---
title: "Three alternative RoR layouts"
subject: "Hydropower Engineering"
chapter: 2
key: "semester_7/hydropower_engineering:ror-three-alternative-layouts"
source: https://www.bctengineer.com/q/semester_7/hydropower_engineering/ror-three-alternative-layouts
site: BCT Engineering
---

# Three alternative RoR layouts

Hydropower Engineering · Chapter 2: Planning of Hydropower Projects

- Asked in: 2069 Chaitra, 6 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/hydropower_engineering/ror-three-alternative-layouts
- Whole chapter: https://www.bctengineer.com/md/semester_7/hydropower_engineering/chapter-2

## Question

Prepare three alternative layout plans and sectional drawings of ROR hydropower plants.

## Short answer

Three RoR layouts: headrace canal with free surface flow for gentle valleys; pressure tunnel with surge tank for steep rocky terrain; dam-toe with short penstock for low-head rivers. All include intake, desander, waterway, penstock, powerhouse, chosen by topography, geology and cost.

## Answer

Three common RoR layouts are given with plan and section sketches.

#### Alternative 1: Headrace canal (free surface flow)
```text
Plan
 River ~~~~~\       Canal ___________
 Weir|Intake=Desander==============\ Forebay
                                    \ Penstock
                                     PH-->River
Section
 weir  canal (gentle slope)  forebay
 ____    _________________   |
     \__/                 \__| penstock
                              \_PH
```
Suitable for gentle valley slopes; low cost; open canal can be damaged by landslides.

#### Alternative 2: Headrace tunnel (pressure) with surge tank
```text
Plan
 Weir/Intake -> Desander -> Tunnel ==== Surge tank
                                          |
                                        Penstock
                                          |
                                          PH -> Tailrace
Section
 Intake======= tunnel =======(ST)
                              \ penstock
                               \_PH
```
Used for steep, rocky terrain and long bends; safe from landslide; high cost.

#### Alternative 3: Dam-toe/short penstock (low head)
```text
Plan
 ~~~ River ~~~~ Barrage + Powerhouse in line ~~~~
Section
  U/S  |barrage|  D/S
 ~~~~~~|  PH   |~~~~
       |intake |
```
Powerhouse is placed at the barrage; no canal or tunnel; for low-head, high-discharge rivers in the Terai.

In each layout, the intake, desander, headworks, waterway, powerhouse and tailrace are labelled, and the layout is chosen from topography, geology and cost.

## Check yourself

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

1. Which is a drawback of the open headrace canal?
   A. Very high cost
   B. Can be damaged by landslides
   C. Needs surge tank
   D. Needs no slope
   Answer: B. It suits gentle slopes only. (Key point: Canal layout)

2. When is a pressure tunnel layout used?
   A. Flat Terai
   B. Steep rocky terrain, safe from landslide
   C. Low cost sites
   D. No topography
   Answer: B. High cost but safe. (Key point: Tunnel layout)

3. Which layout has the powerhouse at the barrage with no canal or tunnel?
   A. Alternative 3 low-head
   B. None
   C. Alternative 1
   D. Alternative 2
   Answer: A. Used in Terai for low head, high discharge. (Key point: Dam-toe)

## Related in Hydropower Engineering

- [RoR plant layouts; storage over RoR](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-layouts-storage-importance) — Hydropower Engineering, chapter 2
- [Working principle of RoR, PRoR and ST plants](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-pror-storage-working-principle) — Hydropower Engineering, chapter 2
- [RoR layout: pressure tunnel and free surface](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-layout-pressure-tunnel-free-flow) — Hydropower Engineering, chapter 2
- [Development cycle; RoR layout with headrace canal](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Adev-cycle-ror-layout-headrace-canal) — Hydropower Engineering, chapter 2
- [Types of hydropower plants by head, turbine, load](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Ahydropower-plant-types-classification) — Hydropower Engineering, chapter 2
- [Importance of storage plants; pumped storage layout](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Astorage-importance-pump-storage-layout) — Hydropower Engineering, chapter 2

## Related in other subjects

- [ROR versus PROR hydropower plants](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aror-vs-pror) — Power Plant Design, chapter 3
- [Layout of hydropower scheme components](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Ahydropower-scheme-layout) — Hydro Power, chapter 5
- [Managing three hydropower project risks](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Arisk-manage-three-hydropower-risks) — Project Engineering, chapter 5
- [Combined plant layouts, performance and economics](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Acombined-layout-economics) — Power Plant Equipment, chapter 8