---
title: "Methods of presenting rainfall data"
subject: "Engineering Hydrology"
chapter: 2
key: "semester_5/engineering_hydrology:rainfall-data-presentation-methods"
source: https://www.bctengineer.com/q/semester_5/engineering_hydrology/rainfall-data-presentation-methods
site: BCT Engineering
---

# Methods of presenting rainfall data

Engineering Hydrology · Chapter 2: Precipitation

- Asked in: 2081 Baisakh, 4 marks
- Video: [Understanding Mass Curve of Rainfall and Hyetograph | Presentation of Rainfall data](https://www.youtube.com/watch?v=EaTQ4n98x_M) — IntuitiveLearn
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/engineering_hydrology/rainfall-data-presentation-methods
- Whole chapter: https://www.bctengineer.com/md/semester_5/engineering_hydrology/chapter-2

## Question

What are the different methods for the presentation of rainfall data? Explain any two methods.

## Short answer

Rainfall data are presented as tables, hyetographs, mass curves, IDF curves, DAD curves, isohyetal maps. Hyetograph is a bar chart of intensity vs time showing storm pattern; mass curve plots cumulative rain vs time, slope gives intensity, used to find maximum depths and derive hyetograph.

## Answer

Rainfall data can be presented in the following ways:

1. **Tables** of hourly, daily, monthly and annual rainfall.
2. **Hyetograph** (bar chart of depth or intensity vs time).
3. **Mass curve** (cumulative rainfall vs time).
4. **Intensity-duration and IDF curves.**
5. **Depth-area-duration (DAD) curves.**
6. **Isohyetal maps** (contours of equal rainfall).
7. **Frequency curves and annual/monthly bar graphs.**

#### Two methods explained

**1. Hyetograph**
A hyetograph is a bar chart of rainfall depth (or intensity) in successive equal time intervals, plotted against time. It is obtained from the mass curve by taking the difference between successive ordinates.

```text
 mm/h
  |      ##
  |   ## ## ##
  | ## ## ## ## ##
  +------------------ time
```

It shows the storm pattern, the time of peak intensity and the total depth (area under the bars). It is the input for rainfall-runoff analysis such as the unit hydrograph.

**2. Mass curve of rainfall**
A mass curve plots the accumulated rainfall (y-axis) against time (x-axis) from the start of the storm. It is always rising or flat.

```text
 cm
  |        _____
  |      /
  |    /      <- steep = high intensity
  |__/
  +------------------ time
```

- The slope at any point gives the rainfall intensity.
- A horizontal portion means no rain.
- It is used to find the maximum depth for a duration, to derive the hyetograph, and to prepare intensity-duration curves.

## Check yourself

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

1. How is a hyetograph obtained from the mass curve?
   A. Sum of ordinates
   B. Slope at origin
   C. Area under curve
   D. Differences of successive ordinates
   Answer: D. Bars of depth in equal intervals. (Key point: Hyetograph derivation)

2. What does the slope of a mass curve give?
   A. Rainfall intensity
   B. Total depth
   C. Return period
   D. Area
   Answer: A. Steep means high intensity. (Key point: Mass curve slope)

3. What does a horizontal part of the mass curve mean?
   A. Heavy rain
   B. No rain
   C. Gauge fault
   D. Maximum intensity
   Answer: B. Cumulative depth does not increase. (Key point: Flat portion)

## Related in Engineering Hydrology

- [Presentation of precipitation data, IDF curve](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Apresent-precip-data-idf) — Engineering Hydrology, chapter 2
- [Thiessen average rainfall, four gauges at rectangle corners](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Athiessen-rectangle-four-gauges) — Engineering Hydrology, chapter 2
- [Average rainfall by isohyetal method, Bagmati basin](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Aisohyetal-bagmati-442) — Engineering Hydrology, chapter 2
- [Maximum rainfall intensity for 1, 3, 5 hr](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Amax-intensity-1-3-5hr-7am) — Engineering Hydrology, chapter 2
- [Infiltration index from 8-hr rainfall, Bagmati Basin](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Aphi-index-bagmati-11-6cm) — Engineering Hydrology, chapter 3
- [River discharge from two-point current meter data](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Acurrent-meter-0-02ns) — Engineering Hydrology, chapter 4

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