CE 475 Introduction to Groundwater Flow
OBJECTIVES AND SCOPE
Objectives:
 To understand the processes of groundwater flow in an aquifer
 To introduce concept of modeling and models which enable the
forecasting of the aquifer’s response to planned activities
 To provide the students with the necessary tools they need for predicting
the behavior of local groundwater as well as a regional aquifer system,
which are subject to natural and man-made excitations
 To present practical examples which will be of use in groundwater
development and management.
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CE 475 Introduction to Groundwater Flow
Topics covered in the course include:
 The aquifer
 The essentially horizontal flow approximation
 Components of the groundwater balance
 The motion equation in confined and phreatic aquifers
 Storativity and mass balance equations for confined, phreatic and leaky
aquifers
 Boundary conditions
 The complete mathematical statement of a forecasting problem in aquifers
 Review of solution methods.
 Analytical models and applications
 Numerical models; finite difference method
 Model calibration and verification; example of application
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CE 475 Introduction to Groundwater Flow
Figure 1.1 Schematic representation of the hydrologic cycle
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CE 475 Introduction to Groundwater Flow
Figure 1.2 An engineering view of the hydrologic cycle.
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CE 475 Introduction to Groundwater Flow
Geologic Formations:
* Classification on the basis of water storing and transmitting
capability:
 Aquifer [water-bearing formation (bed, deposit, stratum),
groundwater reservoir, groundwater basin]
 Aquitard [semi-pervious (leaky) formation]
 Aquiclude [impermeable formation]
 Aquifuge [non-porous, impervious formation)
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CE 475 Introduction to Groundwater Flow
Geologic Formations:
*Classification based on the origin and physical properties

Consolidated formation (Rocks)
- Igneous rocks (granite, basalt)
- Sedimentary rocks (sandstone, lime stone)
- Metamorphic rocks (marble, quartzite)

Unconsolidated formation (soil)
* Gravel
* Sand
* Clay
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CE 475 Introduction to Groundwater Flow
Geologic
Formation
Water Storing
Capability
Water
Transmitting
Capability
Aquifer
Good
Good
Aquitard
Very poor, None
Fair
Aquiclude
Fair
None-Very Poor
Aquifuge
None
None
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CE 475 Introduction to Groundwater Flow
Figure 1.3 Subsurface distribution of water
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CE 475 Introduction to Groundwater Flow
Figure 1.4 Types of aquifers
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CE 475 Introduction to Groundwater Flow
Figure 1.5 Various simplified aquifer boundaries
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CE 475 Introduction to Groundwater Flow
Types of Interstices
The portion of subsurface geological formation not occupied by solid matter is
the void space. It is also called as pore space, pores, interstices, and fissures.
The interstices can be grouped in two classes:
 Original Interstices
 They are created by geological processes at the time the rock was formed,
mainly in sedimentary and igneous rocks
 Secondary Interstices
 They are developed after the rock was formed, mainly in the form of
fissures joints and solution passages
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CE 475 Introduction to Groundwater Flow
Figure 1.6 Various types of interstices
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CE 475 Introduction to Groundwater Flow
Roles (Main Functions) of Aquifers
Source of Water
 Renewable resource
 Non-Renewable resource
Storage Réservoir
 Aquifer storativity
 Porosity
Conduit
 Aquifer Transmissivity
Permeability, Hydraulic Conductivity
Filter
Control of Base Flow
Water Mine
 Nonrenewable resource
 One-time-reserve
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CE 475 Introduction to Groundwater Flow
Groundwater Budgets:
A groundwater system consists of a mass of water flowing through the pores or
cracks below the earth’s surface. This mass of water is in motion. Water is
constantly added to the system by recharge from precipitation, and water is
constantly leaving the system as discharge to surface water and as
evapotranspiration. The total amount of water entering, leaving, and being
stored in the system must be conserved. An accounting of all the inflows,
outflows, and changes in storage is called as water budget
Human activities affect the amount and rate of movement of water in the
system, entering the system, and leaving the system. The changes resulting from
human interventions must be accounted for in the calculation of the water
budget
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CE 475 Introduction to Groundwater Flow
Groundwater Balance
1. Groundwater Flow and Leakage
 Inflow and Outflow through Aquifer Boundaries
 Leakage through Semipervious Layers
2. Natural Replenishment from Precipitation
3. Return Flow from Irrigation and Precipitation
4. Artificial Recharge (to enhance infiltration)
 Surface spreading methods
 Artificial recharge through wells
 Induced recharge
5. River-Aquifer Interrelationships
6. Springs
7. Evapotranspiration
8. Pumpage and Drainage
9. Change in Storage
10. Regional Groundwater Balance
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CE 475 Introduction to Groundwater Flow
Figure 1.7 Schematic representation of unconfined ground water balance
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CE 475 Introduction to Groundwater Flow
Groundwater System
Inputs
Uncontrollable
Excitation
Cause
SYSTEM
Outputs
Response
Effect
Controllable
Desirable
Detection
1
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Undesirable
Identification
2
Prediction
3
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CE 475 Introduction to Groundwater Flow
 Uncontrollable Inputs:
 Natural Recharge from
- Precipitation
- Irrigation return flow
 Controllable Inputs:
 Policy Variables
- Pumping and Injection Schedules
- Artificial recharge
 Desirable Outputs:
 Reduction in Subsurface Outflow
 Undesirable Outputs:
 Drying of a wetland
 Drying of a spring
 System Characteristics:
 Aquifer Geometry
- Thickness
- Lateral extent
 Hydraulic Parameters
- Hydraulic conductivity
- Transmissivity
- Porosity
- Storage coefficient
- Specific yield
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CE 475 Introduction to Groundwater Flow
Groundwater Systems and Three Unique Problems:
1) The defection or the instrumentation problem:
The set of inputs to the system is unknown. It involves determining the inputs given both
the responses of the system and the system outputs. The determination of the recharge or
leakage in semi-confined or unconfined aquifers, from the response properties of the
aquifer system, is an example of instrument problem.
This problem is not considered an important problem in groundwater hydrology:
2) The identification or the inverse problem:
It involves determining the parameters, which govern the response of the system in
particular this, requires determining the coefficients of differential equation, which
describes the response of the system. The determination of the transmissivity and the
storage coefficient of a confined aquifer are typical examples.
Identification is an extremely important problem in groundwater hydraulics.
3) The prediction problem:
This requires the prediction of the fluctuating head in the aquifers, given a range of
groundwater recharge and pumpage patterns both in temporal and areal distribution, with
known geometry and properties of the aquifer.
Solving the prediction (forecasting) problem means solving a model in order to obtain the
future distribution of water levels, or of piezometric heads produced in a specified aquifer
with known geometry and properties by an anticipated natural replenishment and by any
planned schedule of future pumping and artificial recharge, as envisaged in a proposed
management scheme (Bear and Verruijt 1987, pp. 53).
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CE 475 Introduction to Groundwater Flow
Outputs
Inputs
Uncontrollable
Undesirable
SYSTEM
Controllable
Desirable
User Judgment
Outputs
Inputs
Uncontrollable
Controllable
Undesirable
SYSTEM
Desirable
Judgment
Description
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