1. ce. irrigation engg. (1-5)
TRANSCRIPT
Comprehensive Theory
with Solved Examples and Practice Questions
IrrigationEngineering
Civil Engineering
Publications
MADE EASY Publications Pvt. Ltd.
Corporate Office: 44-A/4, Kalu Sarai (Near Hauz Khas Metro Station), New Delhi-110016E-mail: [email protected]: 011-45124660, 8860378007
Visit us at: www.madeeasypublications.org
Irrigation Engineering© Copyright by MADE EASY Publications Pvt. Ltd.All rights are reserved. No part of this publication may be reproduced, stored in or introduced into a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photo-copying, recording or otherwise), without the prior written permission of the above mentioned publisher of this book.
Edition: 2021
© All rights reserved by MADE EASY PUBLICATIONS Pvt. Ltd. No part of this book may be reproduced or utilized in any form without the written permission from the publisher.
Publications
Chapter 1Introduction to Irrigation,Methods of Irrigation ................................................11.1 Definition of Irrigation ...................................................................... 1
1.2 Main Concerns in Irrigation ............................................................ 1
1.3 Advantages of Irrigation .................................................................. 1
1.4 Disadvantages of Irrigation ............................................................ 2
1.5 Systems of Irrigation ......................................................................... 2
1.6 Surface and Sub Surface Irrigation .............................................. 2
1.6.1 Surface Irrigation ................................................................... 2
1.6.2 Subsurface Irrigation ............................................................ 3
1.7 Methods of Irrigation ....................................................................... 3
1.7.1 Uncontrolled Flooding........................................................ 4
1.7.2 Border Flooding ..................................................................... 4
1.7.3 Check Flooding ....................................................................... 5
1.7.4 Basin Flooding ........................................................................ 6
1.7.5 Furrow Method ....................................................................... 6
1.7.6 Subsurface Irrigation ............................................................ 6
1.7.7 Sprinkler Irrigation Method ............................................... 7
1.7.8 Drip Irrigation Method (Trickle irrigation) .................... 8
1.8 Irrigation Project Survey .................................................................. 9
1.9 Important Irrigation Projects in India ......................................... 9
Objective Brain Teasers ........................................................10
Conventional Practice Questions ......................................11
Chapter 2Water Logging, Quality of Irrigation Water ...............................122.1 Water Logging ...................................................................................12
2.2 Causes of Water Logging ...............................................................12
2.3 Effects of Water Logging................................................................12
2.4 Remedial Measures Adopted for
Controlling Water Logging ...........................................................12
(iii)
Irrigation EngineeringContents
2.5 Losses in Canal ..................................................................................13
2.6 Leaching ..............................................................................................13
2.6.1 Leaching Requirement of Soil .........................................14
2.7 Land Drainage ...................................................................................14
2.7.1 Surface Drainage ..................................................................14
2.7.2 Sub Surface Drainage ...........................................................15
2.7.3 Design and Maintenance of Open Drain .....................16
2.7.4 Relationship to Predict the Spacing between
Tile Drains if Discharge is Unknown ..............................17
2.8 Standard of Irrigation Water .........................................................19
Objective Brain Teasers ....................................................................21
Conventional Practice Questions ..................................................22
Chapter 3Water Requirement for Crops ......................233.1 Introduction .......................................................................................23
3.2 Cropping Seasons in India ............................................................23
3.2.1 Rabi ...........................................................................................23
3.2.2 Kharif ........................................................................................23
3.2.3 Zaid ...........................................................................................23
3.3 Duty and Delta ..................................................................................24
3.3.1 Duty ..........................................................................................24
3.3.2 Delta .........................................................................................24
3.4 Crop Period and Base Period ........................................................24
3.5 Relation between Duty and Delta ..............................................25
3.5.1 Derivation ...............................................................................25
3.6 Important Definition Linked with
Water Requirements of Crops ......................................................25
3.7 Brief Understanding ........................................................................27
3.8 Water Holding Capacity of the Soil ............................................27
3.9 Capillary Pores and Non-Capillary Pores .................................27
3.10 Classification of Soil Water ............................................................28
3.11 Soil Moisture Tension (SMT) .........................................................28
(iv)
3.12 Soil Moisture Stresses (SMS) .........................................................28
3.12.1 Osmotic Pressure .................................................................29
3.12.2 Leaching ..................................................................................29
3.13 Soil Moisture Constants ..................................................................29
3.14 Formula for Depth of Water Stored
in the Root Zone of the Soil ..........................................................30
3.15 Irrigation Efficiencies ......................................................................33
3.15.1 Various Types of Irrigation Efficiencies .........................34
3.16 Irrigation Requirements of Crops ...............................................35
3.16.1 Consumptive Irrigation Requirement (CIR) ................36
3.16.2 Net Irrigation Requirement (NIR) ...................................36
3.16.3 Field Irrigation Requirement (FIR) ..................................36
3.16.4 Gross Irrigation Requirement (GIR) ...............................36
3.17 Consumptive Use (Cu) or Evapotranspiration (ET) ..............38
3.17.1 Transpiration..........................................................................38
3.17.2 Evaporation ............................................................................38
3.17.3 Evapotranspiration (ET) .....................................................38
3.17.4 Factors Affecting Consumptive Use ..............................39
3.17.5 Potential Evapotranspiration (PET)
and Actual Evapotranspiration (AET) ...........................39
3.17.6 Some Important Definitions Linked with ET ..............40
3.17.7 Methods of Determining the
Consumptive Use of Water ...............................................40
Objective Brain Teasers ........................................................49
Conventional Practice Questions ......................................52
Chapter 4Canal Irrigation ..................................................544.1 Canal Irrigation .................................................................................54
4.2 Classification of Irrigation Canals ...............................................54
4.3 Canal Alignment ...............................................................................55
4.3.1 Ridge Canal ............................................................................55
4.3.2 Contour Canal .......................................................................55
4.3.3 Side Slope Canals .................................................................55
4.4 Warabandhi Method .......................................................................56
4.4.1 Primary and Secondary Distribution System .............57
4.5 Layout of an Irrigation Canal Network .....................................57
4.5.1 Main Canal ..............................................................................57
4.5.2 Branch Canal ..........................................................................58
4.5.3 Major Distributaries ............................................................58
4.5.4 Minor Distributaries ............................................................58
4.5.5 Water Courses (or field channels) ..................................58
4.6 Sediment Transport .........................................................................58
4.6.1 Important Points Linked with Sediment Transport .58
4.6.2 Suspended Load ..................................................................58
4.6.3 Mechanism of Sediment Transport ...............................59
4.7 Shield’s Entrainment Method for Design of
Non-scouring Stable Channels ....................................................60
4.7.1 Shield’s Expression ..............................................................60
4.7.2 Minimum Size of Bed Material that will
Remain in a Channel ...........................................................60
4.7.3 Strickler’s Formula ...............................................................60
4.8 Alluvial Channels and Non-Alluvial Channels ........................64
4.8.1 Alluvial Channels..................................................................64
4.8.2 Non-Alluvial Channels........................................................64
4.9 Design of Alluvial Channels in India ..........................................64
4.9.1 Regime Condition ................................................................64
4.10 Kennedy’s Theory .............................................................................64
4.10.1 Critical Velocity in a Channel ...........................................65
4.10.2 Design Procedure ................................................................65
4.10.3 Drawbacks ..............................................................................65
4.11 Lacey’s Regime Theory ...................................................................66
4.11.1 Lacey’s Regime Channels ..................................................66
4.11.2 Design Procedure ................................................................67
4.11.3 Drawbacks ..............................................................................67
4.12 Comparison of Lacey and Kennedy Theories .........................67
4.13 Lining of Canal ..................................................................................70
4.13.1 Necessity of Lining of Canal .............................................70
4.13.2 Advantages of Lining of Canal ........................................70
4.13.3 Disadvantages of Lining of Canal ..................................70
4.14 Types of Lining of Canal .................................................................71
4.15 Design of Lined Canal .....................................................................71
4.15.1 Procedure for Designing a Lined Channel ..................71
4.15.2 Indian Standard on Design of Lined Canals ...............72
4.16 Economics of Canal Lining ............................................................75
4.16.1 Assumption to be followed ..............................................75
(v)
4.16.2 Calculation of average annual benefits .......................75
4.16.3 Calculation of annual expense or cost .........................76
Objective Brain Teasers ........................................................78
Conventional Practice Questions ......................................82
Chapter 5Analysis of Gravity Dams ..................................845.1 Gravity Dams......................................................................................84
5.2 Forces Acting on a Gravity Dam.................................................84
5.2.1 External forces acting on a gravity dam ......................84
5.2.2 Combination of Loading for Design
(USBR Recommendation) .................................................90
5.3 Modes of Failure (Stability Requirements) ..............................90
5.4 Stability Analysis (Gravity method or 2D method) ..............93
5.5 Elementary Profile of a Gravity Dam .........................................95
Objective Brain Teasers ................................................................. 100
Conventional Practice Questions ............................................... 101
Chapter 6Theories of Seepage ........................................1046.1 Seepage Theories .................................................................................................104
6.1.1 Bligh’s Creep Theory ............................................................................104
6.1.2 Lane’s Weighted Creep Theory .....................................................105
6.1.3 Khosla’s Theory .......................................................................................105
6.1.4 Bligh’s Design Criteria .........................................................................107
Objective Brain Teasers ..................................................... 109
Conventional Practice Questions ................................... 110
Chapter 7Conveyance and RegulatingStructures for Canals .......................................1117.1 Cross Drainage Works .................................................................. 111
7.2 Types of CD Works ........................................................................ 112
7.3 Features of Design of CD Works ............................................... 115
7.4 Methods Used for Designing Channel Transition .............. 115
7.5 Introduction .................................................................................... 117
7.6 Canal Fall .......................................................................................... 117
7.6.1 Main Reason Behind the
Construction of a Canal Fall .......................................... 118
7.6.2 Factors Deciding Location of Falls .............................. 118
7.7 Types of Canal Falls ....................................................................... 118
7.7.1 Ogee Falls ............................................................................ 118
7.7.2 Rapid Falls ............................................................................ 118
7.7.3 Stepped Falls ...................................................................... 119
7.7.4 Notch Falls ........................................................................... 119
7.7.5 Vertical Drop Fall (Sarda Fall) ........................................ 120
7.7.6 Glacis Type Fall ................................................................... 120
7.8 Canal Regulators............................................................................ 121
7.8.1 Purpose of Providing a Canal Head Regulator ....... 121
7.8.2 Cross Regulator and Distributary
Head Regulators ................................................................ 122
7.9 Canal Escapes ................................................................................. 122
7.10 Types of Canal Escapes................................................................ 123
7.10.1 Based on Structural Design ........................................... 123
7.10.2 Based on the Purpose ..................................................... 124
7.11 Canal Outlets .................................................................................. 124
7.12 Types of Canal Outlets ................................................................. 124
7.13 Parameters for Studying the Behaviour of Outlets ........... 125
Objective Brain Teasers ................................................................. 128
Conventional Practice Questions ............................................... 130
Chapter 8River Training Works &Diversion Headworks ......................................1318.1 Behaviour of Rivers ..............................................................................................131
8.2 Classification of Rivers .......................................................................................131
8.2.1 Meandering river, Braided river and Deltaic rivers.............132
8.3 Meandering Phenomena and Meandering Parameter ................133
8.3.1 Meandering..............................................................................................133
8.3.2 Causes of Meandering .......................................................................133
8.3.3 Meander Parameters ..........................................................................134
8.3.4 Oxbow lake (or Cut off loop) ..........................................................134
8.4 River Training, Classification and Objectives ........................................135
8.4.1 Major objectives of river training works ..................................135
8.4.2 Classification of river training works ..........................................135
8.5 Methods of River Training ...............................................................................136
8.6 Introduction ............................................................................................................143
(vi)
8.6.1 Storage Headworks .............................................................................143
8.6.2 Diversion Headworks .........................................................................143
8.7 Location of Headworks .....................................................................................144
8.8 Components Parts of a Diversion Headworks ....................................144
8.8.1 Weir ...............................................................................................................144
8.8.2 Classification of Weir ...........................................................................145
8.8.3 Barrage ........................................................................................................146
8.8.4 Undersluices ............................................................................................147
8.8.5 Divide Wall .................................................................................................147
8.8.6 Fish Ladder ................................................................................................147
8.8.7 Silt Regulation Works ..........................................................................148
Objective Brain Teasers ..................................................... 150
Conventional Practice Questions ................................... 153
Chapter 9Dams Spillways and Energy Dissipaters .......1549.1 Dams and its Classification ........................................................ 154
9.1.1 Dams...................................................................................... 154
9.2 Selection of Site for Dam ............................................................ 155
9.2.1 Factors Governing Selection of Type of Dam ......... 155
9.2.2 Requirement of Good Site for
Construction of Dams ..................................................... 155
9.3 Spillways ........................................................................................... 155
9.3.1 Essential Requirement of Spillway.............................. 156
9.3.2 Types of Spillway ............................................................... 156
9.3.3 Components of Spillway ................................................ 160
9.4 Energy Dissipaters ........................................................................ 161
9.4.1 Hydraulic Jump Computations .................................... 161
9.4.2 Relationship between JHC and TWC ......................... 162
9.5 Types of Gates for Spillway Crests ........................................... 164
Objective Brain Teasers ..................................................... 166
Conventional Practice Questions ................................... 168
nnnn
