NGWA Master Groundwater Contractor
Certification Exam (MGWC) Practice
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of a grout seal in a water well?
A. To improve water flow
B. To prevent contamination of the aquifer
C. To increase the well depth
D. To enhance pump efficiency
B. To prevent contamination of the aquifer
Rationale: A grout seal prevents surface water and contaminants
from entering the well, protecting groundwater quality.
2. Which drilling method is most commonly used for deep water wells?
A. Cable tool
, B. Air rotary
C. Mud rotary
D. Auger
C. Mud rotary
Rationale: Mud rotary drilling allows for deep penetration through
various formations and maintains borehole stability.
3. The safe yield of an aquifer is defined as:
A. The maximum water extracted without depleting the aquifer
B. The total storage capacity of the aquifer
C. The flow from a spring
D. The recharge rate of the soil only
A. The maximum water extracted without depleting the aquifer
Rationale: Safe yield ensures sustainable use by balancing extraction
and natural recharge.
4. Which type of well casing is most resistant to corrosion?
A. PVC
B. Galvanized steel
C. Wood
D. Aluminum
A. PVC
Rationale: PVC is chemically inert, resistant to corrosion, and widely
used in modern well construction.
,5. In well development, the primary goal is to:
A. Increase water storage
B. Remove drilling fluids and fine sediments
C. Seal off non-productive zones
D. Install the pump
B. Remove drilling fluids and fine sediments
Rationale: Well development improves yield and water quality by
clearing fine particles and drilling mud from the formation.
6. What is the typical depth limit for hand-dug wells?
A. 10–20 feet
B. 30–50 feet
C. 50–100 feet
D. 100–150 feet
B. 30–50 feet
Rationale: Hand-dug wells are shallow due to limitations in
excavation methods and safety.
7. Which factor primarily influences aquifer transmissivity?
A. Well diameter
B. Hydraulic conductivity and aquifer thickness
C. Pump type
D. Well depth
B. Hydraulic conductivity and aquifer thickness
, Rationale: Transmissivity depends on how easily water moves
through the aquifer and the thickness of the aquifer layer.
8. What is the recommended minimum distance between a septic
system and a well?
A. 10 feet
B. 25 feet
C. 50 feet
D. 100 feet
D. 100 feet
Rationale: Adequate separation reduces the risk of contamination
from wastewater.
9. Which device is used to measure well yield during pumping tests?
A. Anemometer
B. Flow meter
C. Seismograph
D. Hygrometer
B. Flow meter
Rationale: Flow meters provide accurate measurements of water
discharge from a well.
10. Artesian wells occur when:
A. Water flows uphill naturally due to pressure
B. The aquifer is unconfined
C. Water table is below the pump
Certification Exam (MGWC) Practice
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of a grout seal in a water well?
A. To improve water flow
B. To prevent contamination of the aquifer
C. To increase the well depth
D. To enhance pump efficiency
B. To prevent contamination of the aquifer
Rationale: A grout seal prevents surface water and contaminants
from entering the well, protecting groundwater quality.
2. Which drilling method is most commonly used for deep water wells?
A. Cable tool
, B. Air rotary
C. Mud rotary
D. Auger
C. Mud rotary
Rationale: Mud rotary drilling allows for deep penetration through
various formations and maintains borehole stability.
3. The safe yield of an aquifer is defined as:
A. The maximum water extracted without depleting the aquifer
B. The total storage capacity of the aquifer
C. The flow from a spring
D. The recharge rate of the soil only
A. The maximum water extracted without depleting the aquifer
Rationale: Safe yield ensures sustainable use by balancing extraction
and natural recharge.
4. Which type of well casing is most resistant to corrosion?
A. PVC
B. Galvanized steel
C. Wood
D. Aluminum
A. PVC
Rationale: PVC is chemically inert, resistant to corrosion, and widely
used in modern well construction.
,5. In well development, the primary goal is to:
A. Increase water storage
B. Remove drilling fluids and fine sediments
C. Seal off non-productive zones
D. Install the pump
B. Remove drilling fluids and fine sediments
Rationale: Well development improves yield and water quality by
clearing fine particles and drilling mud from the formation.
6. What is the typical depth limit for hand-dug wells?
A. 10–20 feet
B. 30–50 feet
C. 50–100 feet
D. 100–150 feet
B. 30–50 feet
Rationale: Hand-dug wells are shallow due to limitations in
excavation methods and safety.
7. Which factor primarily influences aquifer transmissivity?
A. Well diameter
B. Hydraulic conductivity and aquifer thickness
C. Pump type
D. Well depth
B. Hydraulic conductivity and aquifer thickness
, Rationale: Transmissivity depends on how easily water moves
through the aquifer and the thickness of the aquifer layer.
8. What is the recommended minimum distance between a septic
system and a well?
A. 10 feet
B. 25 feet
C. 50 feet
D. 100 feet
D. 100 feet
Rationale: Adequate separation reduces the risk of contamination
from wastewater.
9. Which device is used to measure well yield during pumping tests?
A. Anemometer
B. Flow meter
C. Seismograph
D. Hygrometer
B. Flow meter
Rationale: Flow meters provide accurate measurements of water
discharge from a well.
10. Artesian wells occur when:
A. Water flows uphill naturally due to pressure
B. The aquifer is unconfined
C. Water table is below the pump
