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California Certified Hydrogeologist (CHG) Specialty
Licensing Exam | Latest Verified Questions and
Detailed Answers
OVERVIEW DESCRIPTION:
The California Certified Hydrogeologist (CHG) exam, formally the California Specific Exam
(CSE) for hydrogeology, is a rigorous, specialized licensing assessment for Professional
Geologists (PGs) seeking to demonstrate advanced expertise in groundwater science. Building on
the foundational knowledge of the ASBOG national exams, this state-specific test evaluates a
candidate's applied understanding of California's unique and complex hydrogeologic
frameworks, including its alluvial basins, coastal aquifers, and tectonically influenced systems.
The exam focuses on the practical application of groundwater hydraulics, water quality and
contaminant fate, well construction principles, and critical field methodologies. A significant
portion of the exam is dedicated to California's extensive regulatory landscape, including the
Sustainable Groundwater Management Act (SGMA), the Porter-Cologne Water Quality Control
Act, and relevant sections of the California Code of Regulations, ensuring that a CHG is fully
equipped to manage the state's vital groundwater resources responsibly and protect public health
and safety.
Groundwater Hydraulics & Hydrology
QUESTION 1
A confined aquifer has a hydraulic conductivity of 20 ft/day and an effective porosity of
0.2. If the hydraulic gradient is 0.0015, what is the approximate average linear
groundwater velocity?
A) 0.015 ft/day
B) 0.15 ft/day
C) 1.5 ft/day
D) 15 ft/day
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CORRECT ANSWER: B
EXPERT RATIONALE: Average linear velocity (v) is calculated by Darcy's Law: v = (K * i) /
n_e, where K is hydraulic conductivity, i is the gradient, and n_e is effective porosity.
Thus, v = (20 ft/day * 0.0015) / 0.2 = 0.15 ft/day.
QUESTION 2
When analyzing an aquifer test in a confined aquifer with a single pumping well and one
observation well, which analytical method is most appropriate for determining
transmissivity (T) and storativity (S)?
A) The Theis curve-matching method
B) The Cooper-Jacob straight-line method
C) The Hantush inflection point method
D) The Neuman curve-matching method
CORRECT ANSWER: A
EXPERT RATIONALE: The Theis method is a curve-matching technique suitable for
unsteady-state flow in confined aquifers and can be used with data from a single
observation well. The Cooper-Jacob method is a simplification valid for later time data
and large values of u.
QUESTION 3
In an unconfined aquifer, delayed gravity drainage causes a characteristic S-shaped
curve on a time-drawdown log-log plot. Which type of aquifer test analysis is specifically
designed to account for this phenomenon?
A) Theis recovery method
B) Cooper-Jacob method
C) Neuman method
D) Hantush-Jacob method
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CORRECT ANSWER: C
EXPERT RATIONALE: The Neuman method accounts for delayed gravity drainage (water
released from storage as the water table declines) in an unconfined aquifer, which
violates the instantaneous release assumption of the Theis method. It provides estimates
for both early (elastic) and late (gravity) time storage parameters.
QUESTION 4
If the radius of influence of a pumping well in a confined aquifer is 1,000 ft and the
drawdown at the well is 20 ft, what is the approximate drawdown at a distance of 100 ft
from the well, assuming steady-state conditions and using the Thiem equation?
A) 2 ft
B) 10 ft
C) 15 ft
D) 20 ft
CORRECT ANSWER: C
EXPERT RATIONALE: For steady-state radial flow to a well, drawdown is proportional to
the log of the distance. The approximate drawdown (s) at distance r is given by s = s_w *
[ln(r_0/r) / ln(r_0/r_w)]. Without the well radius (r_w), an exact number is difficult, but
drawdown decreases logarithmically, not linearly, so it will be significantly more than 2 ft
but less than 20 ft.
QUESTION 5
What does the storage coefficient (S) of a confined aquifer physically represent?
A) The volume of water an aquifer can hold
B) The volume of water released from storage per unit surface area per unit decline in
head
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C) The ratio of horizontal to vertical hydraulic conductivity
D) The specific yield of the aquifer material
CORRECT ANSWER: B
EXPERT RATIONALE: The storage coefficient (storativity) is defined as the volume of
water that an aquifer releases from or takes into storage per unit surface area of the
aquifer per unit change in head. For confined aquifers, this water comes from the
expansion of water and compression of the aquifer matrix.
QUESTION 6
A hydrogeologist is estimating groundwater recharge using the water-table fluctuation
method. Which data set is most critical for this analysis?
A) Daily precipitation data for the last 50 years
B) Continuous water-level measurements from a well penetrating the water table
C) Specific yield values from aquifer tests in confined aquifers
D) Streamflow gauging data from the nearest river
CORRECT ANSWER: B
EXPERT RATIONALE: The water-table fluctuation method relies on the principle that rises
in water table elevation in unconfined aquifers are due to recharge arriving at the water
table. Therefore, frequent (often daily) water-level measurements are essential to
capture the peaks and recessions.
QUESTION 7
Which of the following parameters is a measure of the capacity of a geologic material to
transmit a fluid, specifically defined as the discharge per unit hydraulic gradient per unit
width?
A) Transmissivity
B) Hydraulic conductivity
California Certified Hydrogeologist (CHG) Specialty
Licensing Exam | Latest Verified Questions and
Detailed Answers
OVERVIEW DESCRIPTION:
The California Certified Hydrogeologist (CHG) exam, formally the California Specific Exam
(CSE) for hydrogeology, is a rigorous, specialized licensing assessment for Professional
Geologists (PGs) seeking to demonstrate advanced expertise in groundwater science. Building on
the foundational knowledge of the ASBOG national exams, this state-specific test evaluates a
candidate's applied understanding of California's unique and complex hydrogeologic
frameworks, including its alluvial basins, coastal aquifers, and tectonically influenced systems.
The exam focuses on the practical application of groundwater hydraulics, water quality and
contaminant fate, well construction principles, and critical field methodologies. A significant
portion of the exam is dedicated to California's extensive regulatory landscape, including the
Sustainable Groundwater Management Act (SGMA), the Porter-Cologne Water Quality Control
Act, and relevant sections of the California Code of Regulations, ensuring that a CHG is fully
equipped to manage the state's vital groundwater resources responsibly and protect public health
and safety.
Groundwater Hydraulics & Hydrology
QUESTION 1
A confined aquifer has a hydraulic conductivity of 20 ft/day and an effective porosity of
0.2. If the hydraulic gradient is 0.0015, what is the approximate average linear
groundwater velocity?
A) 0.015 ft/day
B) 0.15 ft/day
C) 1.5 ft/day
D) 15 ft/day
,2|Page
CORRECT ANSWER: B
EXPERT RATIONALE: Average linear velocity (v) is calculated by Darcy's Law: v = (K * i) /
n_e, where K is hydraulic conductivity, i is the gradient, and n_e is effective porosity.
Thus, v = (20 ft/day * 0.0015) / 0.2 = 0.15 ft/day.
QUESTION 2
When analyzing an aquifer test in a confined aquifer with a single pumping well and one
observation well, which analytical method is most appropriate for determining
transmissivity (T) and storativity (S)?
A) The Theis curve-matching method
B) The Cooper-Jacob straight-line method
C) The Hantush inflection point method
D) The Neuman curve-matching method
CORRECT ANSWER: A
EXPERT RATIONALE: The Theis method is a curve-matching technique suitable for
unsteady-state flow in confined aquifers and can be used with data from a single
observation well. The Cooper-Jacob method is a simplification valid for later time data
and large values of u.
QUESTION 3
In an unconfined aquifer, delayed gravity drainage causes a characteristic S-shaped
curve on a time-drawdown log-log plot. Which type of aquifer test analysis is specifically
designed to account for this phenomenon?
A) Theis recovery method
B) Cooper-Jacob method
C) Neuman method
D) Hantush-Jacob method
,3|Page
CORRECT ANSWER: C
EXPERT RATIONALE: The Neuman method accounts for delayed gravity drainage (water
released from storage as the water table declines) in an unconfined aquifer, which
violates the instantaneous release assumption of the Theis method. It provides estimates
for both early (elastic) and late (gravity) time storage parameters.
QUESTION 4
If the radius of influence of a pumping well in a confined aquifer is 1,000 ft and the
drawdown at the well is 20 ft, what is the approximate drawdown at a distance of 100 ft
from the well, assuming steady-state conditions and using the Thiem equation?
A) 2 ft
B) 10 ft
C) 15 ft
D) 20 ft
CORRECT ANSWER: C
EXPERT RATIONALE: For steady-state radial flow to a well, drawdown is proportional to
the log of the distance. The approximate drawdown (s) at distance r is given by s = s_w *
[ln(r_0/r) / ln(r_0/r_w)]. Without the well radius (r_w), an exact number is difficult, but
drawdown decreases logarithmically, not linearly, so it will be significantly more than 2 ft
but less than 20 ft.
QUESTION 5
What does the storage coefficient (S) of a confined aquifer physically represent?
A) The volume of water an aquifer can hold
B) The volume of water released from storage per unit surface area per unit decline in
head
, 4|Page
C) The ratio of horizontal to vertical hydraulic conductivity
D) The specific yield of the aquifer material
CORRECT ANSWER: B
EXPERT RATIONALE: The storage coefficient (storativity) is defined as the volume of
water that an aquifer releases from or takes into storage per unit surface area of the
aquifer per unit change in head. For confined aquifers, this water comes from the
expansion of water and compression of the aquifer matrix.
QUESTION 6
A hydrogeologist is estimating groundwater recharge using the water-table fluctuation
method. Which data set is most critical for this analysis?
A) Daily precipitation data for the last 50 years
B) Continuous water-level measurements from a well penetrating the water table
C) Specific yield values from aquifer tests in confined aquifers
D) Streamflow gauging data from the nearest river
CORRECT ANSWER: B
EXPERT RATIONALE: The water-table fluctuation method relies on the principle that rises
in water table elevation in unconfined aquifers are due to recharge arriving at the water
table. Therefore, frequent (often daily) water-level measurements are essential to
capture the peaks and recessions.
QUESTION 7
Which of the following parameters is a measure of the capacity of a geologic material to
transmit a fluid, specifically defined as the discharge per unit hydraulic gradient per unit
width?
A) Transmissivity
B) Hydraulic conductivity
