Irrigation Control Structures

  •  These are structures which are constructed in order to control and regulate discharges, depths, velocities, etc . in canals.
  •  They are very important to ensure the efficient functioning and safety of an irrigation canal system by giving  proper control upon the canals.
  •  Functions of canal regulation structures include:

o   to dissipate excess energy,

o   to measure discharge for proper distribution,

o   - for safety purpose, e.g. to cut off supplies to off take channel, remove silt and excess water,

o   to  raise  or lower the water surface in the channel

o   to cross obstacles such as drainage lines and depressions .

  •  Important Canal regulation structures:

ü  Canal Falls ( Drop Structures)

ü  Canal regulators ( Head regulator and cross regulator) or Checks permanent or temporary)

ü  Cross-Drainage works

ü  Canal Escapes

ü  Metering flumes,

ü  Canal Outlets, etc.

1. Drop Structures/Canal Falls

Canal Falls (Drop Structures) are canal control structures constructed at suitable intervals in a canal whenever the available natural ground slope is steeper than the designed bed slope of the canal. 

Functions of drop structures:

§  To reduce the velocity of flow and thus dissipate surplus energy

§  May also be equipped with a calibrated weir section which can be used to measure the quantity of water flowing over them.


2. Head and Cross Regulators

ü  Head regulator is constructed at the head of the off taking channel (or distributary) to control and regulate supplies entering the off taking channel.

ü  Thus, functions of head regulator are

o   to regulate or control supplies into off taking channel from the parent channel.

o   to cut off supplies when not needed in the off taking channel or when the off taking channel is  required to be closed for repairs.

o   to control silt entry into the off taking  channel

o   it serves as meter for measurement of discharge entering the off taking channel

A cross regulator is generally constructed across a parent channel for raising (to head) up the water level in the parent channel when  its discharge is less than the full supply discharge.

Therefore, functions of a across regulator are:

  •   to effect equitable distribution of supplies amongst the distributing channels
  •   to raise water level when supply in the parent channel is low to feed off takes
  •   to provide means for cutting off supplies for repairs, etc.
  •   to provide means of communication across the channels through the bridges/platform provided over them.
  •   they help to absorb fluctuations in the various sections of the canal system , and thus to prevent possibilities of breaches in the tail reaches.
  •   to help escape excess water from the canal in conjunction with escapes
  •   to control water surface slope in conjunction with falls for bringing the canals to regime slope and section.



3. Canal Outlets/Turnout structures

  • Canal outlets are small structures built on the bank of a distributary channel through which water is supplied to a water course (or a field channel).

4. Metering flume

  • is an artificially flumed (narrowed) section of the channel , which can be utilized for measuring the discharge in the channel.

5. Sediment Control devices

  • Are structures constructed in the canal to minimize problem of sedimentations.  
  • Sediment extractors (ejectors) are constructed in the main canals.



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