---
title: "Irrigation, disadvantages, scope in Nepal"
subject: "Irrigation and Drainage Engineering"
chapter: 1
key: "semester_6/irrigation_and_drainage_engineering:define-irrigation-scope-nepal"
source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/define-irrigation-scope-nepal
site: BCT Engineering
---

# Irrigation, disadvantages, scope in Nepal

Irrigation and Drainage Engineering · Chapter 1: Introduction

- Asked in: 2076 Baisakh, 1+1+2 marks
- Video: [Module 1 Lecture 02 - Scope and Advantages/Disadvantages of Irrigation](https://www.youtube.com/watch?v=zzvUAAmKx1U) — Farhan Kazi
- 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/define-irrigation-scope-nepal
- Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-1

## Question

Define irrigation. What are the disadvantages of irrigation? Describe the scope of irrigation in Nepal.

## Short answer

Irrigation is the artificial application of water to land when rainfall is insufficient. Disadvantages include waterlogging, salinity, disease, high costs. In Nepal, about 2.6 million ha cultivable, half currently irrigated; large perennial rivers and groundwater in Terai, scope for small/lift/drip in hills, winter irrigation crucial.

## Answer

#### Irrigation
Irrigation is the artificial application of water to land to supply the moisture that crops need for growth when natural rainfall is insufficient.

#### Disadvantages of irrigation
- **Waterlogging** and a rising water table from over-irrigation and seepage.
- **Salinity and alkalinity** of the soil from salts left behind after evaporation.
- Mosquito breeding, so malaria and other water-related diseases may increase.
- High cost of construction and maintenance; possible displacement of people.
- A damp climate and cooler weather around large canals.
- Possible conflicts over water and loss of natural flow downstream.

#### Scope in Nepal
- Cultivable land is about 2.6 million ha, and a large part of it (especially in the Terai) can be irrigated, but only about half has irrigation, so there is wide scope for expansion.
- Rainfall is concentrated in the monsoon, so winter and spring irrigation is needed.
- Large perennial rivers (Koshi, Gandaki, Karnali, Mahakali) give abundant water for canals, and groundwater in the Terai is plentiful.
- The hills have scope for small, lift, drip and sprinkler irrigation.
- Irrigation raises food production and farmers' income and supports multipurpose development.

## Check yourself

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

1. Irrigation is best defined as:
   A. Natural rainfall on crops
   B. Draining excess water from land
   C. Artificial application of water to land to supply crop moisture when rainfall is insufficient
   D. Storing water in reservoirs only
   Answer: C. It supplements inadequate rainfall for crop growth. (Key point: Definition)

2. Which is a disadvantage caused by over-irrigation and seepage?
   A. Falling water table everywhere
   B. Increased soil nitrogen
   C. Reduced mosquitoes
   D. Waterlogging and a rising water table
   Answer: D. Excess water raises the water table; salts left by evaporation also cause salinity. (Key point: Waterlogging)

3. How does irrigation cause salinity?
   A. Salts are left in the soil after water evaporates
   B. Irrigation water adds nitrogen
   C. Salt is washed deep so soil becomes fertile
   D. Canals cool the air
   Answer: A. Evaporation leaves salts behind, particularly with poor drainage. (Key point: Salinity)

4. Why does Nepal have wide scope for irrigation expansion?
   A. All land is already irrigated
   B. Only about half of the cultivable land is irrigated, and rivers and Terai groundwater are plentiful
   C. There are no perennial rivers
   D. Rainfall is evenly distributed
   Answer: B. Unirrigated land, abundant water and concentrated monsoon rainfall give scope. (Key point: Scope in Nepal)

## Related in Irrigation and Drainage Engineering

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