---
title: "RoR plant layouts; storage over RoR"
subject: "Hydropower Engineering"
chapter: 2
key: "semester_7/hydropower_engineering:ror-layouts-storage-importance"
source: https://www.bctengineer.com/q/semester_7/hydropower_engineering/ror-layouts-storage-importance
site: BCT Engineering
---

# RoR plant layouts; storage over RoR

Hydropower Engineering · Chapter 2: Planning of Hydropower Projects

- Asked in: 2075 Ashwin, 3+3 marks
- Video: [Chpt5 Run of River types Hydropower Projects- Hydropower Engineering #dipakdahal #engineering](https://www.youtube.com/watch?v=kb7qKIEibcw) — 𝐄𝐫. 𝐃𝐢𝐩𝐚𝐤 𝐃𝐚𝐡𝐚𝐥
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/hydropower_engineering/ror-layouts-storage-importance
- Whole chapter: https://www.bctengineer.com/md/semester_7/hydropower_engineering/chapter-2

## Question

Sketch and explain layouts of the run-of-river plant. Also explain the importance of storage hydropower plants over run-of-river plants.

## Short answer

RoR layout: weir, intake, desander, headrace (free-flow canal or pressure tunnel), forebay/surge tank, penstock, powerhouse, tailrace. Free-flow canal suits gentle slopes; pressure tunnel for steep terrain. Storage plants provide firm winter power, regulate flow, support peak demand, allow multipurpose use, and reduce spill and imports, unlike RoR's seasonality.

## Answer

#### Layouts of a run-of-river plant
A RoR plant has: a diversion weir/barrage, intake, gravel trap, settling basin (desander), headrace (canal or tunnel), forebay or surge tank, penstock, powerhouse and tailrace. Two common layouts:

**(a) With a free-flow headrace canal**
```text
 Plan
                          Forebay
 Weir/Intake--Desander--=========+
 ~~~~ River ~~~~~~~~~~~~~~~~~     | Penstock
                                  v
                            Powerhouse-->Tailrace-->River
```
**(b) With a pressure tunnel**
```text
 Section
 Weir   Intake   Headrace tunnel (pressure)
 ___|~~~|======================+ Surge tank
                               | Penstock
                               PH  --> Tailrace
```
- In (a), water flows with a free surface in the canal at a gentle slope, then drops in a penstock from the forebay. It is cheap in gentle terrain.
- In (b), water flows under pressure through a tunnel, suitable in steep, rocky or landslide-prone terrain. It needs a surge tank.

#### Importance of storage over RoR plants
- Gives **firm power** in the dry season, while RoR depends on river flow.
- Regulates flow, so it **increases installed capacity and energy** and the plant factor.
- Can supply **peak load** and respond to demand and the grid.
- **Multipurpose:** flood control, irrigation, water supply, fishing, tourism.
- Reduces the need for imports of power in the dry season.
- Less spill of the monsoon surplus.
- But it needs high capital, a long time, and resettlement/environment issues.

## Check yourself

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

1. Which RoR layout needs a surge tank?
   A. None
   B. Pressure tunnel
   C. Open channel
   D. Free-flow canal
   Answer: B. Pressure tunnels need surge tanks. (Key point: Surge tank)

2. Where is the free-flow canal layout suitable?
   A. Seabed
   B. Gentle terrain
   C. Only underground
   D. Steep landslide terrain
   Answer: B. Cheap in gentle terrain. (Key point: Canal suitability)

3. Why does storage give firm power?
   A. It uses fuel
   B. It regulates flow so dry-season supply is available
   C. No reason
   D. Depends on river flow
   Answer: B. Stored monsoon water is released later. (Key point: Firm power)

4. What are the limits of storage plants?
   A. Cheap and fast
   B. High capital, long time, resettlement
   C. Lower capacity
   D. No environmental effects
   Answer: B. Cost, time and resettlement. (Key point: Limits)

## Related in Hydropower Engineering

- [Three alternative RoR layouts](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-three-alternative-layouts) — Hydropower Engineering, chapter 2
- [RoR at 40% exceedence; storage regulation](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-40-percent-exceedence-storage-regulation) — Hydropower Engineering, chapter 3
- [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
- [Intakes for storage plants](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Astorage-plant-intake-types-arrangement) — Hydropower Engineering, chapter 4, asked 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
- [Optimizing plant capacity of a RoR project](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-optimum-capacity-discussion) — Hydropower Engineering, chapter 3

## 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
- [Components of a run-of-river plant](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aror-components-functions) — Power Plant Design, chapter 3, asked 2×
- [Daily pondage run-of-river components](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Adaily-pondage-ror-components) — Power Plant Design, chapter 3
- [Intake site selection for RoR plant](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aintake-site-selection-ror) — Hydro Power, chapter 5