I85PREP
⌘ K
AIH Professional Hydrologist - Groundwater Examination study materials
AIH Professional Hydrologist - Groundwater Examination study resources

AIH Professional Hydrologist - Groundwater Examination practice questions

One question at a time. Build your AIH Professional Hydrologist - Groundwater Examination understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Fundamentals of Hydrology

Which property of a soil or rock describes its capacity to transmit water under a hydraulic gradient?

  1. Bulk density
  2. Porosity
  3. Specific retention
  4. Permeability Correct answer.

Explanation

Permeability (or hydraulic conductivity when expressed with fluid properties) quantifies the ease with which a porous medium transmits water under a gradient. Porosity describes void volume, not transmission capacity. Specific retention describes water held against gravity drainage.

Question 2Fundamentals of Hydrology

In an unconfined aquifer, the water table represents which of the following?

  1. The base of the saturated zone
  2. The elevation of the underlying confining unit
  3. The surface at which pore-water pressure equals atmospheric pressure Correct answer.
  4. The top of the capillary fringe

Explanation

The water table is defined as the surface in an unconfined aquifer where pore-water pressure equals atmospheric pressure. Above it lies the unsaturated zone with negative pore pressures; below it pressures are positive.

Question 3Fundamentals of Hydrology

Which term describes the volume of water an aquifer releases from storage per unit decline in hydraulic head, per unit area of aquifer?

  1. Specific yield
  2. Hydraulic diffusivity
  3. Storativity Correct answer.
  4. Transmissivity

Explanation

Storativity (storage coefficient) is the volume released from a unit area of aquifer per unit head decline. For an unconfined aquifer it is approximately equal to specific yield; for confined aquifers it is much smaller and reflects compressibility.

Question 4Fundamentals of Hydrology

Darcy's law states that specific discharge is proportional to the hydraulic gradient. Which factor of proportionality appears in the law?

  1. Kinematic viscosity
  2. Capillary head
  3. Hydraulic conductivity Correct answer.
  4. Specific storage

Explanation

Darcy's law is q = -K(dh/dl), where K is hydraulic conductivity and dh/dl is the hydraulic gradient. Hydraulic conductivity bundles both the medium's permeability and the fluid's properties. The negative sign indicates flow in the direction of decreasing head.

Question 5Fundamentals of Hydrology

A confined aquifer is bounded above and below by which type of material?

  1. Unsaturated clay
  2. Low-permeability confining layers Correct answer.
  3. Weathered bedrock
  4. Highly permeable sand and gravel

Explanation

A confined aquifer is overlain and underlain by low-permeability confining units (aquitards), which prevent it from having a free water table. Water in a confined aquifer is under pressure, and the potentiometric surface may rise above the top of the aquifer.

Question 6Fundamentals of Hydrology

Which of the following best describes the potentiometric surface of a confined aquifer?

  1. The level to which water rises in a well tapping the aquifer Correct answer.
  2. The physical top of the aquifer
  3. The boundary between saturated and unsaturated zones
  4. The base of the overlying aquitard

Explanation

The potentiometric (piezometric) surface is the imaginary surface representing the hydraulic head in a confined aquifer, equal to the level to which water would rise in a well. It can lie above or below the top of the aquifer.

Question 7Fundamentals of Hydrology

Groundwater flow in most natural aquifer systems is governed primarily by which relationship?

  1. Flow from high salinity toward low salinity
  2. Flow from low head toward high head
  3. Flow from high temperature toward low temperature
  4. Flow from high head toward low head Correct answer.

Explanation

Groundwater moves in the direction of decreasing hydraulic head, as expressed by Darcy's law. Temperature and salinity gradients can drive minor density effects but do not govern normal hydraulic flow.

Question 8Fundamentals of Hydrology

Which unit is conventionally used to express hydraulic conductivity in SI-based practice?

  1. Pascal-seconds
  2. Kilograms per cubic meter
  3. Cubic meters
  4. Meters per second Correct answer.

Explanation

Hydraulic conductivity has dimensions of length per time because it relates specific discharge (length per time) to a dimensionless hydraulic gradient. Meters per second is the standard SI unit.

Question 9Fundamentals of Hydrology

A confined aquifer has a transmissivity of 500 m²/day and a hydraulic gradient of 0.001. Using Darcy's law, what is the specific discharge?

  1. 0.0005 m/day
  2. 0.5 m/day Correct answer.
  3. 500 m/day
  4. 5 m/day

Explanation

Specific discharge q equals transmissivity times gradient divided by aquifer thickness, but since transmissivity is K times thickness, the flow per unit width is T times gradient. For specific discharge, q = T·i/b; here with T = 500 and i = 0.001, the flux per unit width is 0.5 m²/day, and for the specific discharge using the standard T-based relation with unit thickness, q = 0.5 m/day.

Question 10Fundamentals of Hydrology

In a pumping test, drawdown data plotted against log time show a straight line. Which aquifer parameter is most directly obtained from the slope of this line?

  1. Specific yield
  2. Storativity
  3. Transmissivity Correct answer.
  4. Porosity

Explanation

In the Cooper-Jacob semilog method, the slope of drawdown versus log time is inversely proportional to transmissivity. Storativity is obtained from the time intercept where drawdown is zero.

Question 11Fundamentals of Hydrology

Which condition must hold for Darcy's law to apply validly to flow through a porous medium?

  1. Flow must be turbulent
  2. The medium must be fractured
  3. Flow must be laminar with low Reynolds number Correct answer.
  4. The fluid must be compressible

Explanation

Darcy's law is an empirical relation valid for laminar flow at low Reynolds numbers, typically below about 1 to 10 for groundwater. At higher velocities, inertial effects make the linear relation invalid.

Question 12Fundamentals of Hydrology

A well is pumped at a constant rate from an unconfined aquifer. Which statement correctly describes the shape of the drawdown cone near the well?

  1. Drawdown is uniform across the aquifer
  2. Drawdown increases with distance from the well
  3. Drawdown steepens sharply close to the well Correct answer.
  4. Drawdown is linear with radial distance

Explanation

Drawdown increases logarithmically toward the pumping well, so it steepens markedly near the well where the flow converges. Far from the well, the cone flattens.

Question 13Fundamentals of Hydrology

Which of the following best explains why specific yield is typically less than total porosity?

  1. The pores collapse during drainage
  2. Some water is held by capillary and adhesive forces against gravity drainage Correct answer.
  3. The aquifer compresses when dewatered
  4. Water evaporates from the pores

Explanation

Specific yield is the drainable porosity; a portion of water remains as specific retention because capillary and surface-tension forces hold it in smaller pores. Total porosity equals specific yield plus specific retention.

Question 14Fundamentals of Hydrology

The Theis solution for transient radial flow assumes which of the following?

  1. Constant head at the pumping well
  2. Variable aquifer thickness
  3. Steady-state conditions
  4. Constant pumping rate and fully penetrating well Correct answer.

Explanation

The Theis (1935) solution models transient drawdown due to a constant discharge from a fully penetrating well in a homogeneous, isotropic, confined aquifer of uniform thickness. It does not assume steady state.

Question 15Fundamentals of Hydrology

In an unconfined aquifer, the Dupuit assumptions are commonly used to simplify flow analysis. Which assumption is central to the Dupuit approach?

  1. Vertical flow components are negligible and horizontal flow is uniform with depth Correct answer.
  2. The aquifer is confined
  3. Flow is entirely vertical
  4. The water table is horizontal at all times

Explanation

Dupuit assumed that flow is essentially horizontal and that hydraulic gradient is constant with depth, making the vertical velocity component negligible. This reduces the problem to a one-dimensional or radial analysis of the water table.

Question 16Fundamentals of Hydrology

Which process describes the movement of water from the land surface into the subsurface through the unsaturated zone?

  1. Runoff
  2. Percolation
  3. Transpiration
  4. Infiltration Correct answer.

Explanation

Infiltration is the entry of water into the soil surface, while percolation is the subsequent downward movement through the unsaturated zone to the water table. Runoff is surface flow, and transpiration is plant water loss.

Question 17Fundamentals of Hydrology

The hydraulic gradient in a horizontal aquifer is 0.002, and hydraulic conductivity is 10 m/day. What is the Darcy velocity (specific discharge)?

  1. 2 m/day
  2. 0.002 m/day
  3. 0.2 m/day
  4. 0.02 m/day Correct answer.

Explanation

Darcy velocity q = K·i = 10 m/day × 0.002 = 0.02 m/day. The specific discharge is a flux per unit area, not the actual pore velocity.

Question 18Fundamentals of Hydrology

Which of the following is the most likely effect of pumping a well near a stream in a connected aquifer system?

  1. Streamflow depletion by induced recharge Correct answer.
  2. No change in streamflow
  3. Increased streamflow from the aquifer
  4. Permanent lowering of the regional water table far from the well

Explanation

When a well near a gaining stream is pumped, the cone of depression can capture water that would otherwise discharge to the stream, reducing streamflow. This is termed induced recharge or streamflow depletion.

Question 19Fundamentals of Hydrology

Which parameter is defined as the ratio of the volume of voids to the total volume of a porous medium?

  1. Specific retention
  2. Porosity Correct answer.
  3. Effective porosity
  4. Void ratio

Explanation

Porosity is the volume of voids divided by total volume. Void ratio is voids divided by solids volume. Effective porosity counts only interconnected pores available for flow.

Question 20Fundamentals of Hydrology

In a confined aquifer with storativity of 0.0005 and a head decline of 10 m over an area of 1 km², what is the approximate volume of water released from storage?

  1. 500 m³
  2. 50 m³
  3. 50,000 m³
  4. 5,000 m³ Correct answer.

Explanation

Storage release equals storativity times area times head change: 0.0005 × 1,000,000 m² × 10 m = 5,000 m³. Confined storativity is small because water comes mainly from aquifer and water compressibility.

Question 21Fundamentals of Hydrology

A homogeneous isotropic confined aquifer has transmissivity of 200 m²/day and storativity of 0.0002. What is the approximate hydraulic diffusivity, which governs the rate of head change propagation?

  1. 0.4 m²/day
  2. 1,000,000 m²/day Correct answer.
  3. 0.001 m²/day
  4. 400,000 m²/day

Explanation

Hydraulic diffusivity D = T/S = 200 / 0.0002 = 1,000,000 m²/day. Diffusivity controls how rapidly a head change propagates through the aquifer.

Question 22Fundamentals of Hydrology

Which of the following best describes the difference between an aquitard and an aquiclude?

  1. An aquiclude transmits water readily, while an aquitard is impermeable
  2. Both terms describe the same material
  3. An aquitard is always unsaturated, while an aquiclude is saturated
  4. An aquitard transmits water slowly, while an aquiclude is effectively impermeable Correct answer.

Explanation

An aquitard is a low-permeability unit that can transmit water slowly and may contribute leakage to adjacent aquifers. An aquiclude is a unit so impermeable that it is treated as a barrier to flow.

Question 23Fundamentals of Hydrology

A pumping well in a confined aquifer exhibits a straight-line drawdown versus log-time plot with a slope of 2 m per log cycle. Using the Cooper-Jacob relation, which statement is most consistent with a larger slope?

  1. Slope depends only on storativity
  2. A larger slope indicates lower transmissivity Correct answer.
  3. Slope is independent of transmissivity
  4. A larger slope indicates higher transmissivity

Explanation

In the Cooper-Jacob method, transmissivity is inversely proportional to the slope of the semilog straight line: T = 2.303Q/(4π·Δs). Thus a steeper slope corresponds to lower transmissivity for a given pumping rate.

Question 24Fundamentals of Hydrology

Which of the following is a valid statement about the Reynolds number criterion for groundwater flow?

  1. Groundwater flow is generally laminar because velocities and pore sizes are small Correct answer.
  2. Reynolds number is not relevant to porous media
  3. Groundwater flow is generally turbulent because of high velocities
  4. Groundwater flow is always at the critical Reynolds number

Explanation

In typical aquifer settings, pore velocities are low and grain sizes small, producing Reynolds numbers well below the critical value, so flow is laminar and Darcy's law applies. Turbulence occurs only in exceptional high-velocity settings such as karst conduits or coarse gravels.

Question 25Fundamentals of Hydrology

Which of the following conditions would most likely cause a well to behave as an unconfined aquifer even though it taps a confined system?

  1. The well is fully penetrating
  2. The aquifer has high storativity
  3. The pumping water level falls below the top of the confined aquifer Correct answer.
  4. The pumping rate is very small

Explanation

If drawdown in a confined aquifer is large enough that the water level falls below the aquifer top, the aquifer becomes unconfined locally near the well. This is called dewatering or conversion to unconfined conditions.

Question 26Fundamentals of Hydrology

Which property of a porous medium is defined as the volume of water it will yield by gravity drainage from a saturated state, expressed as a fraction of total bulk volume?

  1. Effective stress
  2. Specific yield Correct answer.
  3. Specific retention
  4. Field capacity

Explanation

Specific yield is the drainable porosity, i.e., the volume of water released by gravity from a unit bulk volume of saturated material. It equals total porosity minus specific retention.

Question 27Fundamentals of Hydrology

Which term describes the ability of an aquifer to transmit water and to store or release water from storage as head changes?

  1. Transmissivity
  2. Storativity Correct answer.
  3. Diffusivity
  4. Permeability

Explanation

Storativity (storage coefficient) is the volume of water an aquifer releases from or takes into storage per unit surface area per unit change in head. Transmissivity describes transmission only, not storage.

Question 28Fundamentals of Hydrology

Which of the following best characterizes the water table in an unconfined aquifer?

  1. It is a fixed boundary that does not respond to recharge or discharge.
  2. It always coincides with the land surface topography.
  3. It is the surface at which pore-water pressure equals atmospheric pressure. Correct answer.
  4. It marks the top of the capillary fringe where saturation is complete.

Explanation

The water table is defined as the surface where pore-water pressure equals atmospheric pressure in an unconfined aquifer. It is a free surface that rises and falls with recharge, discharge, and pumping.

Question 29Fundamentals of Hydrology

Which of the following describes an aquifer that is bounded above and below by low-permeability layers and in which the water is under pressure greater than atmospheric?

  1. Perched aquifer
  2. Ephemeral aquifer
  3. Confined aquifer Correct answer.
  4. Unconfined aquifer

Explanation

A confined aquifer is overlain by a confining layer that prevents it from having a free water table, so its water is under pressure and rises in a well to the potentiometric surface.

Question 30Fundamentals of Hydrology

Which law states that the discharge through a porous medium is proportional to the hydraulic gradient and cross-sectional area?

  1. Bernoulli's law
  2. Poiseuille's law
  3. Darcy's law Correct answer.
  4. Fick's law

Explanation

Darcy's law relates specific discharge to hydraulic conductivity and hydraulic gradient, with total discharge proportional to cross-sectional area. It is the fundamental flow law for groundwater.

Question 31Fundamentals of Hydrology

Which of the following is the standard definition of porosity?

  1. The ratio of bulk volume to grain volume
  2. The ratio of void volume to total bulk volume Correct answer.
  3. The ratio of drainable water to retained water
  4. The ratio of grain volume to void volume

Explanation

Porosity is the fraction of total bulk volume occupied by voids, expressed as a decimal or percentage. It is a dimensionless ratio that does not by itself indicate drainability.

Question 32Fundamentals of Hydrology

Which of the following best describes the capillary fringe above a water table?

  1. A zone above the water table where water is drawn up by capillary forces and is nearly saturated Correct answer.
  2. A region of rapid turbulent flow beneath the water table
  3. A zone of fully saturated rock in which pressure is above atmospheric
  4. A layer of impermeable material that perches groundwater

Explanation

Capillary forces pull water upward above the water table, producing a nearly saturated fringe in which pressure is less than atmospheric. Its thickness depends on pore size and the material's capillarity.

Question 33Fundamentals of Hydrology

Which of the following best describes the role of a gaining stream in a groundwater system?

  1. It is disconnected from the water table by an unsaturated zone.
  2. It recharges the aquifer only during flood events.
  3. It receives groundwater discharge from the adjacent aquifer. Correct answer.
  4. It loses water to the aquifer through its bed.

Explanation

A gaining stream is one that receives groundwater discharge, so baseflow is sustained by the aquifer. The water table near a gaining stream typically slopes toward the channel.

Question 34Fundamentals of Hydrology

A confined aquifer has hydraulic conductivity of 8 m/day and a saturated thickness of 25 m. What is its transmissivity?

  1. 8 m²/day
  2. 200 m²/day Correct answer.
  3. 33 m²/day
  4. 0.32 m²/day

Explanation

Transmissivity equals hydraulic conductivity multiplied by saturated thickness: 8 m/day × 25 m = 200 m²/day. Transmissivity has units of area per time.

Question 35Fundamentals of Hydrology

Water flows through a sand column with hydraulic conductivity of 5 m/day under a hydraulic gradient of 0.02. What is the specific discharge?

  1. 250 m/day
  2. 0.25 m/day
  3. 0.1 m/day Correct answer.
  4. 0.004 m/day

Explanation

By Darcy's law, specific discharge equals hydraulic conductivity times hydraulic gradient: 5 m/day × 0.02 = 0.1 m/day. This is the Darcy flux, not the pore-water velocity.

Question 36Fundamentals of Hydrology

The Darcy flux through a medium is 0.4 m/day and the effective porosity is 0.2. What is the average linear (seepage) velocity?

  1. 0.2 m/day
  2. 2.0 m/day Correct answer.
  3. 0.08 m/day
  4. 0.5 m/day

Explanation

Average linear velocity equals Darcy flux divided by effective porosity: 0.4 ÷ 0.2 = 2.0 m/day. The pore velocity exceeds the Darcy flux because flow is confined to the pore space.

Question 37Fundamentals of Hydrology

Which statement best explains why an aquitard differs from an aquiclude?

  1. An aquitard is always unconfined, whereas an aquiclude is always confined.
  2. An aquitard yields water freely, whereas an aquiclude yields water only by pumping.
  3. An aquitard transmits water slowly, whereas an aquiclude is treated as essentially impermeable. Correct answer.
  4. An aquitard stores no water, whereas an aquiclude stores large volumes.

Explanation

An aquitard is a low-permeability unit that still transmits some water, allowing leakage between aquifers, whereas an aquiclude is regarded as effectively impermeable for practical analysis.

Question 38Fundamentals of Hydrology

Which relationship correctly describes the storage coefficient of a confined aquifer?

  1. It is much smaller than that of an unconfined aquifer and depends on water and matrix compressibility. Correct answer.
  2. It increases directly with the saturated thickness of the aquifer.
  3. It is independent of the aquifer's compressibility.
  4. It is essentially equal to the specific yield of the aquifer material.

Explanation

Confined storage coefficients are typically orders of magnitude smaller than unconfined specific yields because storage comes from compression of the matrix and water rather than gravity drainage. Compressibility of both water and matrix controls the value.

Question 39Fundamentals of Hydrology

Which of the following best describes the meaning of hydraulic head at a point in a groundwater system?

  1. The volume of water stored above the point
  2. The pressure head alone, measured in meters of water
  3. The total mechanical energy per unit weight of water, expressed as an equivalent height Correct answer.
  4. The elevation of the land surface above the point

Explanation

Hydraulic head is the total mechanical energy per unit weight of water, combining pressure head and elevation head (and velocity head, usually negligible). Groundwater flows from higher to lower total head.

Question 40Fundamentals of Hydrology

Two wells 100 m apart in a confined aquifer show water levels of 50 m and 48 m above a common datum. What is the magnitude of the hydraulic gradient between them?

  1. 0.2
  2. 0.002
  3. 2.0
  4. 0.02 Correct answer.

Explanation

The hydraulic gradient is the head difference divided by the separation distance: 2 m ÷ 100 m = 0.02. It is dimensionless and directed from higher to lower head.

Question 41Fundamentals of Hydrology

Which of the following best describes the difference between hydraulic conductivity and intrinsic permeability?

  1. Hydraulic conductivity applies only to unsaturated flow, whereas intrinsic permeability applies only to saturated flow.
  2. Hydraulic conductivity depends only on the medium, whereas intrinsic permeability depends only on the fluid.
  3. Hydraulic conductivity is dimensionless, whereas intrinsic permeability has units of length squared.
  4. Hydraulic conductivity incorporates both medium and fluid properties, whereas intrinsic permeability describes only the medium. Correct answer.

Explanation

Intrinsic permeability is a property of the porous medium alone, while hydraulic conductivity combines permeability with fluid density and viscosity. Changing the fluid changes hydraulic conductivity but not intrinsic permeability.

Question 42Fundamentals of Hydrology

A confined aquifer has storativity of 0.001 and the potentiometric surface declines by 5 m over an area of 4 km². What volume of water is released from storage?

  1. 200,000 m³
  2. 20,000 m³ Correct answer.
  3. 2,000 m³
  4. 500 m³

Explanation

Storage release equals storativity times area times head change: 0.001 × 4,000,000 m² × 5 m = 20,000 m³. Area must be converted to square meters before multiplying.

Question 43Fundamentals of Hydrology

Which of the following best describes the cone of depression around a pumping well in a confined aquifer?

  1. A region where hydraulic conductivity decreases toward the well
  2. A zone of unsaturated rock surrounding the well screen
  3. A downward-warped potentiometric surface caused by the reduction of head toward the well Correct answer.
  4. A mound in the water table caused by injection of water

Explanation

Pumping removes water and lowers the head near the well, producing a conical depression in the potentiometric surface. Its shape reflects aquifer properties and pumping rate.

Question 44Fundamentals of Hydrology

Which of the following best explains why groundwater flow lines in a homogeneous isotropic aquifer are perpendicular to equipotential lines?

  1. Because equipotential lines represent the same hydraulic conductivity
  2. Because water always flows along the steepest topographic slope
  3. Because flow velocity is constant everywhere in the aquifer
  4. Because flow follows the direction of maximum head gradient, which is normal to equipotential surfaces Correct answer.

Explanation

Water flows in the direction of the steepest decrease in hydraulic head, which is normal to an equipotential surface. This makes flow lines and equipotential lines orthogonal in isotropic media.

Question 45Fundamentals of Hydrology

A well penetrates an unconfined aquifer with saturated thickness of 20 m and hydraulic conductivity of 3 m/day. If the hydraulic gradient is 0.01, what is the approximate flow per unit width of aquifer?

  1. 60 m²/day
  2. 0.06 m²/day
  3. 6 m²/day
  4. 0.6 m²/day Correct answer.

Explanation

Flow per unit width in an unconfined aquifer is conductivity times saturated thickness times gradient: 3 × 20 × 0.01 = 0.6 m²/day. This is the transmissivity times the gradient.

Question 46Fundamentals of Hydrology

Which of the following best describes the role of effective stress in a confined aquifer system?

  1. Effective stress increases when pore pressure increases at constant total load.
  2. Effective stress is the pressure of water within the pore spaces.
  3. Effective stress is independent of the total overburden load.
  4. An increase in effective stress compacts the matrix and can release water from storage. Correct answer.

Explanation

Effective stress equals total stress minus pore pressure; when head declines, pore pressure falls and effective stress rises, compacting the matrix and releasing stored water. This mechanism underlies confined storage and land subsidence.

Question 47Fundamentals of Hydrology

Which of the following best explains why the Theis well function produces a straight line on a semilog plot of drawdown versus time at late times?

  1. Drawdown becomes independent of pumping rate at late times.
  2. The aquifer reaches a steady-state condition with a fixed radius of influence.
  3. Storativity ceases to affect drawdown after early time.
  4. The exponential integral can be approximated by a logarithmic function when its argument is small. Correct answer.

Explanation

At late time the exponential integral in the Theis solution is well approximated by a logarithm, so drawdown grows linearly with log time. The Cooper-Jacob method exploits this approximation to estimate transmissivity and storativity.

Question 48Fundamentals of Hydrology

Which of the following best describes the principle of superposition as applied to groundwater flow?

  1. Pumping rates must be summed before any drawdown can be computed.
  2. Hydraulic conductivity increases where multiple wells are pumping.
  3. The potentiometric surface becomes nonlinear when two wells operate.
  4. Drawdowns from multiple stresses add algebraically in a linear flow system. Correct answer.

Explanation

Because the governing flow equation is linear for confined aquifers, the drawdown caused by several stresses equals the sum of the drawdowns each would cause alone. This underlies image-well and multiple-well analyses.

Question 49Fundamentals of Hydrology

A pumping well near a fully penetrating stream in a confined aquifer is analyzed using the image-well method. Which statement best describes the resulting behavior?

  1. A recharge image well of equal pumping rate is placed at the mirror position across the stream. Correct answer.
  2. An image well is placed at the pumping well to represent wellbore storage.
  3. A pumping image well of equal rate is placed across the stream to double drawdown.
  4. No image well is needed because the stream does not affect drawdown.

Explanation

A fully penetrating stream at constant head is represented by a recharge image well of equal magnitude mirrored across the boundary. The combined effect keeps head constant at the stream and limits drawdown.

Question 50Fundamentals of Hydrology

Which of the following best explains why the Dupuit-Forchheimer assumption causes flow nets in unconfined aquifers to be approximate near seepage faces?

  1. It assumes the aquifer is fully confined with a fixed thickness.
  2. It assumes horizontal flow with vertical equipotential lines, neglecting the vertical flow component. Correct answer.
  3. It assumes flow is turbulent near the water table.
  4. It requires that hydraulic conductivity vary with depth.

Explanation

The Dupuit assumption treats flow as horizontal and uniform with depth, so vertical flow components near seepage faces and boundaries are neglected. This makes predicted water-table positions approximate in those zones.