Wednesday, 14 October 2009





This reference text is an expanded and updated version of the text by the same name published eight years
earlier. As such, this text is a compilation of many classical and more modern approaches to analyzing and
modeling subsurface flow and transport.
Since Darcy’s pioneering work well over a century ago, our qualitative and quantitative understanding
of the flow of water and transport of chemicals in the subsurface has soared to great heights.Much of our
current understanding of flow processes has been developed over the past 40 years, and our understanding
of transport processes has developed mainly over the last 25 years. Substantial recent advances have been
driven largely by two factors: (a) the development of inexpensive high-speed computing, and (b) the
international focus on environmental quality and global change.
Much of the groundwater work performed earlier in this century revolved around very simplistic
conceptualizations of the subsurface, simplifications that were so drastic as to allow analytical solutions
to flow problems and the subsequent development of type-curves. Consequently, well installation and
design, and groundwater maintenance revolved around such idealizations as homogeneity, isotropy, and
infinite domains, which as we all know, are completely unrealistic assumptions.
With the advent of computing in the 1960s, through its modern refinements in software and hardware,
and derivation of new sophisticated numerical algorithms, we have made a quantum leap forward in
our ability to predict the behavior of our groundwater resources. This, coupled with the tremendous
amount of research dollars, tied mainly to the environment, has led to a flood of research manuscripts,
new engineering tools, and commercially available groundwater flow and transport software.
Unfortunately, while we have made tremendous advances in our ability to model the subsurface, our
ability to cost-effectively measure material coefficients that go into the models has not kept pace. Thus,
modern models are full of uncertainty in input data, and hence, their output is uncertain. This uncertainty
has led to the introduction of stochastic tools to the field of subsurface hydrology.
This reference text is a compilation of many classical and more modern approaches to understanding
and modeling subsurface flow and transport. Chapters 1 through 4 provide an introduction to the subject.
In Chapter 1, the basic functions and terminology requisite to the study of flow and transport are
presented. This chapter also provides a historical background of the field. Subsequently, steady oneand
two-dimensional flow and transport (Chapter 2) and deterministic two- and three-dimensional flow
(Chapter 3) are discussed. Chapter 2 gives an overview of the occurrence of groundwater, while Chapters 3
and 4 present basic principles.
Flow and transport in geologic media are characterized by tremendous uncertainty in the geological
environment. One can safely say that in no other field of engineering are we faced with more complexity
and uncertainty than in groundwater flowand transport engineering.Uncertainty is dealtwith in a number
of different ways in Chapters 5, 8, 16, 18, and 19. Stochasticity in unsaturated flow and transport is dealt
with in Chapters 5 and 8, while Chapters 18 and 19 handle the stochastic saturated transport problem.
Interpolation via geostatistics is studied in Chapter 16. Deterministic unsaturated flow and transport
are handled in Chapters 6, 7, and 22, while Chapters 9, 12, 13, 20, 21, and 23 handle the saturated
problem. Chapters 9, 20, and 21 deal with preferential flow and fractures. Chapter 13 extends the classical
isothermal model to the nonisothermal case and Chapter 12 focuses on seawater intrusion. While most
chapters involve modeling to one degree or another, Chapters 23, 24, and 26 specifically focus on issues
related to modeling, such as verification and case studies. Chapters 14, 15, and 17 focus on characterizing
aquifers and contaminants.
Remediation or containment of contaminants in the subsurface has become critically important in
recent years. This involves observation, injection, and pumping well design and these topics are covered
in Chapters 10 and 11. Chapter 27 discusses sustaining our potable water. Landfill design and monitoring
are discussed in Chapters 33, 34, 35, and 37, while Chapters 36 and 37 focus on remediation strategies. In
remediation and containment strategies for contaminated sites and for water rights in general, legal issues
continually crop up and these are discussed in Chapter 32.
Most recently, climate change (Chapter 28) has come to the forefront of science. In the context of
groundwater, this has given rise to the field of echo-hydrology (Chapter 29) and the use of GIS (Chapter 30).
This revised text has been in the works for a little over two years. The authors are considered to be
among the best in their fields. All chapters have been peer-reviewed.

John H. Cushman
Department of Earth & Atmospheric Sciences
Department of Mathematics
Purdue University



Groundwater Monitoring 35-5
Plume of
extraction well (typ.)
monitor wells
Plan view
monitor wells
extraction well
Plume of
Cross section
Groundwater quality
monitoring well (typ.)
quality monitoring
well (typ.)
FIGURE 35.2 Performance monitoring of groundwater extraction system. (From USEPA, 1990. Handbook —
GroundWater, Volume I: GroundWater and Contamination. EPA/625/6-90/016a.Washington, DC.)
of petroleum products to the storage tank through underground pipes) that could also have an
adverse impact on groundwater quality?
• What regulationsgo vern the activity or activities, and what portionsof those regulationsaddr ess
either groundwater monitoring or potential impactst o groundwater quality?
• What specific requirementsdo the regulationsc ontain for planning groundwater monitoring
events, for sampling groundwater, for analyzing groundwater samples, and for evaluating data
from groundwater sampling events?
• Dothe regulationsc ontain specific requirementsfor action in the event that impactst o groundwater
quality are identified during the monitoring program?
Once applicable regulatory requirementsha ve been identified, a program can be developed for
addressing each applicable regulatory requirement. A useful tool for addressing the requirements is the
groundwater monitoring plan. Guidelinesfor developing a groundwater monitoring plan are presented
in Section 35.2.2.


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