NGWA GENERAL DRILLING EXAM —OFFICIAL 2026–2027
PRACTICE STUDY GUIDE 200 original practice-question
stems • answers • instructional rationales • Certified
Well Driller (CWD) preparation
Section One — Questions 1–100
1. Which description best fits aquifer in groundwater drilling?
A) A chemical added to drilling fluid
B) A pump motor inside a well
C) A geologic unit that can yield usable groundwater
D) A layer that blocks all water movement
Correct Answer: C) A geologic unit that can yield usable groundwater
Rationale: An aquifer stores and transmits groundwater through interconnected pore spaces or
fractures. This distinction matters during planning, drilling, completion, testing, or maintenance
because an incorrect assumption can compromise performance or protection of groundwater.
The alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that
do not define the term. Apply the principle alongside the actual site conditions and applicable
local rules.
2. Which description best fits porosity in groundwater drilling?
A) The pressure delivered by a pump
B) The proportion of a material occupied by void spaces
C) The depth of the casing shoe
D) The rate of a drill bit rotation
Correct Answer: B) The proportion of a material occupied by void spaces
Rationale: Porosity describes the amount of void space available to store water. This distinction
matters during planning, drilling, completion, testing, or maintenance because an incorrect
assumption can compromise performance or protection of groundwater. The alternative
choices describe unrelated equipment, unsupported shortcuts, or concepts that do not define
the term. Apply the principle alongside the actual site conditions and applicable local rules.
3. Which description best fits permeability in groundwater drilling?
A) The mass of dry cuttings
B) The diameter of a water meter
C) The ability of material to transmit fluids through connected openings
D) The number of wells in a county
Correct Answer: C) The ability of material to transmit fluids through connected openings
,Rationale: Permeability describes how readily water moves through connected pathways. This
distinction matters during planning, drilling, completion, testing, or maintenance because an
incorrect assumption can compromise performance or protection of groundwater. The
alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that do
not define the term. Apply the principle alongside the actual site conditions and applicable local
rules.
4. Which description best fits hydraulic conductivity in groundwater drilling?
A) The total weight of a rig
B) A measurement of casing color
C) A measure of ease of water movement through a medium under a hydraulic gradient
D) A count of screen openings
Correct Answer: C) A measure of ease of water movement through a medium under a
hydraulic gradient
Rationale: Hydraulic conductivity combines properties of the medium and the fluid. This
distinction matters during planning, drilling, completion, testing, or maintenance because an
incorrect assumption can compromise performance or protection of groundwater. The
alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that do
not define the term. Apply the principle alongside the actual site conditions and applicable local
rules.
5. Which description best fits water table in groundwater drilling?
A) The top of the pump column
B) The upper surface of the saturated zone in an unconfined aquifer
C) The base of every well screen
D) The deepest bedrock surface
Correct Answer: B) The upper surface of the saturated zone in an unconfined aquifer
Rationale: The water table is the level where pore-water pressure is approximately atmospheric.
This distinction matters during planning, drilling, completion, testing, or maintenance because
an incorrect assumption can compromise performance or protection of groundwater. The
alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that do
not define the term. Apply the principle alongside the actual site conditions and applicable local
rules.
6. Which description best fits confined aquifer in groundwater drilling?
A) A shallow open ditch
B) A well with no casing
C) A water-bearing unit bounded by relatively low-permeability layers
D) A tank mounted on a rig
Correct Answer: C) A water-bearing unit bounded by relatively low-permeability layers
,Rationale: Confining layers restrict vertical flow and can create artesian pressure. This
distinction matters during planning, drilling, completion, testing, or maintenance because an
incorrect assumption can compromise performance or protection of groundwater. The
alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that do
not define the term. Apply the principle alongside the actual site conditions and applicable local
rules.
7. Which description best fits artesian condition in groundwater drilling?
A) Groundwater contains no minerals
B) All groundwater is hot
C) Every well flows above land surface
D) Groundwater rises in a well above the top of the confined aquifer
Correct Answer: D) Groundwater rises in a well above the top of the confined aquifer
Rationale: Artesian pressure may raise water above the aquifer top without necessarily reaching
the surface. This distinction matters during planning, drilling, completion, testing, or
maintenance because an incorrect assumption can compromise performance or protection of
groundwater. The alternative choices describe unrelated equipment, unsupported shortcuts, or
concepts that do not define the term. Apply the principle alongside the actual site conditions
and applicable local rules.
8. Which description best fits recharge in groundwater drilling?
A) A casing being threaded
B) Water entering the groundwater system
C) A pump shutting down
D) Water pumped into a storage tank
Correct Answer: B) Water entering the groundwater system
Rationale: Recharge replenishes groundwater from infiltration or other inflows. This distinction
matters during planning, drilling, completion, testing, or maintenance because an incorrect
assumption can compromise performance or protection of groundwater. The alternative
choices describe unrelated equipment, unsupported shortcuts, or concepts that do not define
the term. Apply the principle alongside the actual site conditions and applicable local rules.
9. Which description best fits discharge in groundwater drilling?
A) A mud pit being excavated
B) A driller changing gloves
C) A casing section being delivered
D) Groundwater leaving an aquifer through springs streams or pumping
Correct Answer: D) Groundwater leaving an aquifer through springs streams or pumping
Rationale: Discharge can occur naturally or through wells and other withdrawals. This
distinction matters during planning, drilling, completion, testing, or maintenance because an
, incorrect assumption can compromise performance or protection of groundwater. The
alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that do
not define the term. Apply the principle alongside the actual site conditions and applicable local
rules.
10. Which description best fits drawdown in groundwater drilling?
A) The diameter of the screen
B) The original total well depth
C) The distance between rig tires
D) The decline in water level caused by pumping relative to a reference level
Correct Answer: D) The decline in water level caused by pumping relative to a reference
level
Rationale: Drawdown measures water-level response to withdrawal and depends on well and
aquifer properties. This distinction matters during planning, drilling, completion, testing, or
maintenance because an incorrect assumption can compromise performance or protection of
groundwater. The alternative choices describe unrelated equipment, unsupported shortcuts, or
concepts that do not define the term. Apply the principle alongside the actual site conditions
and applicable local rules.
11. Which description best fits static water level in groundwater drilling?
A) The lowest level during pumping
B) The maximum pump pressure
C) Water level measured after adequate recovery without active pumping
D) The bottom of a borehole
Correct Answer: C) Water level measured after adequate recovery without active pumping
Rationale: Static water level is measured under nonpumping conditions after sufficient
stabilization. This distinction matters during planning, drilling, completion, testing, or
maintenance because an incorrect assumption can compromise performance or protection of
groundwater. The alternative choices describe unrelated equipment, unsupported shortcuts, or
concepts that do not define the term. Apply the principle alongside the actual site conditions
and applicable local rules.
12. Which description best fits pumping water level in groundwater drilling?
A) The casing wall thickness
B) The manufacturer's pump rating only
C) Water level observed while a well is being pumped
D) The original ground elevation
Correct Answer: C) Water level observed while a well is being pumped
Rationale: Pumping water level reflects drawdown during operation and depends on rate and
time. This distinction matters during planning, drilling, completion, testing, or maintenance
PRACTICE STUDY GUIDE 200 original practice-question
stems • answers • instructional rationales • Certified
Well Driller (CWD) preparation
Section One — Questions 1–100
1. Which description best fits aquifer in groundwater drilling?
A) A chemical added to drilling fluid
B) A pump motor inside a well
C) A geologic unit that can yield usable groundwater
D) A layer that blocks all water movement
Correct Answer: C) A geologic unit that can yield usable groundwater
Rationale: An aquifer stores and transmits groundwater through interconnected pore spaces or
fractures. This distinction matters during planning, drilling, completion, testing, or maintenance
because an incorrect assumption can compromise performance or protection of groundwater.
The alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that
do not define the term. Apply the principle alongside the actual site conditions and applicable
local rules.
2. Which description best fits porosity in groundwater drilling?
A) The pressure delivered by a pump
B) The proportion of a material occupied by void spaces
C) The depth of the casing shoe
D) The rate of a drill bit rotation
Correct Answer: B) The proportion of a material occupied by void spaces
Rationale: Porosity describes the amount of void space available to store water. This distinction
matters during planning, drilling, completion, testing, or maintenance because an incorrect
assumption can compromise performance or protection of groundwater. The alternative
choices describe unrelated equipment, unsupported shortcuts, or concepts that do not define
the term. Apply the principle alongside the actual site conditions and applicable local rules.
3. Which description best fits permeability in groundwater drilling?
A) The mass of dry cuttings
B) The diameter of a water meter
C) The ability of material to transmit fluids through connected openings
D) The number of wells in a county
Correct Answer: C) The ability of material to transmit fluids through connected openings
,Rationale: Permeability describes how readily water moves through connected pathways. This
distinction matters during planning, drilling, completion, testing, or maintenance because an
incorrect assumption can compromise performance or protection of groundwater. The
alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that do
not define the term. Apply the principle alongside the actual site conditions and applicable local
rules.
4. Which description best fits hydraulic conductivity in groundwater drilling?
A) The total weight of a rig
B) A measurement of casing color
C) A measure of ease of water movement through a medium under a hydraulic gradient
D) A count of screen openings
Correct Answer: C) A measure of ease of water movement through a medium under a
hydraulic gradient
Rationale: Hydraulic conductivity combines properties of the medium and the fluid. This
distinction matters during planning, drilling, completion, testing, or maintenance because an
incorrect assumption can compromise performance or protection of groundwater. The
alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that do
not define the term. Apply the principle alongside the actual site conditions and applicable local
rules.
5. Which description best fits water table in groundwater drilling?
A) The top of the pump column
B) The upper surface of the saturated zone in an unconfined aquifer
C) The base of every well screen
D) The deepest bedrock surface
Correct Answer: B) The upper surface of the saturated zone in an unconfined aquifer
Rationale: The water table is the level where pore-water pressure is approximately atmospheric.
This distinction matters during planning, drilling, completion, testing, or maintenance because
an incorrect assumption can compromise performance or protection of groundwater. The
alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that do
not define the term. Apply the principle alongside the actual site conditions and applicable local
rules.
6. Which description best fits confined aquifer in groundwater drilling?
A) A shallow open ditch
B) A well with no casing
C) A water-bearing unit bounded by relatively low-permeability layers
D) A tank mounted on a rig
Correct Answer: C) A water-bearing unit bounded by relatively low-permeability layers
,Rationale: Confining layers restrict vertical flow and can create artesian pressure. This
distinction matters during planning, drilling, completion, testing, or maintenance because an
incorrect assumption can compromise performance or protection of groundwater. The
alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that do
not define the term. Apply the principle alongside the actual site conditions and applicable local
rules.
7. Which description best fits artesian condition in groundwater drilling?
A) Groundwater contains no minerals
B) All groundwater is hot
C) Every well flows above land surface
D) Groundwater rises in a well above the top of the confined aquifer
Correct Answer: D) Groundwater rises in a well above the top of the confined aquifer
Rationale: Artesian pressure may raise water above the aquifer top without necessarily reaching
the surface. This distinction matters during planning, drilling, completion, testing, or
maintenance because an incorrect assumption can compromise performance or protection of
groundwater. The alternative choices describe unrelated equipment, unsupported shortcuts, or
concepts that do not define the term. Apply the principle alongside the actual site conditions
and applicable local rules.
8. Which description best fits recharge in groundwater drilling?
A) A casing being threaded
B) Water entering the groundwater system
C) A pump shutting down
D) Water pumped into a storage tank
Correct Answer: B) Water entering the groundwater system
Rationale: Recharge replenishes groundwater from infiltration or other inflows. This distinction
matters during planning, drilling, completion, testing, or maintenance because an incorrect
assumption can compromise performance or protection of groundwater. The alternative
choices describe unrelated equipment, unsupported shortcuts, or concepts that do not define
the term. Apply the principle alongside the actual site conditions and applicable local rules.
9. Which description best fits discharge in groundwater drilling?
A) A mud pit being excavated
B) A driller changing gloves
C) A casing section being delivered
D) Groundwater leaving an aquifer through springs streams or pumping
Correct Answer: D) Groundwater leaving an aquifer through springs streams or pumping
Rationale: Discharge can occur naturally or through wells and other withdrawals. This
distinction matters during planning, drilling, completion, testing, or maintenance because an
, incorrect assumption can compromise performance or protection of groundwater. The
alternative choices describe unrelated equipment, unsupported shortcuts, or concepts that do
not define the term. Apply the principle alongside the actual site conditions and applicable local
rules.
10. Which description best fits drawdown in groundwater drilling?
A) The diameter of the screen
B) The original total well depth
C) The distance between rig tires
D) The decline in water level caused by pumping relative to a reference level
Correct Answer: D) The decline in water level caused by pumping relative to a reference
level
Rationale: Drawdown measures water-level response to withdrawal and depends on well and
aquifer properties. This distinction matters during planning, drilling, completion, testing, or
maintenance because an incorrect assumption can compromise performance or protection of
groundwater. The alternative choices describe unrelated equipment, unsupported shortcuts, or
concepts that do not define the term. Apply the principle alongside the actual site conditions
and applicable local rules.
11. Which description best fits static water level in groundwater drilling?
A) The lowest level during pumping
B) The maximum pump pressure
C) Water level measured after adequate recovery without active pumping
D) The bottom of a borehole
Correct Answer: C) Water level measured after adequate recovery without active pumping
Rationale: Static water level is measured under nonpumping conditions after sufficient
stabilization. This distinction matters during planning, drilling, completion, testing, or
maintenance because an incorrect assumption can compromise performance or protection of
groundwater. The alternative choices describe unrelated equipment, unsupported shortcuts, or
concepts that do not define the term. Apply the principle alongside the actual site conditions
and applicable local rules.
12. Which description best fits pumping water level in groundwater drilling?
A) The casing wall thickness
B) The manufacturer's pump rating only
C) Water level observed while a well is being pumped
D) The original ground elevation
Correct Answer: C) Water level observed while a well is being pumped
Rationale: Pumping water level reflects drawdown during operation and depends on rate and
time. This distinction matters during planning, drilling, completion, testing, or maintenance
