---
title: "Importance of canal lining"
subject: "Irrigation and Drainage Engineering"
chapter: 4
key: "semester_6/irrigation_and_drainage_engineering:canal-lining-importance"
source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/canal-lining-importance
site: BCT Engineering
---

# Importance of canal lining

Irrigation and Drainage Engineering · Chapter 4: Design of Canals

- Asked in: 2070 Chaitra (old course), 4 marks
- Video: [Canal Lining | Types of Canal Lining | Advantages | Lined & Unlined Canal | Silting | Shiwani Jha](https://www.youtube.com/watch?v=LeYr8Dnoqhc) — Shiwani Jha
- 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-lining-importance
- Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-4

## Question

Write down the importance of canal lining.

## Short answer

Lining reduces seepage loss and waterlogging, allows higher velocity and smaller section, cuts maintenance and weed growth, stabilizes alignment, and increases command. Savings in water and maintenance often outweigh lining cost.

## Answer

Canal lining is an impervious layer (concrete, brick, soil-cement, stone, plastic film) on the bed and sides of a canal. It is important because:

1. **Controls seepage loss.** Unlined canals can lose 20-40% of the water; lining saves most of it, so more land can be irrigated with the same supply.
2. **Prevents waterlogging.** Reduced seepage keeps the water table down in the command area and avoids salinity.
3. **Allows higher velocity.** The smooth boundary ($n \approx 0.014$-$0.016$) and non-erodible surface permit a larger velocity, so a smaller cross-section, less land acquisition and less earthwork for the same discharge.
4. **Reduces maintenance.** No scour of bed and banks, less silting, and little weed growth.
5. **Gives stable alignment.** Canals can be run through sandy, porous or steep ground and at higher embankments; breaches are fewer.
6. **Increases command and improves water control.** Higher discharge at the tail and quicker water delivery.
7. **Economic.** Savings in water, maintenance and drainage normally exceed the annual cost of the lining.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why does lining save water?
   A. It reduces evaporation only
   B. It forms an impervious layer cutting seepage that can reach 20-40% in unlined canals
   C. It increases the canal slope
   D. It raises the water table
   Answer: B. Lower seepage means more water reaches the fields. (Key point: Seepage)

2. How does lining help the command area?
   A. It adds seepage to recharge ground water
   B. It silts the land
   C. Less seepage keeps the water table down, avoiding waterlogging and salinity
   D. It removes the need for drainage entirely
   Answer: C. Reduced seepage prevents water table rise. (Key point: Waterlogging)

3. Why can a lined canal have a smaller section?
   A. Lining reduces the design discharge
   B. Lining lowers n to 0.03
   C. Lining makes the slope zero
   D. The smooth non-erodible boundary (n about 0.014-0.016) permits higher velocity
   Answer: D. Higher velocity needs less area for the same Q. (Key point: Velocity)

## Related in Irrigation and Drainage Engineering

- [Economic analysis of canal lining](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Acanal-lining-economic-analysis) — Irrigation and Drainage Engineering, chapter 4, asked 2×
- [Types of lining in irrigation canals](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Acanal-lining-types) — Irrigation and Drainage Engineering, chapter 4
- [Concrete-lined canal: Q 350](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Alined-canal-q350-slope-15000) — Irrigation and Drainage Engineering, chapter 4