Table Of ContentContents
PREFACE xiii
PART ONE
THE HYDROLOGIC
CYCLE
CHAPTER 1
lntroduction
1 . 1
t.2
r.3
t.4
1.5
1.6
I.7
1.8
CHAPTER 2
Precipitation
2.1
2.2
2.3
2,4
2.5
2.6
2.7
Hydrology Defined
3
A Brief History
3
The Hydrologic Cycle
5
The Hydrologic Budget
5
Hydrologic Models
11
Hydrologic Data
11
Common Units of Measurement
12
Application of Hydrology to Environmental Problems
t2
1 5
Water Vapor
15
Precipitation
17
Distribution of the Precipitation Input
Point Precipitation
27
Areal Precipitation
29
Probable Maximum Precipitation
34
Gross and Net PreciPitation
36
vi
coNTENTS
CHAPTER 3
Interception
and Depression
Storage
40
3.1
Interception
40
3.2
Throughfall
44
3.3
Depression Storage
45
CHAPTER 4
Infiltration 52
4.I
Measuring Infiltration
53
4.2
Calculation of Infiltration
53
4.3
Horton's Infiltration Model
57
4.4
Green-AMPT Model
64
4.5
Huggins-Monke Model
67
4.6
Holtan Model
68
4.7
Recovery of Infiltration Capacity
69
4.8
Temporal and Spatial Variability of Infiltration Capacity
70
4.9
SCS Runoff Curve Number Procedure
73
4.10
@ Index
76
CHAPTER 5
Evaporation
and Transportation 82 "
5.1
Evaporation
86
5.2
Estimating Evaporation
86
5.3
Evaporation Control
95
5.4
Transpiration
95
5.5
Transpiration Control
100
5.6
Evapotranspiration
100
5.7
Estimating Evapotranspiration
103
CHAPTER 6
Streamflow 11 1
6.1
Drainage Basin Effects
111
6.2
The Hydrograph
11,2
6.3
Units of Measurement for Streamflow
113
6.4
Measuring and Recording Streamflow
113
6.5
Measurements
of Depth and Cross-Sectional
Area
II4
6.6
Measurement of Velocity
lI4
6.7
Relating Point Velocity to Cross-Sectional Flow Velocity
115
6.8
The Slope-Area Method for Determining Discharge
II7
oONTENTS Vii
PART TWO
HYDROLOGIG
fT'IEASUREMENTS
AND MONITORING
CHAPTER 7
Hydrologic
Data Sources
123
7.1
General Climatological Data
I23
7.2
Precipitation Data
123
7.3
Streamflow Data
124
7.4
Evaporation and Transpiration Data
I24
CHAPTER 8
f nstrumentation 126
8.1
Introduction
126
8.2
HYdrologic Instruments
127
8.3
Telemetry SYstems
135
8.4
Remote Sensing
135
CHAPTER 9
Monitoring
Networks 144
121
9.r
9.2
9.3
9.4
The Purpose of Monitorin g
144
Special Considerations
I45
Uie of ComPuters in Monitoring
I47
Hydrological-Meteorlogical Networks
147
PART THREE
SURFACE WATER HYDROLOGY 151
CHAPTER
1O
Runoff and the Catchnient 153
10.1
Catchments, Watersheds, and Drainage Basins
tO.2
Basin Characteristics Affecting Runoff
155
10.3
RudimentaryPrecipitation-RunoffRelationships
IO.4
Streamflow Frequency Analysis
166
10.5
StreamflQw Forecasting
168
CHAPTER 1 1
Hydrographs 171
11.1
Streamflow HYdrograPhs
171
Il.2
Factors Affecting Hydrograph Shape
172
11.3
HydrograPh ComPonents
174
153
164
viii
ooNTENTS
lI.4
Base Flow Separation
I77
11.5
Hydrograph Time Relationships
181
11.6
Time of Concentration
I82
Il.7
Basin Lae Time
I82
CHAPTER
12
Unit Hydrographs 188
l2.I
Unit Hydrograph Definition
188
12.2
Derivation of Unit Hydrographs from Streamflow Data
190
12.3
Unit Hydrograph Applications by Lagging Methods
I94
12.4
S-Hydrograph Method
198
12.5
The Instantaneous Unit Hydrograph
201
12.6
Synthetic Unit Hydrographs
205
CHAPTER
13
Hydrograph
Routing
234
13.1
Hydrologic River Routing
235
13.2
Hydrologic Reservoir Routing
245
13.3
Hydraulic River Routing
248
CHAPTER
14
Snow Hydrology
265
I4.l
Introduction
265
I4.2
Snow Accumulation and Runoff
267
I4.3
Snow Measurements and Surveys
268
I4.4
Point and Areal Snow Characteristics
269
14.5
The Snowmelt Process
271.
14.6
Snowmelt Runoff Determinations
284
CHAPTER
15
Urban and Small Watershed
Hydrology 309
15.1
Introduction
309
15.2
Peak Flow Formulas for Urban Watersheds
311
i5.3
Peak Flow Formulas for Small Rural Watersheds
33I
15.4
Runoff Effects of Urbanization
344
CHAPTER
16
Hydrologic
Design
359
16.l
Hydrologic Design Procedures
360
16.2
Data for Hydrologic Design
363
CONTENTS
IX
16.3
16.4
16.5
t6.6
16.7
16.8
1 8 . 1
t8.2
18.3
18.4
18.5
18.6
r8.7
18.8
18.9
1 8 . 1 0
1 8 . 1 1
18.t2
Hydrologic Design-Frequency
Criteria
Design Storms
373
Critical Event Methods
391
Airport Drainage Design
400
Design of Urban Storm Drain Systems
Floodplain Analysis
409
Hydrostatics
435
Groundwater Flow
436
Darcy's Law
436
Permeability
438
Velocity Potential
440
Hydrodynamic Equations
441
' Flowlines and Equipotential Lines
Boundary Conditions
447
Flow Nets
449
Variable Hydraulic Conductivity
Anisotropy
452
Dupuit's Theory 453
365
402
PART FOUR
GROUNDWATER
HYDROLOGY 425
CHAPTER
17
Groundwater,
Soils, and Geology
427
l7.l
Introduction
427
I7.2
Groundwater Flow-General Properties
429
I7.3
Subsurface Distribution of Water
429
I7.4
Geologic Considerations
430
I7.5
Fluctuations in Groundwater Level
433
I7.6
Groundwater-Surface
Water Relations
433
CHAPTER
18
Mechanics
of Flow
435
444
451
CHAPTER
19
Wells and Collection
Devices
19.1
19.2
19.3
19.4
19.5
460
Flow to Wells
460
Steady Unconfined Radial Flow Toward a Well
461
Steady Confined Radial Flow Toward a Well
462
Well in A Uniform Flow Field
463
Well Fields
465
X
CONTENTS
19.6
The Method of Images
466
I9.7
Unsteady Flow
467
19.8
Leaky Aquifers
4'13
I9.9
Partially Penetrating Wells
473
19.10
Flow to an Infiltration Gallery
473
19.ll
Saltwater Intrusion
474
19.12
Groundwater Basin Development
475
CHAPTER 20
Modeling Regional Groundwater
Systems
481
20.I
Regional Groundwater Models
481
20.2
Finite-Difference Methods
484
20.3
Finite-Element Methods
493
20.4
Model Applications
494
20.5
Groundwater Quality Models
500
PART FIVE
HYDROLOGIC
MODELING 505
CHAPTER
21
Introduction
to Hydrologic
Modeling
5O7
2l.I
Hydrologic Simulation
508
2t.2
Groundwater Simulation
509
21.3
Hydrologic Simulation Protocol
524
21.4
Corps of Engineers Simulation Models
526
CHAPTER 22
Synthetic Streamflows 535
22.I
Synthetic Hydrology
536
22.2
Serially Dependent Time Series Analysis
539
CHAPTER 23
Continuous
Simulation
Models
548
23.1
Continuous Streamflow Simulation Models
549
23.2
Continuous Simulation Model Studies
570
CHAPTER 24
Single-Event
Simulation
Models
594
24.1
Storm Event Simulation
594
24.2
Federal Agency Single-Event Models
597
24.3
Storm Surge Modeling
625
CHAPTER 25
Urban Runotf Simulation
Models
CONTENTS Xi
25.1
25.2
25.3
PART SIX
STATISTICAL
METHODS
630
Urban Stormwater System Models
63I
Urban Runoff Models Compared
659
Vendor-DevelopedUrbanStormwaterSoftware 663
669
CHAPTER 26
Probability
and Statistics
CHAPTER 27
Frequency
Analysis
APPENDICES
INDEX
757
751
671
Random Variables and Statistical Analysis
672
Concepts of Probability
673
ProbabilityDistributions
676
Moments of Distributions
681
Distribution Characteristics
682
Types of Probability Distribution Functions
685
ContinuousProbabilityDistributionFunctions 685
Bivariate Linear Regression and Correlation
690
Fitting Regression Equations
692
Regression and Correlation Applications
697
26.1
26.2
26.3
26.4
26.5
26.6
26.7
26.8
26.9
26.r0
27.1
27.2
27.3
27.4
27.5
27.6
27.7
708
Frequency Analysis
708
Graphical Frequency Analysis
709
Frequency Analysis Using Frequency Factors
7Il
Regional Frequency Analysis
7I9
Reliability of Frequency Studies
730
Frequency Analysis of Partial Duration Series
734
Flow Duration Analysis
737
Preface
Water management is taking on new dimensions. New federal thrusts, the grow-
ing list of global iisues, and strong public sentiment regarding environmental protec-
tion have been the principal driving forces.
In the early years of the 20th century, water resources development and manage-
ment were focuied almost exclusivd on water supply and flood control' Today, these
issues are still important, but protecting the environment, ensuring safe drinking
water, and providing aesthetic
-and
recriatioinal experiences compete equally for
attention and funds. Furthermore, an environmentally conscious public is pressing for
greater reliance on improved management practices, with fewer structural compo-
ients, to solve this nuiion'. water problems. The notion of continually striving to
provide more water has been replaced by one of husbanding this precious natural
resource.
There is a growing constituency for allocating water for the-benefit of fish and
wildlife, for protection-of marshes and estuary areas' and for other natural system
uses. But estimating the quantities of water needed for environmental protection and
for maintaining and/or restoring natural systems is difficult, and there are still many
unknowns. Scilntific data are ,putt", and our understanding of the complex interac-
tions inherent in ecosystems
of an scales is rudimentary. Indeed, this is a critical issue'
since the quantities of water involved in environmental protection can be substantial
and competition for these waters from traditional water users is keen' The nations of
the world are facing major decisions regarding natural systems-decisions that are
laden with significant ectnomic and social impacts. Thus there is_an urgency associ-
ated with developing a better understanding of ecologic systems and of their hydrologic
components.
Water policies of the future must therefore take on broader dimensions' More
emphasis must be placed on regional planning and management, and regional institu-
tions to accommodate this muJt be devised. Water management must be practiced at,
and between, all levels of government. Land use and water use planning must be more
tightly coordinated as well'
XIV
PREFACE
Water scientists and engineers of tomorrow must be equipped to address a
diversity of issues such as: the design and operation of data retrieval and storage
systems; forecasting; developing alternative water use futures; estimating water re-
quirements for natural systems; exploring the impacts of climate change; developing
more efficient systems for applying water in all water-using sectors; and analyzing and
designing water management systems incorporating technical, economic, environ-
mental, social, legal, and political elements. A knowledge of hydrologic principles is
a requisite for dealing with such ibsues.
This fourth edition has been designed to meet the contemporary needs of water
scientists and engineers. It is organized to accommodate students and practitioners
who are concerned with the development, management, and protection of water
resources. The format of the book follows that of its predecessor,
providing material
for both an introductory and a more advanced course.
Parts One through Four provide the basics for a beginning level course, while
Parts Five and Six may be used for a more advanced course on hydrologic model-
ing. This fourth edition has been updated throughout, and many solved examples
have been added. In addition, new computer approaches have been introduced and
problem-solving techniques include the use of spreadsheets
as appropriate. New fea-
tures of each chapter include an introductory statement of contents and, at the conclu-
sion of the chapter, a summary of key points.
Many sources have been drawn upon to provide subject matter for this book,
and the authors hope that suitable acknowledgment has been given to them.
Colleagues and students are recognized for their helpful comments and reviews, par-
ticularly the following reviewers.
Gert Aron, The Pennsylvania State University
John W. Bird, University of Nevada-Reno
Istvan Bogardi, University of Nebraska
Ronald A. Chadderton, Villanova University
Richard N. Downer, University of Vermont
Bruce E. Larock, University of Califurnia-Davis
Frank D. Masch, University of Texas-San Antonio
Philip L. Thompson, Federal Highway Administration
A special note of thanks is due to Dr. John W. Knapp, President of the Virginia
Military Institute, coauthor of previous editions of this book, for his past contributions
and valuable guidance.
Warren Viessman. Jr.
Gary L. Lewis
PART ONE
THE HYDROLOGIC
CYCLE
L.
Chapter 1
lntroduction
I Prologue
The purPose of this chaPter is to:
. Define hydrology.
. -,.1L
, Give a brief niJiory of the evolution of this important earth science'
. State the fundamental equation ofhydrology'
. Demonstrate trow ffiofogic principle, "urib" applied to supplement decision
support systems for water and environmental management'
1.1 HYDROLOGY
DEFINED
Hydrologyisanearthscience'Itencompassestheoccuffence'distribution,move-
menr, and properties of the waters of the earth. A knowledge of hydrology is funda-
mentaltodecisionmutingp,o.",,e,*he,ewaterisu"ompon"nto.f.th.esystemof
concern. water and environmental issues are inextricably linked' and it is important
toclear$understandhowwaterisaffectedbyandhowwateraffectsecosystem
maniPulations'
1.2 A BRIEF HISTORY
Ancient philosophers focused their i
Production of surface water flows
oc"ur."n"e of water in various stag
from the sea to the atmosPhere to t
early speculation was often faulty'l
of large subterranean reservoirs th
is interesting to note, however' tha
*suoeriornumbersindicatereferencesattheendofthechapter.
CHAPTER 1 INTRODUCTION
Greek aqueducts on both conveyance cross section and velocity. This knowledge was
lost to the Romans, and the proper relation between area, velocity, and rate of flow
remained unknown until Leonardo da Vinci rediscovered it duringihe Italian Renais-
sance.
During the first century s.c. Marcus Vitruvius, in Volume 8 of his treatise De
Architectura Libri Decem (the engineer's chief handbook during the Middle Ages),
set forth a theory generally considered to be the predecessor of modern notions of the
hydrologic cycle. He hypothesized that rain und ,no* falling in mountainous areas
infiltrated the earth's surface and later appeared in the lowlands as streams and
springs.
In spite of the inaccurate theories proposed in ancient times, it is only fair to state
that practical application of various try-orotogic
principles was often carried out with
considerable success. For example, about 4000 s.c. u du- was constructed across the
Nile to permit reclamation of previously barren lands for agricultural production.
Several thousand years later a canal to convey fresh water from Cairo io Suez was
built. Mesopotamian towns were protected uguinrt floods by high earthen walls. The
Greek and Roman aqueducts and early Chinese irrigation and flood control works
were also significant projects.
Near the end of the fifteenth century the trend toward a more scientific approach
to hydrology based on the observation of hydrologic phenomena became evident.
Leonardo da Vinci and Bernard Palissy independe-ntly
reached an accurate under-
standing of the water cycle. They apparently bised theii theories more on our"*iion
than on purely philosophical reasoning. Nevertheless,
until the seventeenth century it
seems evident that little if any effort was directed toward obtaining quantitative
measurements of hydrologic variables.
The advent of what might be called the "modern" science of hydrology is usually
considered to begin with the studies of such pioneers as Perrault, Mariotte, and Halley
in the seventeenth century.r'a Perrault obtained measurements
of rainfall in the Seine
River drainage basin over a period of 3 years. Using these and measurements of
runoff, and knowing,the drainage area size, he showeJ that rainfall was adequate in
quantity to account for river flows. He also made measurements of evaporati,on and
capillarity. Mariotte gauged the velocity of flow of the River Seine. Recorded veloc-
ities were translated into terms of dischirge by introducing measurements
of the river
cross section' The English astronomer Halley measured the rate of evaporation of the
Mediterranean Sea and concluded that the amount of water evaporated was sufficient
to account for the outflow of rivers tributary to the sea. Measurements such as these,
although crude, permitted reliable conclusions to be drawn reggrding the hydrologic
phenomena being studied.
brth numerous advances in hydraulic theory
zometer, the Pitot tube, Bernoulli's theorem,
ples.8
perimental hydrology flourished. Significant
ydrology and in the measurement of surface
water. Such significant contributions as Hagen-Poiseuille's capillary flow equation,
Darcy's law of flow in porous media, und th" Dupuit-Thiem well formula were
evolved'e-lr The beginning of systematic stream guoling can also be traced to this
period' Although the basis for modern hydrology wui tirrr established in the nine-
,)
1.4 THE HYDROLOGIC
BUDGET
5
1.3
teenth century, much of the effort was empirical in nature. The fundamentals of
physical hydtotogy had not yet been well established or widely recognized. In the early
years of tle twJntieth ""niury the inadequacies of many earlier empirical formula-
tions became well known. As a result, interested governmental agencies began to
develop their own programs of hydrologic research' From about 1930 to 1950, rational
analysis began to ieplace empiricism.3 Sherman's unit hydrograph, Horton's
infiltration theory, und Th"it's nonequilibrium -approach to well hydraulics are out-
standing examples of the great progress made'r2-'o
Since 1930 a theoreiical approach to hydrologic problems has largely replaced
less sophisticated methods of ttre past. Advances in scientific knowledge permit a
better understanding ofthe physicai basis ofhydrologic relations, and the advent and '
continued developnient of high-speed digital computers have made possible, in both
a practical and an economic iense, extensive mathematical manipulations that would -
have been overwhelming in the past.
For a more compiehensivi historical treatment, the reader is referred to the
works of Meinzer, Jonls, Biswas, and their co-workers'1'2'4'5'15
THE HYDROLOGIC
CYCLE
The hydrologic cycle is a continuous process by which water is transported from the
oceans to the atmosphere to the landind back to the sea. Many subcycles exist' The
evaporation of inlan-d water and its subsequent
precipitation over land before return-
ingio the ocean is one example. The driving force for the global water transport system
is provided by the sun, which furnishes the energy required for evaporation' Note that
the water quality also changes during passage through the cycle; for example, sea
water is converted to fresh water through evaporation'
The complete water cycle is global in nature. world water problems require
studies on regional, national, internitional, continental, and global scales.16
Practical
significance of the fact that the total supply of fresh water available to the earth is
limited and very small compared with ihe salt water content of the oceans has
received little attention. Thus waters flowing in one country cannot be available at the
same time for use in other regions of the world. Raymond L' Nace of the u's'
Geological Survey has aptly sta=ted
thatoowater resources are a global problem with
local roots."tu Mtdern hydrologists are obligated to cope with problems requiring
definition in varying scales of oider of magnitude difference. In addition, developing
techniques to contiol weather must receive careful attention, since climatological
changes in one area can profoundly affect the hydrology and therefore the water
resources of other regions.
THE HYDROLOGIC
BUDGET
Because the total quantity of water available to the earth is finite and indestructible,
the global hydrolojic ,yrt"* may be looked upon as closed. Open hydrologic subsys-
tems are abundantlhowever, and these are usually the type analyzed' For any system'
' a water budget can be developed to account for the hydrologic components'
1 . 4
CHAPTER 1 INTRODUCTION
Figures I'I,I.2, and 1.3 show a hydrologic budget for the coterminous United
States, a conceptualized hydrologic cycle, and the distribution of a precipitation input,
respectively. These figures illustrate the components of the water cycle with which a
hydrologist is concerned. In a practical sense, some hydrologic region is dealt with and
a budget for that region is established. Such regions may be topographically defined
(watersheds and river basins are examples), politically specified (e.g- couniy or city
limits), or chosen on some other grounds. Watersheds or drainagi tasins are the
easiest to deal with since they sharply define surface water boundaries. These topo-
graphically determined areas are drained by a river/stream or system of connecting
rivers/streams such that all outflow is discharged through a single outlet. Unfortu-
nately, it is often necessary to deal with regions that are not well suited to tracking
hydrologic components. For these areas, the hydrologist will find hydrologic budgeting
somewhat of a challenge.
The primary input in a hydrologic budget is precipitation. Figures 1.1-1.3
illustrate this. Some of the precipitation (e.g., rain, snow, hail) may be intercepted by
trees, grass, other vegetation, and structural objects and will eventually return to the
,
atmosphere by evaporation. Once precipitation reaches the ground, some ofit may fill
depressions
(become depression storage), part may penetrale the ground (infiltraie) to
replenish soil moisture and groundwater reservoirs, and some may become surface
runoff-that is, flow over the earth's surface to a defined channel such as a stream.
Figure 1'3 shows the disposition ofinfiltration, depression storage, and surface runoff.
and vegetation
I '1.'
Consumptive
use
100 bgd
bgd = billion gallons per day
*r-d{i;
Figure 1.1 Hydrologic budget of cotermirious united States. (U.S. Geological survey.)
