---
title: "Short note: River intake"
subject: "Water Supply Engineering"
chapter: 5
key: "semester_5/water_supply_engineering:river-intake-note"
source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/river-intake-note
site: BCT Engineering
---

# Short note: River intake

Water Supply Engineering · Chapter 5: Intakes

- Asked in: 2066 Jestha (old course)
- Video: [Raw water intake in rivers](https://www.youtube.com/watch?v=_PGAa6hKLXc) — Sidney Seckler Ferreira Filho
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/river-intake-note
- Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-5

## Question

Write a short note on river intake.

## Short answer

A river intake draws water through ports at different levels fitted with screens, gates, an intake tower, and a pipe to the pump well or treatment plant. Types are wet and dry. Ports at two or three levels with low entrance velocity avoid silt, while coarse and fine screens keep out debris.

## Answer

A **river intake** is a structure built in a river (or on its bank) to draw water for a water supply scheme. It has ports at different levels, screens, gates or valves, an intake well or tower, and an intake pipe or conduit to the pump well or treatment plant.

```text
   Foot bridge
  =========|===========
           |   Intake tower
 HFL ~~~~~ |  [ ]  gate/valve
           | __|__ upper port
 NWL ~~~~~ |/  |  \  <-- screens
           |   |__ middle port
 LWL ~~~~~ |   |
           |___|__ lower port
  River bed ///|\\\
              \|/ intake pipe to
                   pump well/treatment
```

**Types**
- **Wet intake**: the tower is filled with water; valves are operated from the top.
- **Dry intake**: the tower is dry; water flows through ports to a separate sump and valves are operated in the dry chamber.

**Important features**
- Ports at two or three levels give the clearest water in any season; bell-mouth entries and low entrance velocity (0.15 to 0.3 m/s) avoid drawing silt and debris.
- Coarse (20 to 50 mm) and fine screens (6 to 12 mm) keep out floating matter and fish.
- The structure is placed in a straight or outer bend reach with a stable bank and enough depth, upstream of pollution sources, and is made safe against floods and scour.
- Protection works (pitching, groynes) and a foot bridge for access are provided.

**Maintenance**: regular raking and cleaning of screens, inspection of gates and valves, and flushing silt from the well and pipe.

## Check yourself

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

1. What entrance velocity is used?
   A. 1.5 to 3 m/s
   B. 0.15 to 0.3 m/s
   C. Zero
   D. 5 m/s
   Answer: B. Low velocity avoids drawing silt. (Key point: Features)

2. Which are the two types?
   A. Wet and dry
   B. Spring and well
   C. Open and closed
   D. Gravity and pumped
   Answer: A. Wet is filled with water, dry is not. (Key point: Types)

3. Which is routine maintenance?
   A. Chlorinating
   B. Adding alum
   C. Dredging city
   D. Raking screens, inspecting gates, flushing silt
   Answer: D. These keep the intake functioning. (Key point: Maintenance)

## Related in Water Supply Engineering

- [General river intake and site selection](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ageneral-river-intake) — Water Supply Engineering, chapter 5, asked 3×
- [Intake definition, components, river intake](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aintake-components-river) — Water Supply Engineering, chapter 5, asked 2×
- [Dry river intake with sketch](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Adry-river-intake) — Water Supply Engineering, chapter 5, asked 2×
- [Wet and dry river intake](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Awet-dry-river-intake) — Water Supply Engineering, chapter 5

## Related in other subjects

- [RoR headworks sketch; intake importance and location](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-headworks-arrangement-intake-location) — Hydropower Engineering, chapter 5
- [Design of orifice type intake](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aintake-orifice-design-5cumec) — Hydropower Engineering, chapter 5
- [Design of side intake with trashrack](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aintake-side-design-3315masl) — Hydropower Engineering, chapter 5