the pores are not interconnected. Permeability refers to the
connectivity of pores and the formation's ability to transmit water, which is a key
factor in well yield .
5. The standard unit used to measure permeability is the:
A) Pascal
B) Gallon per minute
C) Millidarcy (mD)
D) Parts per million
Answer: C) Millidarcy (mD)
Rationale: The darcy and millidarcy are the standard units for permeability,
, named after Henry Darcy who formulated the law of groundwater flow. PSI
measures pressure, GPM measures flow rate, and ppm measures concentration .
6. What is the water table?
A) The top of a confined aquifer where water is under pressure
B) The surface of an unconfined groundwater body at which the pressure is equal
to atmospheric pressure
C) The bottom of a well where water enters
D) A man-made structure for measuring evaporation rates
Answer: B) The surface of an unconfined groundwater body at which the
pressure is equal to atmospheric pressure
Rationale: The water table is the boundary between the unsaturated zone
(above) and the saturated zone (below) in an unconfined aquifer. In a confined
aquifer, the water level rises above the top of the aquifer due to pressure, which
is not the water table .
7. The static water level in a well is defined as:
A) The level of water in a well when it is being pumped at a constant rate
B) The distance from the ground surface to the bottom of the well
C) The level of water in a well when it is not being pumped and has reached
equilibrium
D) The depth at which the pump is installed
Answer: C) The level of water in a well when it is not being pumped and has
reached equilibrium
Rationale: Static water level represents the ambient water level in the well under
non-pumping conditions. The pumping water level (option A) is measured during
pumping. Total depth (option B) is a different measurement entirely .
8. When water is pumped from a well, the lowering of the water level is called:
A) Drawdown
B) Recovery
C) Specific capacity
D) Hydrostatic head
, Answer: A) Drawdown
Rationale: Drawdown is the difference between the static water level and the
pumping water level. Recovery is the process of water levels rising after pumping
stops. Specific capacity is the well yield divided by drawdown .
9. What is "specific capacity" of a well?
A) The total depth of the well in feet
B) The volume of water the well can produce over its lifetime
C) The discharge rate of the well per unit of drawdown, typically expressed as
GPM/ft
D) The hardness of the water produced by the well
Answer: C) The discharge rate of the well per unit of drawdown, typically
expressed as GPM/ft
Rationale: Specific capacity is a measure of well efficiency. It is calculated by
dividing the pumping rate (e.g., in gallons per minute) by the drawdown (in feet).
A decreasing specific capacity over time can indicate well deterioration .
10. Well yield is most commonly measured in:
A) PSI (pounds per square inch)
B) Feet per second
C) Gallons per minute (GPM) or cubic meters per day
D) Parts per million (ppm)
Answer: C) Gallons per minute (GPM) or cubic meters per day
Rationale: Well yield is a flow rate, quantifying the volume of water produced
over time. PSI is a pressure unit. PPM is a concentration unit. Feet per second is a
velocity unit .
11. What is the primary function of a well screen?
A) To seal the well from surface contamination
B) To allow water to enter the well from the aquifer while stabilizing the borehole
and excluding sediment
C) To increase the pressure of the water as it enters the pump
D) To filter out bacteria and viruses from the groundwater
