---
title: "Methods of stream gauge reading"
subject: "Engineering Hydrology"
chapter: 4
key: "semester_5/engineering_hydrology:stream-gauge-reading-methods"
source: https://www.bctengineer.com/q/semester_5/engineering_hydrology/stream-gauge-reading-methods
site: BCT Engineering
---

# Methods of stream gauge reading

Engineering Hydrology · Chapter 4: Surface Runoff

- Asked in: 2072 Kartik, 6 marks
- Video: [Stream Gauging](https://www.youtube.com/watch?v=vVROw1GAT5c) — Aapka Engineer
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/engineering_hydrology/stream-gauge-reading-methods
- Whole chapter: https://www.bctengineer.com/md/semester_5/engineering_hydrology/chapter-4

## Question

Explain different methods of stream gauge reading with sketch.

## Short answer

Stage is measured manually with staff gauges (vertical/inclined), wire gauges, float-and-tape setups, and crest-stage gauges for peak flood. Automatic recording uses float-type stilling-well recorders, bubble/pressure gauges, pressure transducers, or ultrasonic/radar sensors, often telemetered.

## Answer

The **stage (gauge height)** of a river is the water-surface elevation above a datum. It is observed in the following ways.

#### 1. Non-recording (manual) gauges
**a) Staff gauge:** a graduated vertical enamelled plate (in cm), fixed on a pier, bridge abutment or wall. It is read by the observer 2 or 3 times a day. For wide stage ranges, **sectional staff gauges** are set in steps up the bank, or an **inclined gauge** is laid on the slope of the bank.

```text
   |  |  <- 3.0 m
   |  |
   |  |~~~~~ water level
   |  |  <- 2.0 m
   |__|
```

**b) Wire (chain) gauge:** a weighted chain or wire lowered from a fixed point on a bridge until it touches the water. The length of wire let out gives the stage below a known datum.

**c) Float and tape:** a float connected by a tape to a scale with counterweight.

**d) Crest-stage gauge:** a pipe containing cork powder or a similar substance that marks the maximum flood stage.

#### 2. Recording (automatic) gauges
**a) Float-type recorder:** a float in a stilling well (connected to the river by intake pipes) is attached to a counterweighted wire that turns a pulley and drives a pen on a clock-driven drum. It gives a continuous record (stage hydrograph).

```text
   recorder drum
      O--pen
      |  wire & counterweight
  ----|------- bridge/shelter
   |  |  |
   | [F]  |  <- float in stilling well
   |  ~~~~|~~ intake pipe
```

**b) Bubble (pressure) gauge:** gas is bubbled through a tube at the bed; the pressure needed is proportional to the water depth above the orifice.

**c) Pressure transducer / data logger:** a submerged sensor records pressure.

**d) Ultrasonic or radar gauge:** non-contact sensors measure the distance to the water surface.

Data may be sent by telemetry. Automatic gauges are used for floods and flood forecasting; staff gauges serve as the reference check.

## Check yourself

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

1. A staff gauge is
   A. A radar device
   B. An automatic pen recorder
   C. A pressure sensor
   D. A graduated vertical plate read by an observer
   Answer: D. It is a non-recording manual gauge fixed on a pier, wall or abutment. (Key point: Staff gauge)

2. In a float-type recorder, the stilling well is used to
   A. Damp waves so the float records the true water level
   B. Measure velocity
   C. Heat the float
   D. Store sediment
   Answer: A. It is connected to the river by intake pipes and gives a smooth, continuous stage record. (Key point: Stilling well)

3. In a bubble gauge, the gas pressure required is
   A. Proportional to velocity
   B. Proportional to water depth above the orifice
   C. Independent of depth
   D. Constant
   Answer: B. Pressure measures the depth above the orifice at the bed. (Key point: Bubble gauge)

## Related in Engineering Hydrology

- [Gauge-discharge relationship and discharge at 10.5 m](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Agauge-discharge-rating-7-5) — Engineering Hydrology, chapter 4
- [Slope-area discharge with three sections](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Aslope-area-3-section-260m) — Engineering Hydrology, chapter 4

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