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Canal distribution system with sketch

Short answer

In the Terai, a gravity canal network diverts river water via a barrage into a main canal aligned along ridges. Branch canals, distributaries, and minors carry water to outlets, which supply field channels. Cross-drainage works and drains prevent flooding and waterlogging.

Describe with sketch the canal distribution system (suitable in the Terai region of Nepal).

In the Terai, the rivers bring water from the hills and the land has a gentle slope, so a gravity canal network is used. Water is diverted by a barrage or weir and carried in stages.

 River --[Barrage/Headworks]
             |
        MAIN CANAL
        /          \
   BRANCH CANAL    BRANCH CANAL
      |    \
 DISTRIBUTARY  DISTRIBUTARY
      |
    MINOR
      |
    OUTLET
      |
 WATERCOURSE / FIELD CHANNELS --> FIELDS
  • Main canal: takes off at the head regulator; aligned along the ridge (watershed) as far as possible.
  • Branch canals: take off from the main canal through branch head regulators (with a cross-regulator in the main canal just downstream to head up the water); they irrigate large blocks.
  • Distributaries and minors: carry about 0.25-3 cumec (minors less than about 0.25 cumec) and run along the minor ridges of the area.
  • Outlets: control the discharge into the watercourses; modules or pipe outlets are used.
  • Field channels: farmers' channels, supplied in turn by rotation (warabandi).
  • Drains and cross-drainage works (aqueducts, culverts) keep the system safe from floods and waterlogging.

Canals run along ridge lines (watershed alignment) so that the command is as large as possible.

✓ Answer checked by Claude Opus 5.5 (high effort)

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