Agricultural Drainage Water Management in Arid and Semi-Arid Areas


Rome, 2002

Table of Contents


Kenneth K. Tanji
Hydrology Program
Department of Land, Air and Water Resources
University of California
Davis, United States of America

Neeltje C. Kielen
Water Resources, Development and Management Service
FAO Land and Water Development Division

Reprinted 2003

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ISBN 92-5-104839-8

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© FAO 2002

Table of Contents



List of acronyms and symbols

Part I. Framework and technical guidelines

Chapter 1. Introduction

Need for drainage of irrigated lands
Need for water conservation and reuse
Towards drainage water management
Scope of this publication

Chapter 2. Defining the problem and seeking solutions

System approach in drainage water management
Defining the problem
Seeking solutions
Spatial issues
The use of models in recommending solutions and anticipated results

Model characteristics
Regional models

Rootzone hydrosalinity models

Principles of rootzone hydrosalinity models
Salt balance in the rootzone

Chapter 3. Framework for selecting, evaluating and assessing the impact of drainage water management measures

Definition of drainage water management and tasks involved
Driving forces behind drainage water management
Physical drainage water management options

Conservation measures
Reuse measures
Treatment measures
Disposal measures

Non-physical drainage water management options

Emission levels
Ambient levels
Salinity permits
Charges on inputs
Subsidies on practices
Charging/subsidizing outputs
Combined measures

Selection and evaluation of drainage water management options

Chapter 4. Water quality concerns in drainage water management

Drainage water quality
Factors affecting drainage water quality

Geology and hydrology
Cropping patterns
Use of agricultural inputs
Irrigation and drainage management
Drainage techniques and design

Characteristics of drainage water quality

Salts and major ions
Toxic trace elements

Water quality concerns for water uses

Crop production
Living aquatic resources, fisheries and aquaculture
Livestock production
Concerns for human health

Chapter 5. Water conservation

Need for water conservation measures
Hydrologic balance
Irrigation performance indicators
Source reduction through sound irrigation management

Reasonable losses
Management options for on-farm source reduction
Options for source reduction at scheme level
Impact of source reduction on long-term rootzone salinity
Maintaining a favourable salt balance under source reduction
Calculation example impact of source reduction on salinity of rootzone
Impact of source reduction on salt storage within the cropping season
Calculation example of impact of source reduction on salt balance of the rootzone
Impact of source reduction on salinity of drainage water
Calculation example of source reduction and the impact on drainage water generation and salinity

Shallow water table management

Controlled subsurface drainage
Considerations in shallow water table management
Capillary rise
Maintaining a favourable salt balance under shallow water table management
Calculation example of the impact of shallow water table management on salinity buildup and leaching requirement

Land retirement

Hydrologic, soil and biologic considerations
Selection of lands to retire
Management of retired lands

Chapter 6. Drainage water reuse

Relevant factors
Considerations on the extent of reuse
Maintaining favourable salt and ion balances and soil conditions

Maintaining a favourable salt balance
Maintaining favourable soil structure
Maintaining favourable levels of ions and trace elements

Reuse in conventional crop production

Direct use
Conjunctive use - blending
Conjunctive use - cyclic use

Crop substitution and reuse for irrigation of salt tolerant crops

Crop substitution
Reuse for irrigation of salt tolerant plants and halophytes

Reuse in IFDM systems
Reclamation of salt-affected land

Chapter 7. Drainage water disposal

Requirements for safe disposal
Disposal conditions
Disposal in freshwater bodies
Disposal into evaporation ponds

Evaporation ponds in Pakistan
Evaporation ponds in California, the United States of America
Evaporation ponds in Australia
Design considerations for evaporation ponds

Injection into deep aquifers

Chapter 8. Treatment of drainage effluent

Need for drainage water treatment
Treatment options

Trace element treatment

Flow-through artificial wetlands
Evaluation and selection of treatment options

Part II. Summaries of case studies from Central Asia, Egypt, India, Pakistan and the United States of America

Summaries of case studies

Drainage water management in the Aral sea basin
Drainage water reuse and disposal: a case study from the Nile Delta, Egypt
Drainage water reuse and disposal in northwest India
Drainage water reuse and disposal: a case study on Pakistan
Drainage water reuse and disposal: a case study on the western side of the San Joaquin Valley, California, the United States of America



Annex 1. Crop salt tolerance data

Annex 2. Water quality guidelines for livestock and poultry production for parameters of concern in agricultural drainage water

Annex 3. Drinking-water quality guidelines for parameters of concern in agricultural drainage water

Annex 4. Impact of irrigation and drainage management on water and salt balance in the absence of capillary rise

Annex 5. Capillary rise and data set for soil hydraulic functions

Annex 6. Trees and shrubs for saltland, salinity ratings and species lists

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