Effective rainfall in irrigated agriculture

Table of Contents

by N.G. Dastane
FAO Consultant

project coordinator Indian agricultural research institute New Delhi


The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

ISBN 92-5-100272-X

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© FAO 1978

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Table of Contents


Chapter I. Introduction

1. Effective rainfall and its significance
2. The pathway of rain water
3. Concepts of effective rainfall
4. Definition of effective rainfall
5. Effectiveness of rainfall
6. Factors influencing effective rainfall

Chapter II. Measurement of effective rainfall

1. Components of effective rainfall and their measurement

1.1 Rainfall and Irrigation
1.2 Surface Run-off
1.3 Rooting Depth
1.4 Deep Percolation Losses
1.5 Evapotranspiration

2. Empirical methods of determining effective rainfall

2.1 Soil Moisture Changes
2.2 Daily Soil Moisture Balance Method
2.3 Integrating Gauge
2.4 The Ramdas Method
2.5 Lysimeters
2.6 Drum Technique for Rice

3. Determining effective rainfall from formulae

3.1 Renfro Equation
3.2 U.S. Bureau of Reclamation Method
3.3 Potential Evapotranspiration/Precipitation Ratio Method (India)
3.4 USDA, SCS Method
3.5 Empirical Relationships

3.5.1 Crops other than rice
3.5.2 Rice Measurement in rice

4. Evaluation of methods

Chapter III. Application of effective rainfall data is irrigation and drainage projects

1. Irrigation project design
2. Irrigation project operation
3. Drainage projects

3.1 Drainage of Excess Water
3.2 Drainage for Leaching of Salts

4. Rice cultivation
5. The effect of groundwater
6. Effective rainfall in unirrigated and low rainfall, areas

Chapter IV. Increasing the proportion of effective rainfall its effectiveness and further lines of work

1. Increasing effective rainfall

1.1 Reducing Surface Run-off
1.2 Increasing Infiltration (except in rice culture)
1.3 Building Water Storage Structures
1.4 Minimizing Peep Percolation Losses

2. Increasing the effectiveness of rainfall
3. Further lines of work needed in the field of effective rainfall in agriculture

3.1 Collecting Data by Setting Up Crop Lysimeters
3.2 Verification of Empirical Methods
3.3 Development of Empirical Methods in Different Areas
3.4 Utilizing Information of Effective Rainfall in Agricultural Practices
3.5 Increasing Effective Rainfall Under Field Conditions
3.6 Increasing the Effectiveness of Rainfall