Soil and water conservation in semi-arid areas

by Norman W. Hudson Silsoe Associates Ampthill, Bedford United Kingdom

    Soil Resources, Management and Conservation Service

FAO Land and Water Development Division

Food and Agriculture Organization of the United Nations Rome, 1987

TABLE OF CONTENTS

FOREWORD

ACKNOWLEDGEMENTS

SUMMARY

LIST OF PLATES

LIST OF FIGURES

LIST OF TABLES

l.INTRODUCTION

1.1THE SCOPE OF THIS BULLETIN

1.2 THE IMPORTANCE OF THE SEMI-ARID REGIONS

1.3 DROUGHT AND CHANGE

1.4 POLITICAL AND SOCIAL CHANGE

2. THE PROBLEM OF AGRICULTURE IN THE SEMI-ARID REGIONS

2.1 SOME GENERAL PROBLEMS

2.1.1 The Extent of Erosion

2.1.2 Differences Between Semi-arid Regions

2.1.3 Shortage of Information

2.1.4 Lack of Technology

2.2 PRESSURES

2.3 CLIMATE

2.3.1 Rainfall

2.3.2 Temperature and Wind

2.4 SOIL

2.5 THE FARMING BACKGROUND

3.ASSESSING THE POSSIBILITIES FOR IMPROVING AGRICULTURE

3.1 PHYSICAL POTENTIAL

3.2 SOCIAL POSSIBILITIES

4. SOIL CONSERVATION

4.1 PRINCIPLES

4.1.1 The Extent of Erosion

4.1.2 Soil Conservation and Water Conservation

4.1.3 Integrated Programmes

4.1.4 Design Requirements

4.1.5 Relevant Technology

4.2 BIOLOGICAL SOIL CONSERVATION

4.2.1 Conservation Tillage

4.2.2 Deep Tillage

4.2.3 Conservation Farming

4.2.4 Improved Water Use Efficiency

4.3 MECHANICAL CONSERVATION WORKS

4.3.1 Principles

4.3.2 Terracing

4.3.3 Water Disposal

4.3.4 Low-cost Measures

5. WATER CONSERVATION

5.1 PRINCIPLES

5.1.1 Choice of Method

5.1.2 Some Design Principles

5.1.3 The Effect of Scale

5.2 METHODS FOR CROP LAND

5.2.1 Broad Bed and Furrow System (BBF)

5.2.2 Ridging and Tied Ridging

5.2.3 Conservation Bench Terraces (CBT) (also known as Zingg terrace, and flat channel terrace)

5.2.4 Contour furrows (also known as contour bunds and desert strip farming)

5.3 WATER SPREADING (THE USE OF RUN-ON AREAS)

5.3.1 Natural Run-off

5.3.2 Collected and Diverted Run-off

5.3.3 Inundation Methods

5.3.4 Flood Diversion

5.4 SURFACE DRAINAGE

5.5 OTHER SOURCES OF WATER: SNOW, DEW AND MIST

5.5.1 Snow Management

5.5.2 Dew and Mist

6. WATER HARVESTING AND USE

6.1 HARVESTING METHODS

6.2 TREATMENT OF CATCHMENTS

6.2.1 Natural Catchments and Minor Changes

6.2.2 Shaping Catchments

6.2.3 Chemical Treatments

6.2.4 Waterproof Membranes

6.3 WATER STORAGE

6.3.1 Small Earth Dams

6.3.2 Small Weirs

6.3.3 Sand Dams

6.3.4 Off-stream Storage

6.3.5 Storage below Ground Level

6.4 LOSSES OF STORED WATER

6.4.1 Seepage Losses

6.4.2 Evaporation Losses

6.5 DEVELOPING GROUNDWATER

6.5.1 Groundwater Recharge

6.5.2 Groundwater Extraction

7. APPLICATIONS OF WATER CONSERVATION

7.1 GRAZING LAND

7.1.1 The Issues

7.1.2 Management of Grazing Areas

7.1.3 Reclamation of Degraded Range Land

7.2 TREES AND SHRUBS

7.2.1 The Issues

7.2.2 Methods and Techniques

7.2.3 Agroforestry

REFERENCES

ANNEX 1: GLOSSARY OF LOCAL NAMES

ANNEX 2: Summary of FAO-UNESCO system of soil classification