Components of canal irrigation system

A canal irrigation system takes water from a river (or reservoir) and carries it by a network of canals to the fields.

 River --> HEADWORKS (weir/barrage + head regulator)
              |
         MAIN CANAL ---> escape (to river)
         /     |    \
   Branch   Branch   Branch      (cross regulator at each take-off)
      |
  Distributary ---- Distributary
      |
   Minor ---- Minor
      |
   OUTLET (module)
      |
   Watercourse (field channel) --> FIELD

Components

1. Headworks: diversion weir/barrage, under-sluices, divide wall, head regulator, fish ladder and silt excluder. They raise the water level and divert flow to the canal.
2. Main canal: the largest canal, carrying the whole supply, with a gentle slope; usually not used for direct irrigation.
3. Branch canals: take off from the main canal; carry 5-15 cumec or more.
4. Distributaries and minors: carry water to the field from the branch; minors are the smallest in the series.
5. Watercourses/field channels: carry water from the outlet to the fields (maintained by the farmers).
6. Regulating structures: head regulator, cross regulator, distributary head regulator, escape, outlets/modules.
7. Falls (drops) and cross-drainage works: reduce bed slope on steep ground, and carry the canal across streams (aqueduct, siphon, level crossing).
8. Other structures: bridges, escapes, measuring flumes, canal roads, and drains.

Main and branch canals are carrier canals; distributaries, minors and watercourses are distribution canals.