Technical Terms Used in Irrigation

Technical Terms Used in Irrigation

The various technical terms which are commonly used in irrigation are given below:

 Main Canal or Channels

The canal or channels which takes water directly from head works is called main canal.
Branch Canal or Channels: A canal or channels taking off from the main canal or channels or from some other branch canal or channel is called branch canal or channel.


The canal or channel taking water from the main or branch canal and distributing to minors and outlets is called distributary.

 Gross Commanded Area

It is the area enclosed inside an imaginary boundary line up to which certain irrigation canal or channel is capable of supplying water for irrigation purposes.

 Culturable Commanded Area

It is that area of land where crops can be grown satisfactorily.
Distribution System of Work: The network of canals starting from the source to the field for irrigation purposes is called distribution system of work.

Crop Ratio

It is the ratio of the area sunder the crops of two main seasons. Now suppose the area Rabi crop is 2000 hectares and the under Kharif crop it is 3000 hectares then crop ratio from Rabi to Kharif shall be 2 : 3.

Time Factor

It is the ratio between the number of days the canals has actually run to the number of days the canals was supposed to run for a particular period pf watering as per calculation and design.

Capacity Factor

It is the ratio between the average discharge of a canals or channels at a point and the full supply discharge of the canals or channels at the same point.

Head Water

The depth of water upstream from a structure or source of stream.

Available Head

It is the minimum difference between the supply and delivery water of levels available.


It is the total volume of water delivered to a crop divided by the area on which it is delivered. Thus amount of water depends upon the area under crop. It is measured in centimeters.


It is the degree of efficient utilization of irrigation water supplied from a canal to any crop, in other words it is the relation between the area irrigated and the quantity of water used. It is expressed in hectares per cubic meter per second.

Base Period

The time elapsed from the first watering at the time of sowing the crop to the last watering when he mature.

Cross Drainage Works

These are the engineering works constructed to cross the canals or channels to carry forward canal or channel safety. As the work constructed for the drainage it is called cross drainage works.
River Training Works: When the river is very wide and head works are to be constructed, some training is required to be done to the river in shape of guide banks, marginal banks and spurs. These training works are called river training works.

Head Works

The works constructed at the head of the canals or channels at the point of take off to divert the clear water in the canals or channels for purposes or irrigation.


The structures constructed for regulating the discharge in the canal or channels are called regulator.


It is the passage for the flow of surplus water or wastes in a weir or conduit.


It is a barrier constructed across the river. It is a small height wall of bricks, stone or concrete to raise the water level against its face to divert the river water to canal or channel. It is constructed at right angles to the flow of water.

Silt Load

The canals or channels which takes off from a river has to draw a fair share of silt flowing in the river. Also if the velocity of flow in the canals or channels is more than a certain non scouring velocity, some scouring takes place in the bed and sides of the canals or channels, the silt carried by the canals or channels flow is called the silt load.


It is a floor provided towards the down stream side of the weir in the canal or channel bed to prevent uplift of the canal. It also prevents the scouring of the floor. It may also be produced towards the upstream of the weir to act as impervious layer. when provided on both sides of the weir, it prevents the piping action of the weir.

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