PREFACE
This book is a revised and slightly expanded version of my book "Hydrology", first published in 1974, and then revised in 1995. It is intended as a textbook for undergraduate Civil Engineering students taking the Hydrology course in English.
Hydrology has gained a great significance in recent decades with the expansion of the water resources development studies that are an important component of man's efforts in controlling the environment. Although information about the water on the earth is being collected for several centuries, only recently this information is transformed into a science and put into use in engineering studies. Hydrology, as a science that deals with the distribution, motion and properties of the water on the earth, plays an important part in these studies. Hydrologic studies are given an impetus by the rapid growth of the population, agriculture and industry.
In the book, hydrologic events are analyzed by a system approach, following various components of the hydrologic cycle. It is attempted to introduce the student to the recent developments in hydrologic measurements, and the applications of the methods of the system analysis and statistics. A balance is tried to be achieved between various deterministic and probabilistic approaches so that the student can have an idea about the possible methods of treatment of hydrologic problems. Solved problems are added at the end of each chapter to illustrate the use of the methods described in the text. An extensive list of references is given at the end of the book.
I would like to thank to Sevgi Ogun for her careful work in preparing the text on the computer, and to the owners and staff of Birsen Kitabevi for their cooperation. I extend my thanks to Prof. Dr. Beyhan Oguz who thoroughly reviewed the manuscript.
M.BAYAZIT
Istanbul, September 2001
CONTENTS
Preface
Chapter 1 IntroductIon
1.1.Definition of Hydrology 1
1.2.Role and Significance of Hydrology in
Civil Engineering 1
1.3.Methods of Hydrology 2
1.4.Hydrologic Cycle 4
1.5.Fundamental Equations of Hydrology 7
1.5. 1.Conservation of Mass 7
1.5.2. Conservation of Energy 9
1.6.Water Balance of Earth 9
1.7.Energy Balance of Earth 10
Examples 12
Chapter 2 Precipitation 14
2.1.Formation of Precipitation 14
2.1.1.Necessary Conditions for Precipitation 14
2.1.2.Artificial Rain 16
2.2.Precipitation Measurement 17
2.2.1.Measurement of Rainfall 17
2.2.2.Measurement of Snow 20
2.2.3.Measurement Errors 21
2.2.4.Gage Network 22
2.3.Analysis of Precipitation Records 22
2.3.1.Precipitation Mass Curve and Hyetograph 23
2.3.2.Homogeneity of Records 24
2.3.3.Filling the Missing Observations 25
2.3.4.Extrapolating the Records 26
2.3.5.Calculation of Areal Average Precipitation 26
2.3.6.Areal Distribution of Precipitation 28
2.3.7.Precipitation Depth-Area-Duration Analysis 30
2.3.8.Probable Maximum Precipitation 31
2.3.9.Distribution of Precipitation in Time 33
Examples 33
Chapter 3 Evaporation 39
3.1.Mechanism of Evaporation 39
3.2.Evaporation from Water Surface 40
3.3. Evaporation from Soil and Snow 44
3.4.Transpiration and Interception 45
3.5.Evapotranspiration Losses 46
3.5.1.Potential and Actual Evapotranspiration 46
3.5.2.Estimation of Potential Evapotranspiration 47
3.5.3.Estimation of Actual Evapotranspiration 50
3.5.4.Estimation of Daily Evapotranspiration 51
Examples 53
Chapter 4 Infiltration 56
4.1.Infiltration Capacity 56
4.2.Infiltration Rate 60
4.3.Infiltration Indices 61
Examples 63
Chapter 5 Groundwater 66
5.1.Zones of Water in the Soil 66
5.2.Unsaturated Zone 68
5.3.Saturated Zone 71
5.4.Recharge of Groundwater and Losses 73
5.5.Groundwater Flow 75
5.6.Flow in the Unsaturated Zone 79
5.7.Flow to Wells 82
5.7.1.Safe Yield of Groundwater 85
5.7.2.Hydraulics of Wells 83
5.8.Determination of Hydraulic Conductivity 86
Examples 90
Chapter 6 Streamflow Measurement and Analysis of Data 96
6.1.Measurement of Stage and Water Surface Slope 97
6.2.Velocity Measurements 100
6.3.Cross-section Measurements 103
6.4.Discharge Measurements 103
6.5.Rating Curve 105
6.6.Analysis of Streamflow Records 107
6.6. 1.Streamflow Gauging Network 107
6.6.2.Computation of Daily Flows 108
6.6.3.Hydrograph 110
6.6.4.Estimation of Flows at Ungauged Sites 110
6.6.5.Flow Duration Curve 110
6.6.6.Flow Mass Curve 112
Examples 114
Chapter 7 Surface Flow 117
7.1.Characteristics of a River Basin 117
7.2.Runoff Separation 121
7.3.Rainfall-Runoff Relationships 124
7.4.Rational Method 127
7.5.Runoff due to Snowmelt 128
7.6.Runoff Due to Snowmelt 130
7.7.Areal Distribution of Runoff in Turkey 132
Examples 133
Chapter 8 Hydrograph Analysis 137
8.1.Elements of a Hydrograph 137
8.2.Separation of Direct Runoff and Base Flow 141
8.3.River Basin as a System 143
8.4.Parametric Basin Model 144
8.5.Unit Hydrograph Theory 147
8.5.1.Definition of Unit Hydrograph 147
8.5.2.Unit Hydrograpb Derivation 149
8.5.3.Computation of Runoff from Rainfall by Unit Hydrograpb 153
8.5.4.Synthetic Unit Hydrographs 155
8.5.5.Instantaneous Unit Hydrograpb 156
8.5.6.Unit Hydrograpb Applications 158
8.6.Flood Routing 158
8.7.Reservoir Routing 163
Examples 164
Chapter 9 Applieations of Probability Theory and Statistics in Hydrology 178
9.1.Definitions 179
9.2.Probability 181
9.3.Frequency Distribution 182
9.4.Probability Distribution 185
9.5.Parameters of Distribution 186
9.6.Probability Distribution Functions 190
9.7.Flood Frequency Analysis 196
9.8.Correlation and Regression Analysis 200
9.9.Hydrologic Processes 204
Examples 208
References 221
Index 223
