--- title: "Components of canal irrigation system" subject: "Irrigation and Drainage Engineering" chapter: 3 key: "semester_6/irrigation_and_drainage_engineering:canal-components-sketch" source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/canal-components-sketch site: BCT Engineering --- # Components of canal irrigation system Irrigation and Drainage Engineering · Chapter 3: Canal Irrigation System - Asked in: 2079 Jestha, 4 marks; 2078 Baisakh, 4 marks; 2076 Bhadra, 5 marks; 2070 Bhadra, 5 marks; 2069 Bhadra, 5 marks; 2066 Bhadra (old course), 4 marks; 2072 Magh, 5 marks (asked 7 times) - Video: [What are components of irrigation canal|Purposes of different components of canal|Irrigation Channel](https://www.youtube.com/watch?v=kofomuZ3wEc) — Civillogy (Study of Civil Engineering) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/canal-components-sketch - Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-3 ## Question Explain with appropriate sketches the components of a canal irrigation system. ## Short answer A canal system comprises headworks (weir/barrage, head regulator) diverting river water into a main canal, which branches into distributaries and minors. Outlets supply watercourses to fields. Regulating structures (cross regulators, escapes) and cross-drainage works (aqueducts, siphons) are essential. ## Answer A canal irrigation system takes water from a river (or reservoir) and carries it by a network of canals to the fields. ```text 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. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is the main role of the headworks? A. Raise the water level and divert flow into the canal B. Distribute water to fields C. Carry water across streams D. Measure farm water use Answer: A. The weir/barrage and head regulator raise and divert river water. (Key point: Headworks) 2. Which canals are carrier canals in the answer? A. Distributaries and minors B. Main and branch canals C. Watercourses D. Outlets Answer: B. Main and branch canals carry water; distributaries, minors and watercourses distribute it. (Key point: Carrier vs distribution) 3. What is the role of the outlet and watercourse? A. They divert water from the river B. They carry the canal over a stream C. The outlet passes water from the minor/distributary to the watercourse that takes it to the field D. They drain excess water to the river Answer: C. Outlets (modules) control discharge into field channels maintained by farmers. (Key point: Outlet and watercourse) 4. Why are aqueducts, siphons and level crossings provided? A. To reduce silt in the canal B. To measure discharge C. To raise the water level at the head D. To carry the canal across natural streams Answer: D. They are cross-drainage works; falls reduce bed slope on steep ground. 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