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Drainage Principles and Applications





ILRI Publication16

Second Edition Completely Revised)

Drainage Principles andApplications

H .P. Rit zema Editor-in-Chief)

International Institute for Land Reclamation and Improvement,

P.O. Box 45,6700 AA Wageningen, The Netherlands, 1994



The first edition of this publication was issued in a four-volume series, with

the first volume appearing in 1972 and the following three volumes appearing

in 1973 and 1974. The second edition has now been completely revised and is

published in one volume.

The aims of ILRI are:

To collect information on land reclamation and improvement from all over

To disseminate this knowledge through publications, courses, and

To contribute -by supplementary research owards a better understanding

the world;

consultancies;

of the land and water problems in developing countries.

n t e r n a t i o n a l I n s t i tu t e for Land Rec lamat ion a nd Improvement / ILRI ,Wagen ingen , T he Ne the r lands .This book o r a n y part thereof may not be reproduced in an y form w i thou t th e wr i t t en pe rmissionof ILRI.

I S BN 90 70754 3 39

Pr in ted in Th e N e t h e r l an d s



Preface

Thirty-three years ago, the first International Course on Land Drainage was held at

ILRI in Wageningen. Since then, almost 1000 participants from more than 100countries have attended the Course, which provides three months of post-graduatetraining for professionals engaged in drainage planning, design, and management,and in drainage-related research and training. In the years of its existence, the Course

has proved to be the cornerstone of ILRI’s efforts to contribute to the development

of human resources.

From the beginning, notes of the Course lectures were given to the participants to

lend support to the spoken word. Some twenty-five years ago, ILRI decided to publish

a selection of these lecture notes to make them available to a wider audience.

Accordingly, in 1972, the first volume appeared under the title Drainage PrinciplesandApplications The second, third, and fourth volumes followed in the next two years,

forming, with Volume I, a set that comprises some 1200 pages. Since then, Drainage

Principles and Applications has become one of ILRI’s most popular publications, withsales to date of more than 8000copies worldwide.

In this third edition of the book, the text has been completely revised to bring it upto date with current developments in drainage and drainage technology. The authorsof the various chapters have used their lecture-room and field experience to adaptand restructure their material to reflect the changing circumstances in which drainage

is practised all over the world. Remarks and suggestions from Course participantshave been incorporated .into the new material. New figures and a new lay-out havebeen used to improve the presentation. In addition, ILRI received a vast measureof cooperation from other Dutch organizations, which kindly made their researchand field experts available to lecture in the Course alongside ILRI’s own lecturers.

To bring more consistency into the discussions of the different aspects of drainage,the four volumes have been consolidated into one large work of twenty-six chapters.The book now includes 550 figures, 140 tables, a list of symbols, a glossary, and anindex. It has new chapters on topical drainage issues e.g. environmental aspects of

drainage), drainage structures e.g. gravity outlets), and the use of statistical analysisfor drainage and drainage design. Current drainage practices are thoroughly reviewed,and an extensive bibliography is included. The emphasis of the whole lies uponproviding clear explanations of the underlying principles of land drainage, which,wisely applied, will facilitate the type of land use desired by society. Computerapplications in drainage, which are based on these principles, are treated at length

in other ILRI publications.



The revision of this book was not an easy job. Besides the authors, a large number

of ILRI’s staff gave much of their time and energy to complete the necessary work.

ILRI staff who contributed to the preparation of this third edition were:

Editorial Committee R. van Aart

M.G. Bos

H.M.H. Braun

K.J. LenselinkH.P. Ritzema

J.G. van Alphen

Th. M . Boers

R. Kruijne

N . A . de Riddert

G. Zijlstra

M.M. Naeff

Members prior to 1993

Language Editors M.F.L. Roche

Drawings J. van Dijk

Word Processing J.B.H. van DillenDesign and Layout J. van Dijk

J. van Manen

I want to thank everyone who was involved in the production of this book. It is my

belief that their combined efforts will contribute to a better, more sustainable, use

of the world’s precious land and water resources.

Wageningen, June 1994 M.J.H.P. Pinkers

Director

International Institute forLand Reclamation and Improvement/ILRI



Contents

Preface

1 Land Drainage: Why and How?M G Bos and T h M Boers

1.1

1.2

1.3

1.4

The Need for Land DrainageThe History of Land DrainageFrom the Art of Drainage to Engineering ScienceDesign Considerations for Land DrainageReferences

2 Groundwater InvestigationsN A de Ridder

2.1

2.2

2.3

2.4

2.5

2.6

IntroductionLand Forms2.2.1 Alluvial Plains2.2.2 Coastal Plains2.2.3 Lake Plains2.2.4 ,Glacial PlainsDefinitions2.3.1 Basic Concepts2.3.2 Physical PropertiesCollectionof Groundwater Data2.4.1 Existing Wells2.4.2 Observation Wells and Piezometers2.4.3 Observation Network2.4.4 Measuring Water Levels2.4.5 Groundwater QualityProcessing the Groundwater Data

2.5.1 Groundwater Hydrographs2.5.2 Groundwater MapsInterpretation of Groundwater Data

2.6.1 Interpretation of Groundwater Hydrographs2.6.2 Interpretation of Groundwater MapsReferences

3 Soil ConditionsH M H Braun and R Kruijne

3.1 Introduction3.2 Soil Formation

3.2.1 Soil-Forming Factors3.2.2 Soil-Forming Processes

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3.3 Vertical an d Ho rizontal Differentiation3.3.1 Soil Ho rizons

3.3.2 T he Soil Profile

3.3.3 Hom ogeneity and Heterogeneity3.4 Soil Cha racteristics and Prope rties

3.4.1 Basic Soil Cha racteristics3.4.2 Soil Prope rties

3.5.1 Soil D at a Collection

3.5.2 Existing Soil Info rmation3.5.3 Inform ation to be Collected

3.5.4 Soil Survey an d M apping

3.6.1 Introduction3.6.2 The FA O- UN ES CO Classification System3.6.3 Th e US DA /SC S Classification System

3.6.4 Discussion3.6.5 Soil Classification and Dra inag eAgricultural Use and Problem Soils for Drainage

3.7.1 Introduction3.7.2 Discussion

References

3.5 Soil Surveys

3.6 Soil Classification

3.7

4 Estimating Peak Runoff Rate s

J Boonstra

4.1 Introduction4.2 Rainfall Phenom ena4.2.1 De pth-A rea Analysis of Rainfall

4.2.2 Frequency Analysis of Rainfa ll

4.3.1 Run off Cycle4.3.2 Runoff Hy drograp h

4.3.3 Direct Run off Hy drograp h

4.4.1 Derivation of Emp irical Relationships4.4.2 Factors Determining the Curve Nu m ber Value4.4.3 Estimating the Curve Nu mb er Value4.4.4 Estimating the D ep th of the Direct Run offEstimating the Time Distribution of the Direct Runoff R ate

4.5.1 Un it Hy drograp h Theory4.5.2 Parametric Un it Hy drograp h4.5.3 Estimating Peak Run off RatesSumm ary of the Calculation Procedu re

References

4.3 Runoff Phenom ena

4.4 Th e Curve Num ber Method

4.5

4.64.7 Concluding Rem arks

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Evapotranspiration

R A Feddes and K J Lenselink

5.1 Introduction

5.2 Concepts and Developments5.3 Measuring Evapotranspiration

5.3.15.3.2 Estimating Interception5.3.3 Estimating the Evaporative Dema nd

5.4.1 Air-Temperature and Radiation M ethods5.4.2 Air-Temperature and Day-Length Method

Evaporation from Open Water: the Penman M ethod

5.6.15.6.2

5.6.35.6.4 Limited Soil-Water Supply

5.7 Estimating Potential Evapo transpiration5.7.15.7.2 Com puting the Reference Evap otranspirationReferences

The Soil Water Balance Method

5.4 Empirical Estimating Methods

5.55.6 Evapotranspiration from Cropped Surfaces

W et Cr op s with Full Soil Cover

Dry C ro ps with Full Soil Cover :the Penman-Monteith ApproachPartial Soil Cover an d Full Water Supply

Reference Evapotran spiration an d Cr op Coefficients

6 Frequency and Regression Analysis

R J Oosterbaan

6.16.2

6.3

6.4

6.5

IntroductionFrequency Analysis6.2.1 Introduction6.2.2 Frequency Analysis by Intervals

6.2.36.2.46.2.5 Conf idence AnalysisFrequency-Duration Analysis

6.3.1 Introduction6.3.2 Du ration Analysis

6.3.3 Depth-Duration-Frequency RelationsTheoretical Frequency Distributions6.4.1 Introduction6.4.2 Principles of Distribution Fitting6.4.3 The No rm al Distribution6.4.4 The Gum bel Distribution

6.4.5 Th e Exponential Distribution6.4.6Regression Analysis6.5.1 Introduction

6.5.2 The Ratio M ethod

Frequency Analysis by Rank ing of Da ta

Recurrence Predictions and R eturn P eriods

A Comparison of the Distributions

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6.5.3 Regression of y upon x

6.5.4 Linear Two-way Regression

6.5.5 Segmented Linear Regression

6.6.16.6.2 Periodicity of Time Series

6.6.3 Extrapolation of Time Series

6.6.4 Missing and Incorrect Data

References

6.6 Screeningof Time Series

Time Stability versus Time Trend

7 Basics ofGroundwater Flow

M G Bos

7.1 Introduction

7.2 Groundwater and Watertable Defined

7.3 Physical Properties, Basic Laws

7.3.1 Mass Density of Water7.3.2 Viscosity of Water

7.3.37.3.4 The Energy of Water

7.3.5

7.4.1 General Formulation

7.4.2

7.4.3 Validity of Darcy’s Equation

Some Applications of Darcy’s Equation

7.5.1

7.5.27.6 Streamlines and Equipotential Lines

7.6.1 Streamlines

7.6.2 Equipotential Lines

7.6.3 Flow-Net Diagrams

7.6.4 Refraction of Streamlines

7.6.5 The Laplace Equation

7.7.1 Impervious Layers

7.7.2 Planes of Symmetry

7.7.3 Free Water Surface7.7.4

7.7.5 Seepage Surface

7.8.1 The Dupuit-Forchheimer Assumptions

7.8.27.8.37.8.4

References

Law of Conservation of Mass

Fresh-Water Head of Saline Groundwater

7.4 Darcy’s Equation

The K-Value in Darcy’s Equation

7.5Horizontal Flow through Layered Soil

Vertical Flow through Layered Soils

7.7 Boundary Conditions

Boundary Conditions for Water at Rest or for

Slowly-MovingWater

7.8 The Dupuit-Forchheimer Theory

Steady Flow above an Impervious Horizontal Boundary

Watertable subject to Recharge or Capillary Rise

Steady Flow towards a Well

7.9 The Relaxation Method

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8 Subsurface Flow to D rains

H P Ritzema

8.18.2

8.3

8.48.5

Introduction

Steady-State Equations

8.2.1 The Hooghoudt Equation

8.2.2 The Ernst Equation8.2.3 Discussion of Steady-State Equations8.2.4 Application of Steady-State EquationsUnsteady-State Equations8.3.1 The Glover-Dumm Equation

8.3.2 The De Zeeuw-Hellinga Equation

8.3.3 Discussion of Unsteady-State Equations8.3.4 Application of Unsteady-State EquationsComparison between Steady-State and Unsteady-State EquationsSpecial Drainage Situations

8.5.1 Drainage of Sloping Lands8.5.2

8.5.3 Interceptor Drainage8.5.4

References

Open Drains with Different Water Levels and of Different

Sizes

Drainage of Heavy Clay Soils

9 Seepage and Groundwater Flow

N A de Ridder and G Zijlstra

9.1

9.29.39.4

9.5

9.6

9.7

Introduction

Seepage from a River into a Semi-confined AquiferSemi-confined Aquifer with Two Different Watertables

Seepage through a Dam and under a Dike

9.4.1 Seepage through a Dam9.4.2 Seepage under a DikeUnsteady Seepage in an Unconfined Aquifer9.5. I

9.5.2Periodic Water-Level Fluctuations9.6.1 Harmonic Motion

9.6.29.6.3Seepage from Open Channels

9.7.1 Theoretical Models9.7.2 Analog Solutions9.7.3

References

After a Sudden Change in Canal Stage

After a Linear Change in Canal Stage

Tidal Wave Transmission in Unconfined AquifersTidal Wave Transmission in a Semi-confined Aquifer

Canals with a Resistance Layer at Their Perimeters

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10 Single-W ell and Aquifer Tests

J Boons tra and N A de Ridder

10.1

10.2

10.3

10.4

10.5

IntroductionPreparing for an Aquifer Test10.2.1 Site Selection

10.2.210.2.3 Placement of Observation Wells

10.2.4Performing an Aquifer Test10.3.1 Time10.3.2 Head10.3.3 Discharge10.3.4 Duration of the TestMethods of Analysis

10.4.1

10.4.210.4.3 Time-Recovery Analysis

10.4.410.4.5Concluding Remarks

10.5.110.5.210.5.310.5.4 Conclusions

References

Placement of the Pumped Well

Arrangement and Number of Observation Wells

Time-Drawdown Analysis of Unconfined Aquifers

Time-Drawdown Analysis of Semi-confined Aquifers

Distance-Drawdown Analysis of Unconfined AquifersDistance-Drawdown Analysis of Semi-confined Aquifers

Delayed-Yield Effect in Unconfined AquifersPartially-Penetrating Effect in Unconfined AquifersDeviations in Late-Time Drawdown Data

11 Water in the Unsaturated Zone

P abat and J Beekma

1 Introduction

11.2 Measuring Soil-Water Content11 . 3 Basic Concepts of Soil-Water Dynamics

11.3.1 Mechanical Concept11.3.2 Energy Concept11.3.3 Measuring Soil-Water Pressure Head11.3.4 Soil-Water Retention

11.3.5 Drainable PorosityUnsaturated Flow of Water11.4.1 Basic Relationships11.4.2 Steady-State Flow11.4.3 Unsteady-State Flow

11.5 Unsaturated Hydraulic Conductivity

11.5.1 Direct Methods11S.2 Indirect Estimating Techniques

11.6 Water Extraction by Plant Roots11.7 Preferential Flow

11.8 Simulation of Soil-Water Dynamics in Relation to Drainage

11.4

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11.8.1 Simulation Models

11.8.211.8.3 Model Data Input

11.8.4

References

Mathematical Models and Numerical Methods

Examples of Simulations for Drainage

12 Determining the Saturated Hydraulic Conductivity

R J Oosterbaan and H J Nuland

12.1 Introduction12.2 Definitions12.3 Variability of Hydraulic Conductivity

12.3.1 Introduction12.3.2 Variability Within Soil Layers12.3.3 Variability Between Soil Layers

12.3.4

12.3.512.3.6 GeomorphologyDrainage Conditions and Hydraulic Conductivity

12.4.1 Introduction12.4.2 Unconfined Aquifers12.4.3 Semi-confined Aquifers

Seasonal Variability and Time Trend

Soil Salinity, Sodicity, and Acidity

12.4

13

12.4.4 Land Slope12.4.5 Effective Soil DepthReview of the Methods of Determination12.5.1 Introduction

12.5.2 Correlation Methods12.5.3 Hydraulic Laboratory Methods12.5.4 Small-scale In-Situ Methods12.5.5 Large-Scale In-Situ MethodsExamples of Small-scale In-Situ Methods

12.6.1 The Auger-Hole Method12.6.2 Inversed Auger-Hole MethodExamples of Methods Using Parallel Drains

12.7.1 Introduction

12.7.2 Procedures of Analysis

12.7.312.7.4

12.7.5References

12.5

12.6

12.7

Drains with Entrance Resistance, Deep SoilDrains with Entrance Resistance, Shallow Soil

Ideal Drains, Medium Soil Depth

Land Subsidence

R J de Glopper and H P Ritzema

13.1 Introduction13.213.3 Compression and Consolidation

Subsidence in relation to Drainage

13.3.1 Intergranular Pressure

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13.3.2 Terzaghi’s Consolidation Theory

13.3.3

Shrinkage of Newly Reclaimed Soils

13.4.1 The Soil-Ripening Process

13.4.2

13.4.3

13.5.1

13.5.2

Subsidence in relation to Drainage Design and Implementation

References

Application of the Consolidation Equations

13.4

An Empirical Method to Estimate Shrinkage

A Numerical Method to Calculate Shrinkage

The Oxidation Process in Organic Soils

Empirical Methods for Organic Soils

13.5 Subsidence of Organic Soils

13.6

14 Influencesof Irrigation on Drainage

M G Bos and W Wolters

14.1 Introduction

14.214.3 Salinity

14.4

Where Water Leaves an Irrigation System

Water Balances and Irrigation Efficiencies

14.4.1 Irrigation Efficiencies

14.4.2 Conveyance and Distribution Efficiency

14.4.3 Field Application Efficiency

Combined Irrigation and Drainage Systems

References

14.5

15 Salinity Control

JW van Hoorn and J G van Alphen

15.1

15.2 Soil Salinity and Sodicity

Salinity in relation to Irrigation and Drainage

15.2.1

15.2.2 Exchangeable Sodium

15.2.315.2.4 Classification of Salt-Affected Soils

15.2.5

Salt Balance of the Rootzone

15.3.1

15.3.2 Salt Storage15.3.3

15.3.4 Example of Calculation

15.3.5

Salinization due to Capillary Rise

15.4.1 Capillary Rise

15.4.2 Fallow Period without Seepage

15.4.3

15.4.4 Depth of Watertable

Electrical Conductivity and Soil Water Extracts

Effect of Sodium on Soil Physical Behaviour

Crop Growth affected by Salinity and Sodicity

Salt Equilibrium and Leaching Requirement

The Salt Equilibrium and Storage Equations expressed

in terms of Electrical Conductivity

Effect of Slightly Soluble Salts on the Salt Balance

15.3

15.4

Seepage or a Highly Saline Subsoil

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15.5 Leaching Process in the Roo tzone 567

15.5.1. Th e Roo tzone regarded as a Four-Layere d Profile 567

15.5.2 The L eaching E fficiency Coefficient 569

15.5.3 Th e Leaching Efficiency Coefficient in a Four-L ayeredProfile 573

15.7 Sodium H azar d of Irrigation Water 580.

15.6 Long-Term Salinity Level and Percolation 575

15.7. No Precipitation of Calcium C arbo nate 580

15.7.2 Precipitation of Calcium C arbo nate 58015.7.3 Examp les of Irrigation Waters con taining Bicarbonate 58315.7.4 Leaching R equirement a nd Classification of Sodic W aters 584

15.8 Reclam ation of Salt-Affected Soils15.8.1 Gen eral Considerations for Reclamation15.8.2 Leaching Techniques

15.8.3 Leaching Equa tions15.8.4 Chemical Am endments

References

16 Analysis of Water Balances

N A de Ridder and J Boonstra

16.1 Introduction16.2 Equations for W ater Balances

16.2.1 Com ponents of W ater Balances

16.2.2

16.2.3

16.2.4 Grou ndw ater Balance16.2.5 Integrated W ater Balances

16.2.6 Practical Applications16.2.7

16.3 Numerical Grou ndw ater Models16.3.1 General16.3.2 Types of Models

16.4 Exam ples of Water Balance Analysis16.4.116.4.2

16.4.3

References

W ater Balance of the Unsaturated Zon eWater Balance at the Land Surface

Equ ations for Water a nd Salt Balances

Processing an d Interpretation of Basic D at aW ater Balance Analysis With Flow Nets

W ater Balance Analysis With Models16.5 Final Remarks

17 Agricultural Drainage Criteria

, R J Oosterbaan

17.1 Introduction17.2 Types and A pplications of Agricultural Drainage Systems

17.2.1 Definitions17.2.2 Classification

17.2.3 Applications

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17.3 Analysis of Agricultural Drainage Systems

17.3.1 Objectives and Effects17.3.217.3.317.3.417.3.5

17.3.617.3.7Effects of Field Drainage Systems on Agriculture17.4.117.4.2 Watertable and Crop Production17.4.3 Watertable and Soil Conditions

17.4.4 SummaryExamples of Agricultural Drainage Criteria

17.5.117.5.2

17.5.317.5.4References

Agricultural Criterion Factors and Object FunctionsWatertable Indices for Drainage DesignSteady-State Versus Unsteady-State Drainage EquationsCritical Duration, Storage Capacity, and Design Discharge

Irrigation, Soil Salinity, and Subsurface DrainageSummary: Formulation of Agricultural Drainage Criteria

Field Drainage Systems and Crop Production17.4

17.5Rain-Fed Lands in a Temperate Humid ZoneIrrigated Lands in Arid and Semi-Arid Regions

Irrigated Lands in Sub-Humid ZonesRain-Fed Lands in Tropical Humid Zones

18 Procedures in Drainage Surveys

R an Aart and J G van Alphen

18.1 Introduction18.2 The Reconnaissance Study

18.2.1 Basic Data Collection

18.2.2 Defining the Land-Drainage Problem18.2.3 Examples18.2.4 Institutional and Economic Aspects

18.3 The Feasibility Study18.3.1 Topography18.3.2 Drainage Criteria18.3.318.3.4 The Hydraulic Conductivity Map

18.3.5

18.3.6 Field-Drainage System in Sub-Areas

18.3.718.3.8 Institutional and Economic Aspects

Implementation and Operation of Drainage Systems18.5.1 Execution of Drainage Works

18.5.218.5.3 Monitoring and Evaluating Performance

References

The Observation Network and the Mapping Procedure

The Contour Map of the Impervious Base Layer

Climatological and Other Hydrological Data

18.4 The Post-Authorization Study18.5

Operation and Maintenance of Drainage Systems

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19 Drainage Canals and Related Structures

M G Bos

19.1 Introduction19.2 General Aspects of Lay-out

19.2.1 Sloping Lands

19.2.2 The Agricultural Area19.2.3 Drainage Outlet19.2.4 Locating the Canal19.2.5

19.3.1 Design Water Levels19.3.2 Design Discharge Capacity19.3.3

19.3.4

19.3.5

19.3.6 Canal Curvature19.3.7 Canal Profiles

19.4 Uniform Flow Calculations19.4.1

19.4.2 Manning’s Equation19.4.3 Manning’s Resistance Coefficient19.4.419.4.5 Channels with Compound Sections

19.5.1 Introduction

19.5.2 The Sediment Transport Approach19.5.3 The Allowable Velocity Approach19.6 Protection Against Scouring

19.6.1 Field of Application19.6.219.6.319.6.4 Fitting of Sieve Curves19.6.5 Filter Construction

19.7.1 Introduction19.7.2 Straight Drop19.7.3 Baffle Block Type Basin

19.7.4 Inclined Drop19.7.5 USBR Type I11 Basin

19.8.1 General19.8.2 Energy LossesReferences

Schematic Map of Canal Systems

19.3 Design Criteria

Influence of Storage on the Discharge CapacitySuitability of Soil Material in Designing Canals

Depth of the Canal Versus Width

State and Type of Flow

Influence of Maintenance on the n Value

19.5 Maximum Permissible Velocities

Determining Stone Size of Protective LiningFilter Material Placed Beneath Rip-Rap

19.7 Energy Dissipators

19.8 Culverts

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22.4.3 Partial Penetration

22.4.4 Semi-confined Aquifers

22.5.1 Design Considerations

22.5.2 Well-Field Design

22.5.3 Well Design

22.5.4 Design Optimization

22.6.1 Borehole

22.6.2 Pump and Engine

References

22.5 Design Procedure

22.6 Maintenance

23 Pumps and Pumping Stations

J Wijd ieks and M G Bos

23.1 General23.2 Pump Types

23.2.1 Archimedean Screw

23.2.2 Impeller Pumps

Affinity Laws of Impeller Pumps

23.4.1 Description and Occurrence

23.4.2Fitting the Pump to the System

23.5.1

23.5.223.5.3

23.6 Determining the Dimensions of the Pumping Station

23.6.1 General Design Rules

23.6.2 Sump Dimensions

23.6.3 Parallel Pumping

23.6.423.6.5

23.6.6 Trash Rack

23.6.7

References

23.323.4 Cavitation

Net Positive Suction Head (NPSH)

Energy Losses in the System

Fitting the System Losses to the Pump CharacteristicsPost-Adjustment of Pump and System

23.5

Pump Selection and Sump Design

Power to Drive a Pump

The Location of a Pumping Station

24 Gravity Outlet Structures

W S de Vries and E J Huyskens

24.1 Introduction

24.2 Boundary Conditions

24.2.1 Problem Description

24.2.2 Outer Water Levels

24.2.3 Salt Intrusion

24.2.4 Inner Water Levels

Design of Gravity Outlet Structures24.3.1

24.3Types of Gravity Outlet Structures

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965966

966970

976

978978

980982982

984984986986986987990

993

996

997998

1001

100110011001100310151019

10201020



24.3.2 Location of Outlet Structures24.3.3

24.3.4

24.3.5 Other Aspects

References

Discharge Capacities of Tidal Drainage OutletsDesign, Construction, Operation, and Maintenance

25 Environmental Aspects o f Drainage

H P Ritzema and H M H Braun

25.1 Introduction

25.2 Objectives of Drainage25.3 Environmental Impacts25.4 Side-Effects Inside the Project Area

25.4.1 Loss of Wetland

25.4.2 Change of the Habitat

25.4.3 Lower Watertable

25.4.4 Subsidence25.4.5 Salinization25.4.6 Acidification

25.4.7 Seepage25.4.8 Erosion25.4.9

25.4.10 Health25.5 Downstream Side-Effects

25.5.1 Disposal of Drainage Effluent25.5.2 Disposal Options

25.5.3 Excess Surface Water25.5.4 Seepage from Drainage Canals

Leaching of Nutrients, Pesticides, and Other Elements

25.6 Upstream Side-Effects25.7 Environmental Impact Assessment

References

26 Land Drainage :Bibliography and Information Retrieval

G. Naber

26.1 Introduction

26.2 Scientific Information

26.2.1 Structure

1027

1027

1037

1039

1040

1041

1041

1041

1042

1044

1044

1045

1046

10461048

1048

1049

1050

1050

1051

1053

1053

1055

10591059

10601060

1063

1067

1067

1067

106726.2.2 Regulatory Mechanisms that Control the Flow of Literature 1067

A Land Drainage Engineer as a User of Information 1068

26.3.1 The Dissemination of Information 1069

26.3.2 Retrieval of Information 1070

26.3.3 Document Delivery 1071

26.4 Information Sources on Land Drainage 1072

26.4.1 Tertiary Literature 1072

26.4.2 Abstract Journals 1072

26.4.3 Databases 1072

26.4.4 Hosts or Information Suppliers 1073

26.3



26.4.5 Journals26.4.6 Newsletters26.4.7 Books26.4.8 Institutions26.4.9 Drainage Bibliographies26.4.10 Multilingual Dictionaries26.4.1 1 Proceedingsof International Drainage Symposia26.4.12 Equipment Suppliers26.4.13 Teaching and Training FacilitiesList of Addresses

List of Abbreviations

List of Principal Symbols and Units

Glossary

Index

1073107510751084

10861086

1087108810881089

1090

1091

1095

1107



1 Land Drainage: W h y and How?M.G.BOS and Th.M.Boers

1.1 The Need for Land Drainage

Th e current world pop ulation is roughly estimated a t 5000 million, half of whom livein developing countries. The average annual growth rate in the world populationapproximates 2.6%. To produce food and fibre for this growing population, theproductivity of the currently cultivated area must be increased and more land must

be cultivated.Land drainage, or the combination of irrigation and land drainage, is one of the

most important input factors to maintain or to improve yields per unit of farmedland. Figure 1 1 illustrates the im pact of irrigation w ater management an d the controlof the w atertable.

INFUENCE INDICATION OF

the degree the use

of water of other

control inputs

experimental field

conditians

advanced

water

practices

fullcontrol

of water

supply and

drainage

watertable

control

drought

elimination

flood

prevention

rain fed

uncontrolled

flooding

optimum

use of

inputs

and

cultural

practices

increased

fertilizer;

improved

seed and

pest control

low

fertilizer

application

nil1

experimental

over 1O tonslha

4

/

India, Burma 1.7

I I I I I I I1 2 3 4 5 6 7

country wide attained yields

tons of paddy rice per ha harvested)

Figure 1.1 Influence of water control, improved management, and additional inputs on yields of paddy

rice FAO 1979)

International Institute for Land Reclamation and Improvement

23



To enlarge the currently cultivated area, more land must be reclaimed than the land

that is lost e.g. to urban development, roads, and land degradation). In some areas,however, land is a limiting resource. In other areas, agriculture cannot expand at the

cost of nature.

Land drainage, as a tool to manage groundwater levels, plays an important role in

maintaining and improving crop yields:It prevents a decrease in the productivity of arable land due to rising watertables

A large portion of the land that is currently not being cultivated has problems of

and the accumulation of salts in the rootzone;

waterlogging and salinity. Drainage is the only way to reclaim such land.

The definition of land drainage, as given in the constitution of the InternationalCommission on Irrigation and Drainage/ICID 1979), reads:

‘Land drainage is the removal of excess surface and subsurface water from theland to enhance crop growth, including the removal of soluble salts from thesoil.’

In this publication, we shall adopt the ICID definition because it is generally knownand is applicable all over the world. Drainage of agricultural land, as indicated above,is an effective method to maintain a sustainable agricultural system.

1.2 The History of Land Drainage

Records from the old Indus civilizations i.e. the Mohenjo-Daro and the Harappa)show that ‘around 2500 B.C. the Indus Valley was farmed. Using rainfall andfloodwater, the farmers there cultivated wheat, sesame, dates, and cotton. Surplusagricultural produce was traded for commodities imported from neighbouringcountries. Irrigation and drainage, occurring as natural processes, were in equilibrium:

when the Indus was in high stage, a narrow strip of land along the river was flooded;

at low stage, the excess water was drained Snelgrove 1967).

The situation as sketched for the Indus Valley also existed in other inhabited valleys,but a growing population brought the need for more food and fibre. Man increased

his agricultural area by constructing irrigation systems: in Mesopotamia c. 3000 B.C.

Jacobsen and Adams 1958), n China from 2627 B.C. King 1911, as quoted by Thorneand Peterson 1949), in Egypt c. 3000 B.C. Gulhati and Smith 1967), and, aroundthe beginning of our era, in North America, Japan, and Peru Kaneko 1975; Gulhatiand Smith 1967).

Although salinity problems may have contributed to the decline of old civilizationsMaierhofer 1962), there is evidence that, in irrigated agriculture, the importance of

land drainage and salinity control was understood very early. In Mesopotamia, controlof the watertable was based on avoiding an inefficient use of irrigation water andon the cropping practice of weed-fallow in alternate years. The deep-rooted cropsshoq and agul created a deep dry zone which prevented the rise of salts through

capillary action Jacobsen and Adams 1958). During the period from 1122 B.C. to

24



220 A.D. saline-alkali soils in the N or th China Plain an d in the W ei-Ho Plain wereameliorated with the use of a good irrigation and drainage system, by leaching, by

rice planting, and by silting from periodic floods (Wen and Lin 1964).

Th e oldest known polders and related structures were described by H om er in his Iliad

They w ere found in the Periegesis of Pausanias (Greece). His a ccount is as follows

(see Kn auss 1991 for details):

‘In my account of Orchomenos, I explained how the straight road runs at firstbesides the gully, and afterwards to the left of the flood water. On the plain ofthe Kaphyai has been made a dyke of earth, which prevents the water from theOrchomenian territory from doing harm to the tilled land of Kaphyai. Inside thedyke flows along another stream, in size big enough to be called a river, anddescending into a chasm of the earth it rises again (at a place outside the polder).’

In the second century B.C. the R om an C at0 referred t o the need to remove water

from wet fields (Weaver 1964), and there is detailed evidence tha t during the R om ancivilization subsurface drainage was also known. Lucius Inunius Moderatus

Columella, who lived in Rome in the first century, wrote twelve books entitled: ‘De

Re Rustica’ in which he described how land should be made suitable for agriculture(Vutik 1979) as follows:

‘ A swamp y soil mu st first of all be ma de free of excess water by me ans of a dra in,

which may be open o r closed. In com pac t soils, ditches are used; in lighter soils,ditches or closed drains which discharge into ditches. Ditches m ust have a sideslope, otherwise the walls will collapse. closed drain is ma de of a ditch ,

excavated t o a dep th of three feet, which is filled to a maximum of half this dep thwith stones o r gravel, clean from soil. T he ditch is closed by backfilling with soilto the surface. If these materials are not available, bushes may be used, coveredwith leaves from cypress or pine trees. Th e outlet of a closed dra in int o a ditchis made of a large stone on to p of two other stones.’

During the Middle Ages, in the countries around the North Sea, people began toreclaim swam ps an d lacustrine and maritime lowlands by draining the water throu gha system of ditches. Land reclamation by gravity drainage was also practised in theFa r East, for instance in Japan (Kaneko 1975). Th e use of the w indmill to p um p water

mad e it possible to turn deeper lakes into polders, for example the 7000-ha BeemsterPolder in The Ne therl and s in 1612 (Leeghwater 1641). Th e word polder, whichoriginates from the D utc h language, is used internationally to indicate ‘a low-lyingarea surrounded by a dike, in which the water level can be controlled independentlyof the ou tside water’.

During the 16th, 17th, and 18th centuries, drainage techniques spread over Europe,including Russia (Nosenko and Zonn 1976), and to the U .S .A . (Wooten and Jones1955). The invention o f the steam engine early in the 19th century brought aconsiderable increase in pumping capacity, enabling the reclamation of larger lakes

such as the 15 000-ha Haarlemm ermeer, southwest of Am sterdam , in 1852.

25



In the 17th century, the removal of excess water by closed drains, essentially the same

as described above by Columella, was introduced in England. In 18 O clay tiles startedto be used, and after 1830 concrete pipes made with portland cement Donnan 1976).The production of drain pipes was first mechanized in England and, from there, it

spread over Europe and to the U.S.A. in the mid-19th century Nosenko and Zonn1976). Excavating and trenching machines, driven by steam engines, made their advent

in 1890, followed in 1906 by the dragline in the U.S.A. Ogrosky and Mockus 1964).

The invention of the fuel engine in the 20th century has led to the development of

high-speed installation of subsurface drains with trenching or trenchless machines.

This development was accompanied by a change from clay tiles to thick-walled,

smooth, rigid plastic pipes in the 1940’s, followed by corrugated PVC and polyethylene

tubing in the 1960’s. Modern machinery regulates the depth of drains with a laser

beam.The high-speed installation of subsurface drains by modern specialized machines

is important in waterlogged areas, where the number of workable days is limited, and

in intensively irrigated areas, where fields are cropped throughout the year. In thiscontext, it is good to note that mechanically-installed subsurface drainage systemsare not necessarily better than older, but manually-installed systems. There are many

examples of old drains that still function satisfactorily, for example a 100-year-old

system draining 100 ha, which belongs to the Byelorussian Agricultural Academy inRussia Nosenko and Zonn 1976).

Since about 1960, the development of new drainage machinery was accompanied bythe development of new drain-envelope materials. In north-western Europe, organicfilters had been traditionally used. In The Netherlands, for example, pre-wrapped

coconut fibre was widely applied. This was later replaced by synthetic envelopes. Inthe western U.S.A., gravel is more readily available than in Europe, and is used as

drain-envelope material. Countries with arid and semi-arid climates similar to the

western U.S.A. e.g. Egypt and Iraq) initially followed the specifications for the designof gravel filters given by the U.S. Bureau of Reclamation/USBR 1978). The hightransport cost of gravel, however, guided designers to pre-wrapped pipes in countries

like Egypt Metzger et al. 1992), India Kumbhare et al. 1992), and PakistanHoneyfield and Sial 1992).

1.3 From the Art of Drainage to Engineering Science

As was illustrated in the historical sketch, land drainage was, for centuries, a practicebased on local experience, and gradually developed into an art with more generalapplicability. It was only after the experiments of Darcy in 1856 that theories were

developed which allowed land drainage to become an engineering science Russell

1934; Hooghoudt 1940; Ernst 1962; Kirkham 1972; Chapter 7). And although these

theories now form the basis of modern drainage systems, there has always remainedan element of art in land drainage. It is not possible to give beforehand a clear-cuttheoretical solution for each and every drainage problem: sound engineering

judgement on the spot is still needed, and will remain so.

26



The rapid development of theories from about 1955 to about 1975 is well illustrated

by two quotations from Van Schilfgaarde. In 1957 he wrote:‘Notwithstanding the great progress of recent years in the development ofdrainage theory, there still exists a pressing need for a more adequate analytical

solution to some of the most common problems confronting the design engineer.’

In 1978, the same author summarized the state of the ar t for the International DrainageWorkshop at Wageningen Van Schilfgaarde 1979) as:

‘Not much will be gained from the further refinement of existing drainage theoryor from the development of new solutions to abstractly posed problems. Thechallenge ahead is to imaginatively apply the existing catalogue of tricks to the

development of design procedures that are convenient and readily adapted bypractising engineers.’

With the increasing popularity of computers, many of these ‘tricks’ are combined in

simulation models and in design models like SWATRE Feddes et al. 1978; Feddeset al. 1993), SALTMOD Oosterbaan and Abu Senna 1990), DRAINMOD Skaggs1980),SGMP Boonstra and de Ridder 1981), and DrainCAD Liu et al. 1990). Thesemodels are powerful tools in evaluating the theoretical performance of alternative

drainage designs. Nowadays, however, performance is not only viewed from a crop-production perspective, but increasingly from an environmental perspective. Withinthe drained area, the environmental concern focuses on salinity and on the diversityof plant growth. Downstream of the drained area, environmental problems due to

the disposal of drainage effluent rapidly become a major issue.Currently, about 170 million ha are served by drainage and flood-control systems

Field 1990). In how far the actual performance of these systems can be forecast bythe above models, however, is largely unknown. There is a great need for field researchin this direction.

The purpose of this manual is, in accordance with the aims of ILRI, to contribute

to improving the quality of land drainage by providing drainage engineers with ‘tools’for the design and operation of land drainage systems.

1.4 Design Considerations for Land Drainage

In the ICID definition ofdrainage, ‘the removal of excess water’ indicates that land)

drainage is an action by man, who must know how much excess water should beremoved. Hence, when designing a system for a particular area Figure 1.2), thedrainage engineer must use certain criteria Chapter 17) to determine whether or notwater is in excess. A ground-)water balance of the area to be drained is the most

accurate tool to calculate the volume of water to be drained Chapter 16).Before the water balance of the area can be made, a number of surveys must be

undertaken, resulting in adequate hydrogeological, hydropedological, and topogra-

phicmaps Chapters 2,3, and 18, respectively). Further, all sub-)surface water inflows

and outflows must be measured or estimated Chapters 4 10, and 16). Precipitation

27





.......................................I

...................p

I

I...................1

I.......................................

.................... ........c

I

col lector........................................

I4...................,....................

.....................................I

.................... t--------...--------

I

I.................... 1...................

I

........

I drainage out letI a indra in +-oundary o f drained area

Figure 1.3 Schematic drainage system

The main drainage canal ii) is often a canalized stream which runs through the lowest

parts of the agricultural area. It discharges its water via a pumping station or a tidal

gate into a river, a lake, or the sea at a suitable outlet point i) Chapters 23 and24).

Main drainage canals collect water from two or more collector drains. Although

collector drains iii) preferably also run through local low spots, their spacing is ofteninfluenced by the optimum size and shape of the area drained by the selected field-drainage system. The layout of the collector drains, however, is still rather flexible

since the length of the field drains can be varied, and sub-collector drains can bedesigned Chapter 19). The length and spacing of the field or lateral drains iv) willbe as uniform as is applicable. Both collector and field drains can be open drainsor pipe drains. They are determined by a wide variety of factors such as topography,soil type, farm size, and the method of field drainage Chapters 2 0 , 2 and 22).

The three most common techniques used to drain excess water are: a) surface drainage,b) subsurface drainage, and c) tubewell drainage.a) Surface drainage can be described as ASAE 1979) ‘the removal of excess water

from the soil surface in time to prevent damage to crops and to keep water from

ponding on the soil surface, or, in surface drains that are crossed by farmequipment, without causing soil erosion’. Surface drainage is a suitable technique

where excess water from precipitation cannot infiltrate into the soil and move

through the soil to a drain, or cannot move freely over the soil surface to a natural)channel. This technique will be discussed in Chapter 20;

b) Subsurface drainage is the ‘removal of excess soil water in time to prevent damageto crops because of a high groundwater table’. Subsurface field drains can be eitheropen ditches or pipe drains. Pipe drains are installed underground at depths varyingfrom to 3 m. Excess groundwater enters the perforated field drain and flowsby gravity to the open or closed collector drain. The basics of groundwater flowwill be treated in Chapter 7, followed by a discussion of the flow to subsurface

29



drains in Chapter 8. The techniques of subsurface drainage will be dealt with in

Chapter 21.

c) Tubewell drainag e can be described a s the ‘control of a n existing or potential highgroundwater table or artesian groundwater condition’. Most tubewell drainage

installations consist of a group of wells spaced with sufficient overlap of theirindividual cones of depression to control the watertable at all points in the area.

Flow to pu mp ed wells, an d the e xtent of the cone of de pression, will be discussedin Chapter 10. The techniques of tubewell drainage systems will be treated inChapter 22.

When draining newly-reclaimed clay soils or peat soils, one has to estimate thesubsidence to be expected, because this will affect the design. This problem, which

can also occur in areas draine d by tubewells, is discussed in C ha pte r 13.

Regardless of the technique used to drain a particular area, it is obvious that itmu st fit the local need to remove excess water. N ow aday s the ‘need to rem ove excess

water’ is strongly influenced by a concern for the environment. The design and

ope ration of all draina ge systems must contribu te to the sustainability of agriculturein the drained area and must minimize the pollution of rivers and lakes from

agricultural return flow (Cha pter 25).

References

ASAE, Surface Drainage Committee 1979. Design and construction of surface drainage systems

on farms in humid areas. Engineering Practice EP 302.2, American Society of Agricultural

Engineers, Michigan, 9 p.

Boonstra, J. and N.A. de Ridder 1981. Numerical modelling of groundwater basins : a user-oriented

manual. ILRI Publicat ion 29, Wageningen. 226 p.

Donnan, W.W. 1976. An overview of drainage worldwide. In: Third National Drainage Symposium;

proceedings. ASAE Publ icat ion 1-77,St . Joseph, pp. 6-9.

Ernst, L.F. 1962. Grondwaterstromingen in de verzadigde zone en hun berekening bij aanwezigheid

van horizontale evenwijdige open leidingen. Verslagen Landbouwkundige Onderzoekingen

67-15. PUDOC, Wageningen, 189p.

Feddes, R.A., P.J. Kowalik and H. Zaradny 1978. Simulation of field water use and crop yield.

Simulation Monographs, PUDOC, Wageningen, 189 p.

Feddes, R.A., M. Menenti, P. Kabat and W.G.M. Bastiaansen 1993. Is large-scale modelling of

unsaturated flow with areal average evaporation and surface soil moisture as estimated from

remote sensing feasible? Jou rnal Hydrology 143, pp.125-152.

Field, W.P. 1990. World irriga tion. Irrigation and Drainage Systems, 4,2, pp. 91-107.

FAO 1979. The on-farm use of water. FAO Committee on Agricultu re, Rome, 22 p.Gulhati, N.D. and W.Ch. Smith 1967. Irrigated agricultu re : a historical review. In: R.M. Hagan,

H.R. Haise and T.W. Edminster (eds.), Irrigation of agri cultu ra l lands. Agronomy 11 American

Society of Agronomy, Madison. pp. 3-11.

Hooghoudt, S.B. 1940. Algemeene beschouwing van het probleem van de detailontwatering en de

infiltratie door middel van parallel loopende drains, greppels, slooten e n kanalen. Verslagen van

landbouwkundige onderzoekingen 46 (14) B, Algemeene Landsdrukkerij , ’s-Gravenhage,193 p.

Honeyfield, H.R. and B.A. Sial 1992. Envelope design for sub-surface drainage system for Fordwah

Eastern Sadiqia (South) Project. In: W.F. Vlotman, Proceedings 5th international drainage

workshop : subsurface drainage on problematic irrigated soils : sustainability and cost

effectiveness. International Waterlogging and Salinity Research Institute, Lahore, pp. 5.26-5.37

ICID 1979. Amendments to the constitution, Agenda of the International Council Meeting a t Rabat.

Internat ional Commission on Irrigation and Dra inage , Morocco. ICID, New Delhi, pp. A-156-163.

30





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