---
title: "Irrigation water requirement of rice"
subject: "Irrigation and Drainage Engineering"
chapter: 2
key: "semester_6/irrigation_and_drainage_engineering:rice-irrigation-requirement-definition"
source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/rice-irrigation-requirement-definition
site: BCT Engineering
---

# Irrigation water requirement of rice

Irrigation and Drainage Engineering · Chapter 2: Irrigation Water Requirements

- Asked in: 2074 Bhadra, 2 marks
- Video: [7. Water requirement of rice](https://www.youtube.com/watch?v=LqXbX91E2Ag) — Vaart Farms
- 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/rice-irrigation-requirement-definition
- Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-2

## Question

Define irrigation water requirement for rice crop.

## Answer

**Irrigation water requirement (IWR) of rice** is the depth of water that must be supplied by irrigation to rice fields during the crop period, after deducting the effective rainfall, to meet crop evapotranspiration, seepage and percolation, land preparation (puddling) and standing-water needs:

$$
\begin{aligned}
IWR = ET_c + S\&P + WL + LP - P_e
\end{aligned}
$$

It is expressed in mm per period, or as a flow rate (l/s/ha).

## Check yourself

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

1. Rice irrigation water requirement includes
   A. ET_c only
   B. ET_c, seepage and percolation, standing water, land preparation, less effective rainfall
   C. ET_c plus rainfall
   D. only puddling water
   Answer: B. IWR = ET_c + S&P + WL + LP - Pe. (Key point: IWR components)

2. Effective rainfall in the IWR equation is
   A. added
   B. multiplied
   C. deducted
   D. ignored
   Answer: C. Rain meets part of the demand. (Key point: Effective rainfall)

3. IWR can be expressed as
   A. ha/cumec only
   B. kg/ha
   C. mm/atm
   D. mm per period or l/s/ha
   Answer: D. Depth or flow rate per unit area. (Key point: Expression of IWR)

## Related in Irrigation and Drainage Engineering

- [Steps for rice irrigation requirement](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Arice-irrigation-requirement-steps) — Irrigation and Drainage Engineering, chapter 2, asked 4×
- [Steps of crop water requirement calculation](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Acrop-water-requirement-steps) — Irrigation and Drainage Engineering, chapter 2, asked 2×
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- [Crop coefficient curve for rice](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Acrop-coefficient-curve-rice) — Irrigation and Drainage Engineering, chapter 2
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