---
title: "Discharge of Nakhu Khola from current meter data"
subject: "Engineering Hydrology"
chapter: 4
key: "semester_5/engineering_hydrology:current-meter-nakhu-khola"
source: https://www.bctengineer.com/q/semester_5/engineering_hydrology/current-meter-nakhu-khola
site: BCT Engineering
---

# Discharge of Nakhu Khola from current meter data

Engineering Hydrology · Chapter 4: Surface Runoff

- Asked in: 2082 Baisakh, 6 marks
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/engineering_hydrology/current-meter-nakhu-khola
- Whole chapter: https://www.bctengineer.com/md/semester_5/engineering_hydrology/chapter-4

## Question

Discharge measured at Nakhu Khola using current meter has the following data. Calculate the total discharge of river.

| Distance from left bank (m) | Depth (m) | Velocity at 0.2d (m/s) | Velocity at 0.8d (m/s) |
|---|---|---|---|
| 0 | - | - | - |
| 1.5 | 1.3 | 0.6 | 0.4 |
| 3.0 | 2.5 | 0.9 | 0.6 |
| 5.0 | 1.7 | 0.7 | 0.5 |
| 6.0 | 1.0 | 0.6 | 0.4 |
| 7.5 | 0.4 | 0.4 | 0.3 |
| 9.0 | - | - | - |

## Short answer

Mean velocity at each vertical was (v0.2 + v0.8)/2. Using mid-section method, segment discharge v_mean·depth·width summed to Q ≈ 6.62 m^3/s.

## Answer

**Mid-section method.** Two velocities are given at each vertical, so the mean velocity is
$$
v_m=\frac{v_{0.2}+v_{0.8}}{2},\qquad q_i=v_m\,d\,\frac{b_{i+1}-b_{i-1}}{2}
$$
The two banks (0 m and 9 m) have zero depth.

| x (m) | d (m) | $v_{0.2}$ | $v_{0.8}$ | $v_m$ (m/s) | w (m) | Area (m$^2$) | q (m$^3$/s) |
|---|---|---|---|---|---|---|---|
| 1.5 | 1.3 | 0.6 | 0.4 | 0.500 | 1.5 | 1.950 | 0.975 |
| 3 | 2.5 | 0.9 | 0.6 | 0.750 | 1.75 | 4.375 | 3.281 |
| 5 | 1.7 | 0.7 | 0.5 | 0.600 | 1.5 | 2.550 | 1.530 |
| 6 | 1 | 0.6 | 0.4 | 0.500 | 1.25 | 1.250 | 0.625 |
| 7.5 | 0.4 | 0.4 | 0.3 | 0.350 | 1.5 | 0.600 | 0.210 |
| **Total** | | | | | | **10.725** | **6.621** |

Mean velocity $= 0.617$ m/s.

**Answer: Total discharge $Q \approx 6.62\ \text{m}^3/\text{s}$.**

## Check yourself

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

1. How is mean velocity with 0.2d and 0.8d readings found?
   A. vm = (v0.2 + v0.8)/2
   B. vm = v0.2 x v0.8
   C. vm = v0.8 only
   D. vm = v0.2 + v0.8
   Answer: A. The average of readings at 0.2 d and 0.8 d represents the vertical. (Key point: Mean velocity)

2. What is the width for the vertical at 3.0 m (neighbours at 1.5 and 5.0)?
   A. 3.5 m
   B. 1.75 m
   C. 1.5 m
   D. 2.5 m
   Answer: B. (5.0 - 1.5)/2 = 1.75 m. (Key point: Strip width)

3. What is the total discharge?
   A. About 10.7 m^3/s
   B. About 0.617 m^3/s
   C. About 6.62 m^3/s
   D. About 3.28 m^3/s
   Answer: C. The sum of vm x w x d is 6.621 m^3/s (area 10.725 m^2). (Key point: Result)

## Related in Engineering Hydrology

- [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
- [Discharge of Jhiku khola from stream gauging data](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Acurrent-meter-jhiku-khola) — Engineering Hydrology, chapter 4
- [River discharge with current meter constants a and b](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Acurrent-meter-a0-51-b0-03) — Engineering Hydrology, chapter 4
- [Discharge from current meter at 0.6 depth](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Acurrent-meter-0-32n-0-032) — Engineering Hydrology, chapter 4
- [Discharge from multi-point current meter data](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Acurrent-meter-two-point-0-3n) — Engineering Hydrology, chapter 4
- [Mid-section method discharge from current meter data](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Amidsection-0-3n-0-004) — Engineering Hydrology, chapter 4

## Related in other subjects

- [Discharge from 0.2d and 0.8d velocities (left bank)](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Astream-gauging-left-bank) — Hydro Power, chapter 2
- [Discharge from 0.2d and 0.8d velocities (right bank)](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Astream-gauging-right-bank) — Hydro Power, chapter 2
- [Discharge from depth and mean velocity data](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Adischarge-depth-mean-velocity) — Hydro Power, chapter 2
- [Stream discharge from current meter revolutions (V = 0.51N + 0.03)](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Astream-gauging-revolutions-0-51) — Hydro Power, chapter 2, asked 2×