A blog for AGEN 506 Class 2015, Irrigation System Evaluation

AGEN 506: IRRIGATION WATER MANAGEMENT AND SYSTEM EVALUATION

CREDIT UNITS: 2

Year: 2014/2015 Season

Lecturer: Dr. M. K. Othman (Associate Professor of Irrigation Engineering)

Office: NAERLS, Block A, Room A209/Administration Block (Office of AD)
             Ahmadu Bello University, Zaria, Nigeria

COURSE OUTLINES & LECTURE NOTES

1)      Irrigation water management

a)      Basic water management concept

i)        Evapotranspiration

ii)      Irrigation schedule

iii)    Crop critical growth stages

iv)    Irrigation with water deficit

b)      System operation: Automated and manual

c)      System maintenance

2)      System evaluation

a)      Irrigation efficiencies and factors affecting them

b)      Measurements of irrigation efficiencies: Methods and devices

Introduction

All field crops need soil, water, air and light (sunshine) to grow. The soil gives stability to the plants; it also stores the water and nutrients which the plants can take up through their roots. The sunlight provides the energy which is necessary for plant growth. The air allows the plants to "breath". Without water crops cannot grow. Too much water is not good for many crops either. Apart from paddy rice, there are only very few crops which like to grow "with their feet in the water". The most well-known source of water for plant growth is rain water. There are two important questions which come to mind: What to do if there is too much rain water? What to do if there is too little rain water?

If there is too much rain, the soil will be full of water and there will not be enough air. Excess water must be removed. The removal of excess water - either from the ground surface or from the root zone - is called drainage. If there is too little rain, water must be supplied from other sources; irrigation is needed. The amount of irrigation water which is needed depends not only on the amount of water already available from rainfall, but also on the total amount of water needed by the various crops. Management of irrigation water involves application of the right amount of water needed by the crops at the right time using economical and efficient method.

There are two major factors which determine the amount of irrigation water to be applied:

1.   The total water need of the various crops

2.  The amount of rain water which is available to the crops

In other words: the irrigation water need or requirement is the difference between the total water need of the crops and the amount of rainfall which is available to the crops. Determination of the crop water need requires measurement and analysis of the crop and climatic data. The water need of a crop thus, consists of transpiration plus evaporation. Therefore, the crop water need is also called "evapotranspiration". 

Download full Lecture Note and presentation from the links below:

AGEN 506 Lecture note

AGEN 506 Presentation

[1] Prepared by M. K. Othman