WELCOME

Md. Nurul Kadir

Lecturer

Department of Agricultural Engineering

MAIN FEATURES

IRRIGATION EFFICIENCY

SIMPLE IRRIGATION CANAL DESIGN

IRRIGATION EFFICIENCY (Ei)

• The ratio between irrigation water actually utilized by growing crops and water diverted from a source (as a stream) in order to supply such irrigation water.

Usually expressed as a percentage

Different types of IRRIGATION EFFICIENCY

• Efficiency of water-conveyance (Ec)

• Efficiency of water-application (Ea)

• Efficiency of water-storage (Es)

• Efficiency of water use (Eu)

• Water distribution efficiency (Ed)

Different types of IRRIGATION EFFICIENCY

Efficiency of water-conveyance: Efficiency of water-

application:

Different types of IRRIGATION EFFICIENCY

Efficiency of water-storage:

Water distribution efficiency

Different types of IRRIGATION EFFICIENCY

Efficiency of water use

PROBLEM on IRRIGATION EFFICIENCY

A stream of 130 litres per second was diverted from a canal and 100 litres per

second were delivered to the field. An area of 1.6 ha was irrigated in 8 hours. The

effective depth of root zone was 1.7 m. the runoff loss in the field was 420 cu.m. The

depth of water penetration varied linearly from 1.7 m at the head end of the field to

1.1 m at the tail end. Available moisture holding capacity of the soil is 20 cm per

metre depth of soil. It is required to determine the water conveyance efficiency, water

application efficiency, water storage efficiency, and water distribution efficiency.

Irrigation was started at a moisture extraction level of 50% of the available moisture.

Reference: Irrigation Engineering and Hydraulic Structure by S. K. Garg. P-33

SIMPLE IRRIGATION CANAL DESIGN

OPEN CANALS

An open canal, channel, or ditch, is an open waterway whose purpose is to carry water from one place to another. Channels and canals refer to main waterways supplying water to one or more farms. Field ditches have smaller dimensions and convey water from the farm entrance to the irrigated fields.

According to the shape of their cross-section, canals are called rectangular (a), triangular

(b), trapezoidal (c), circular (d), parabolic (e), and irregular or natural (f)

SIMPLE IRRIGATION CANAL DESIGN

The most commonly used canal cross-section in irrigation and drainage, is the trapezoidal cross-section

The freeboard of the canal is the height of the bank above the highest water level anticipated. It is required to guard against overtopping by waves or unexpected rises in the water level.

SIMPLE IRRIGATION CANAL DESIGN

• The side slope of the canal is expressed as ratio,

namely the vertical distance or height to the horizontal

distance or width. For example, if the side slope of the

canal has a ratio of 1:2 (one to two), this means that the

horizontal distance (w) is two times the vertical distance

(h)

• A bottom slope of a canal