Modern Land Drainage: Planning, Design and Management of Agricultural Drainage Systems, 2nd Edition

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Cover Half Title Title Page Copyright Page Contents List of tables List of figures List of boxes Preface About the authors PART I Introduction 1 Land drainage for agriculture 1.1 Drainage objectives; Scope of the book 1.2 Global drainage zones 1.2.1 Temperate zone 1.2.2 Arid and semi-arid zone 1.2.3 Humid and semi-­humid zone 1.3 Agro-hydrological 1.4 Waterlogging control 1.4.1 Positive and adverse impacts 1.4.2 Responses to improved drainage 1.5 Salinity control 1.6 Drainage systems 1.7 Bio-drainage 1.8 Environmental impacts 1.8.1 Stream flow regimes 1.8.2 Water quality 1.8.3 Wetlands and conservation drainage 1.8.4 Public health 1.9 Drainage development considerations 2 Planning and design considerations 2.1 Design rainfall 2.2 Percolation of excess irrigation water 2.3 Design of field drainage systems 2.4 Determination of design criteria 3 Remote sensing and field reconnaissance 3.1 Need for drainage and problem diagnosis 3.2 Remote sensing and aerial survey 3.3 Field investigations 3.4 Planning stakeholder engagement 3.5 Stages of project preparation 3.6 Operation, management and maintenance 4 Assessment of costs 4.1 Required information 4.2 Discounting 4.3 Evaluation indices 4.4 Cost evaluation of open and pipe drainage systems incl. O&M 4.5 Cost calculations for pipe drainage systems 4.5.1 Cost structure for pipe drainage construction 4.5.2 Guidelines for cost calculations 4.5.3 Example cost calculation PART II Investigations 5 Climate, land, soil and environment 5.1 Climate 5.1.1 Climate; soil moisture balance calculations 5.1.2 Climate: rainfall depth­duration­frequency studies 5.2 Topography 5.3 Soil and land conditions 5.4 Soil parameters and properties 5.4.1 Texture 5.4.2 Plasticity index 5.4.3 Bulk density and soil moisture content 5.4.4 Sample quantity and density 5.4.5 Data requirement for drain envelope design 5.5 Watertable and groundwater 5.5.1 Watertable observation wells 5.5.2 Piezometric studies 5.5.3 Groundwater sampling 5.6 Hydrology and geohydrology 5.6.1 Runoff and flooding 5.6.2 Outlet conditions 5.6.3 Geohydrological conditions 5.7 Agriculture and irrigation 5.8 Pilot areas and field testing 5.8.1 Types of pilot areas 5.8.2 Analysis of results of pilot areas 5.8.3 Visual drainage need assessment 5.8.4 Statistical analysis 5.9 Environmental impact 5.9.1 Environmental impact assessment 5.9.2 Miscellaneous investigations 6 Water in the soil 6.1 Forms and nature of occurrence of water in the soil 6.2 Pressures in the soil water 6.3 Soil moisture characteristics 6.4 Soil water potential and soil water movement 6.5 Unsaturated zone; soil moisture constants 6.6 Infiltration and percolation 6.7 Groundwater flow; Laplace Equation 7 Hydraulic conductivity 7.1 Laboratory measurement 7.2 Field measurements below the watertable 7.2.1 Augerhole method 7.2.2 Piezometer method 7.2.3 Drain outflow method 7.3 Field measurements above the watertable 7.3.1 Infiltrometer-­method 7.3.2 Inverted augerhole method (Porchet method) 7.4 Composed K-­values 7.5 Surveys and data processing PART III Systems and technology 8 Subsurface drainage systems 8.1 Pipe drain systems 8.2 Deep ditch systems 8.3 Drainpipes 8.4 Envelopes 8.4.1 Envelope need 8.4.2 Material selection 8.4.3 Envelope thickness 8.5 Envelope design guidelines and criteria 8.5.1 Granular envelopes 8.5.2 Organic envelopes 8.5.3 Synthetic envelopes 8.6 Structures in pipe drain systems 8.6.1 Surface water inlets 8.6.2 Inspection, junctions and control 8.6.3 Crossings 8.6.4 Outlet of a pipe drain into a ditch or canal 8.6.5 Sump outlet 8.7 Construction of pipe drain systems 8.7.1 Setting out, depth and grade control 8.7.2 Installation methods and machinery 8.7.3 Construction and quality control 8.7.4 Timing of installation 8.7.5 Installation below the watertable 8.7.6 Backfill 9 Surface/shallow drainage systems 9.1 Bedding systems 9.2 Shallow ditch systems 9.2.1 Types of shallow ditch systems 9.2.2 Some technical aspects of shallow ditch systems 9.3 Mole drainage systems 9.4 Pipe drainage systems 9.5 Complementary measures 9.5.1 Sub-soiling 9.5.2 Deep ploughing 9.5.3 Chemical amendments and organic matter 9.5.4 Land levelling 10 Main drainage systems 10.1 Main features 10.1.1 Drainage basin (watershed, catchment) 10.1.2 Types and alignment of drainage canals 10.1.3 Outlet and water levels 10.1.4 Outlet structures 10.2 Lowland and upland drainage 10.2.1 Lowland polder 10.2.2 River polders 10.2.3 Upland discharges 10.2.4 Drainage of urban areas PART IV Design 11 Design of pipe drainage systems 11.1 Flow patterns 11.2 Drain spacing formulae 11.3 Hooghoudt formula 11.3.1 Use of the Hooghoudt formula 11.3.2 Notes on the Hooghoudt formula 11.3.3 Drain spacing determination in anisotropic soils 11.4 Non-steadystate drainage formulae 11.4.1 Falling watertable (Glover-Dummformula) 11.4.2 Fluctuating watertable (de Zeeuw and Hellinga formula) 11.5 Basic design criteria 11.5.1 Criteria for off-seasondrainage 11.5.2 Criteria for crop-seasondrainage 11.5.3 The impact of drain depth and drainable pore space 11.5.4 Drainage criteria determined by simulation 11.6 Drain depth 11.7 Pipe diameter 12 Design discharges 12.1 Discharge transformation 12.2 Design considerations 12.3 Statistical analysis of observed discharges 12.4 Flat basins 12.4.1 Subsurface drainage 12.4.2 Shallow drainage 12.4.3 Further guidance for flat basins 12.5 Sloping basins 12.5.1 Rational formula 12.5.2 Curve number method 12.5.3 Synthetic hydrographs 12.6 Area reduction formulae 12.7 Discharge reduction through storage 12.7.1 Retention reservoirs 12.7.2 Canal storage 13 Design of drainage canals, pumps and structures 13.1 Drainage canals 13.1.1 Discharge rate 13.1.2 Hydraulic gradient and water levels 13.1.3 Permissible flow velocities 13.1.4 Cross-section 13.1.5 Roughness coefficient 13.1.6 Freeboard 13.2 Structures in drainage canals 13.2.1 Culverts and bridges 13.2.2 Weirs 13.2.3 Backwater curves 13.2.4 Example canal design 13.3 Tidal outlets 13.3.1 Local variations in tide 13.3.2 Discharge through a sluice 13.3.3 Example of calculations 13.4 Pumps 13.4.1 Types of pumps 13.4.2 Pumping head and characteristics 13.4.3 Pump selection 13.4.4 Sump and intake design 13.4.5 Power and cost calculations 13.4.6 Example cost calculations of an electrically driven pump PART V Salinity control 14 Soil salinity 14.1 Forms of occurrence and distribution of salts in the soil 14.1.1 The soil solution 14.1.2 Adsorbed cations 14.1.3 Equilibrium relationships 14.1.4 Distribution of salts in the soil 14.2 Agricultural impacts; diagnosis and assessment 14.2.1 Osmotic problems 14.2.2 Toxicity problems 14.2.3 Dispersion problems 14.2.4 Corrosion problems 14.3 Classification 14.3.1 Classification systems 14.3.2 Field appearance 14.4 Conventional mapping and sampling 14.4.1 Sampling 14.4.2 Laboratory analysis 14.5 New salinity measurement and mapping techniques 14.5.1 The EM38 14.5.2 Time Domain Reflectometry 14.5.3 Remote Sensing methods 15 Irrigation induced salinisation 15.1 Salinisation by the applied irrigation water 15.2 Salinisation from the groundwater (capillary salinisation) 15.2.1 Critical watertable depth 15.2.2 Factors influencing capillary salinisation 15.3 Sodification 15.4 Salt balance of irrigated land 15.4.1 Leaching requirement calculations 15.4.2 Regional salt balances 15.5 Irrigation water quality 15.5.1 Salinity hazard 15.5.2 Sodicity hazard 15.5.3 Toxicity hazards 15.5.4 Examples of irrigation water quality appraisal 16 Drainage of irrigated land 16.1 Waterlogging and salinity 16.2 Surface drainage 16.3 Pipe drainage systems 16.3.1 Drain depth 16.3.2 Design criteria 16.3.3 Layout patterns 16.3.4 Pipe diameter 16.4 Well or vertical drainage 16.4.1 Types of aquifers 16.4.2 Design of well (vertical) drainage 16.5 Main drainage 16.5.1 Design discharge 16.5.2 Disposal of saline drainage water PART VI Special topics 17 Seepage and interception 17.1 Drainage systems for sloping land 17.1.1 Longitudinal drainage 17.1.2 Transverse drainage 17.2 Interception 17.2.1 Interception of seepage down the slope 17.2.2 Interception of canal seepage 17.3 Natural drainage of river valleys 17.4 Seepage into a polder 17.4.1 Semi-confinedflow 17.4.2 Phreatic flow 17.5 Seep zones and springs 18 Reclamation and drainage of unripened soils 18.1 The soil ripening processes 18.1.1 Physical ripening 18.1.2 Other ripening processes 18.2 Reclamation and drainage methods 18.2.1 Early reclamation stage 18.2.2 Development of the hydraulic conductivity (K-value) 18.2.3 Advanced reclamation stage 18.2.4 Drainage, evaporation and ripening 18.3 Acid sulphate soils 18.3.1 Acidification processes 18.3.2 Neutralisation and reclamation 18.3.3 Diagnosis 18.4 Subsidence prediction 18.4.1 Ripening subsidence 18.4.2 Settlement subsidence due to lowering of the watertable 18.4.3 Oxidation of peat soils 18.4.4 Experiences in the Netherlands 19 Drainage of rice lands 19.1 Surface drainage 19.2 Subsurface drainage 19.3 Crop diversification 19.4 Flood control 20 Controlled drainage 20.1 Issues and developments 20.2 Design considerations 20.2.1 Layout and technical provisions 20.2.2 Drain depth 20.2.3 Reuse arrangements 20.2.4 Discharge control and watertable management 20.3 Operation and maintenance by farmers 20.4 Controlled drainage at the regional level 21 Computer applications 21.1 Drainage design applications 21.1.1 Field systems 21.1.2 Canal systems 21.1.3 Preparation of drawings and documents 21.2 Rainfall discharge models 21.2.1 TR-20model 21.2.2 HEC-HMS 21.3 Ground water flow models 21.3.1 Spreadsheet models 21.3.2 MODFLOW and integrated programs 21.3.3 SGMP and SOURCE 21.4 Agrohydrological models 21.4.1 DRAINMOD version 6 21.4.2 SWAP 21.5 Salinity prediction models 21.5.1 SALTMOD 21.5.2 WATSUIT PART VII Management and New Developments 22 Research and innovation 22.1 Hydroluis pipe-envelopedrainage 22.2 Capiphon drain 22.3 Precision agriculture for water quality control 22.4 Bi-levelsubsurface drainage 23 Institutional, organisational and financial arrangements 23.1 Drainage laws 23.2 Development and management models 23.2.1 Public/private good model 23.2.2 Participatory development 23.2.3 Management Transfer 23.3 Public drainage organisation 23.4 Financing 23.4.1 Investments 23.4.2 Operation and maintenance costs 23.4.3 Fee systems 24 Maintenance 24.1 Classification 24.2 Organisation, planning and execution 24.3 Maintenance of open drainage canals 24.3.1 Problems 24.3.2 Requirements 24.3.3 Methods and equipment 24.3.4 Environmental considerations 24.4 Maintenance of pipe drains 24.4.1 Pipe cleaning 24.4.2 Entry of roots 24.4.3 Chemical clogging (iron ochre, gypsum) 24.4.4 Access facilities 24.4.5 Costs 24.5 Developing countries 25 Performance assessment and benchmarking 25.1 Drainage design and performance 25.2 Indicators 25.3 Performance assessment procedure 25.3.1 Preliminary investigations (first step) 25.3.2 Primary investigation (second step) 25.3.3 Cause analysis (third step) 25.4 Performance checking of pipe systems 25.5 Causes of under-performanceof drainage systems References and further reading Index