---
title: "General requirements of functional RoR headworks"
subject: "Hydropower Engineering"
chapter: 5
key: "semester_7/hydropower_engineering:ror-headworks-requirements-only"
source: https://www.bctengineer.com/q/semester_7/hydropower_engineering/ror-headworks-requirements-only
site: BCT Engineering
---

# General requirements of functional RoR headworks

Hydropower Engineering · Chapter 5: Headworks of Run-of- River (RoR) Plants

- Asked in: 2070 Chaitra, 3 marks; 2071 Chaitra, 3 marks (asked 2 times)
- Video: [General Requirements of a Functional RoR Headworks 🌊🏭💡](https://www.youtube.com/watch?v=TI-zrwUx38I) — Hydropower
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/hydropower_engineering/ror-headworks-requirements-only
- Whole chapter: https://www.bctengineer.com/md/semester_7/hydropower_engineering/chapter-5

## Question

Explain the general requirements of a functional ROR headworks (what are the minimum performance standards of sound headworks?).

## Short answer

A sound RoR headworks must be stable against design floods, pass floods safely, deliver design discharge reliably, control sediment entry (high sill, undersluice, settling basin), exclude trash, have hydraulic efficiency, allow easy O&M, and meet environmental needs.

## Answer

A RoR headworks takes the design discharge from the river without storage, so it must work reliably in both floods and low flows. The minimum standards of a sound headworks are:

1. **Stable and safe structure**: designed for the 100-year flood (check for a higher flood); stable against sliding, overturning, uplift and piping; strong foundation with cut-offs and protection against scour.
2. **Adequate flood passage**: spillway, undersluice and gates must pass the design flood with an acceptable afflux, without overtopping the banks or the flood walls.
3. **Dependable water supply**: the intake must deliver the design discharge during the dry season, with the intake always submerged and no air entry or vortex; an environmental release is also kept in the river.
4. **Control of sediment**: bed load is excluded by a high-level intake sill, an undersluice, a gravel trap and river training works; suspended sediment above the design size is removed in the settling basin. The sediment must not accumulate in front of the intake.
5. **Control of floating debris and trash**: trash racks, trash booms, and a raking arrangement.
6. **Hydraulic efficiency**: small head loss in the intake, a smooth flow transition and a low-turbulence approach.
7. **Operation and maintenance**: gates and hoists easy to operate in floods, safe access, provision for flushing and inspection, and the arrangement for fish passage.
8. **Environment and economy**: minimum impact on the river and fish, and a low cost relative to the energy produced.

## Check yourself

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

1. Which combination keeps bed load out of a RoR headworks?
   A. Trash rack and boom
   B. High intake sill, undersluice, gravel trap and training works
   C. Fish ladder and stilling basin
   D. Large dead storage
   Answer: B. Bed load is excluded by these structures; the settling basin handles suspended sediment. (Key point: Sediment control)

2. What must the intake ensure to supply the design discharge in the dry season?
   A. It stays submerged with no air entry or vortex
   B. It is placed above the weir crest
   C. It has no gate
   D. It is as small as possible
   Answer: A. A submerged, vortex-free intake delivers the design discharge reliably. (Key point: Dependable supply)

3. Against which failures must the weir be stable?
   A. Cavitation and vibration
   B. Siltation and clogging
   C. Sliding, overturning, uplift and piping
   D. Evaporation and seepage only
   Answer: C. Structural safety includes these modes, with cut-offs and scour protection. (Key point: Stability)

## Related in Hydropower Engineering

- [RoR headworks arrangement and functional requirements](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-headworks-arrangement-requirements) — Hydropower Engineering, chapter 5, asked 3×
- [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

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