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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