---
title: "Pre-feasibility versus feasibility studies"
subject: "Hydro Power"
chapter: 3
key: "semester_6/hydro_power:prefeasibility-vs-feasibility"
source: https://www.bctengineer.com/q/semester_6/hydro_power/prefeasibility-vs-feasibility
site: BCT Engineering
---

# Pre-feasibility versus feasibility studies

Hydro Power · Chapter 3: Planning of Hydropower Projects

- Asked in: 2075 Bhadra, 4 marks
- Video: [Micro Hydro Pre-feasibility Study: A Technical Guideline](https://www.youtube.com/watch?v=KoWNXssTyCg) — Practical Action
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/hydro_power/prefeasibility-vs-feasibility
- Whole chapter: https://www.bctengineer.com/md/semester_6/hydro_power/chapter-3

## Question

Explain the differences between Pre-feasibility and Feasibility studies in hydropower projects.

## Short answer

Pre-feasibility screening alternatives to select the best layout with approximate costs (±25–30%). Feasibility study detailly confirms the chosenscheme 's technical, economic, and environmental viability with refined costs (±10–15%) to secure financing.

## Answer

**Pre-feasibility study** is a preliminary study that compares alternative layouts of a hydropower site and selects the most promising one. **Feasibility study** is a detailed study of the selected scheme to prove that it is technically, economically, financially and environmentally viable and ready for financing.

| Point | Pre-feasibility study | Feasibility study |
|---|---|---|
| Purpose | Screen alternatives and choose the best | Confirm viability of the chosen scheme |
| Stage | After reconnaissance/desk study | After pre-feasibility, before detailed design |
| Data | Existing maps (1:50,000), short or regional hydrology | Detailed survey (1:1000–1:5000), site flow measurement |
| Investigations | Surface geological mapping, few tests | Drilling, test pits, seismic survey, material tests |
| Design | Conceptual layouts, rough sizes | Optimised layout, preliminary design of all structures |
| Cost estimate accuracy | About ±25–30% | About ±10–15% |
| Environment | Initial screening of impacts | Full IEE/EIA |
| Output | Recommended alternative, go/no-go | Bankable report: B/C, IRR, financing plan |
| Cost and time | Low, a few months | High, one to two years |

In short, the pre-feasibility study answers "which option is best?", and the feasibility study answers "is this option worth building, and how?".

## Check yourself

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

1. What is the main purpose of a pre-feasibility study?
   A. Screen alternative layouts and choose the most promising
   B. Produce the bankable report
   C. Do final drawings
   D. Construct the plant
   Answer: A. Pre-feasibility compares alternatives; feasibility confirms the chosen scheme. (Key point: Purpose)

2. Which pair of cost estimate accuracies is correct?
   A. Pre-feasibility +-10-15%, feasibility +-25-30%
   B. Both +-5%
   C. Pre-feasibility +-25-30%, feasibility +-10-15%
   D. Both +-50%
   Answer: C. The estimate gets more accurate with detailed investigation. (Key point: Cost accuracy)

3. Which belongs to a feasibility study?
   A. Only existing 1:50,000 maps
   B. Drilling, seismic survey and site flow measurement
   C. No geological work
   D. Only desk study
   Answer: B. Feasibility uses detailed surveys and drilling; pre-feasibility uses existing maps and surface mapping. (Key point: Data and investigations)

## Related in Hydro Power

- [Power sources and hydro versus thermal](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Apower-sources-hydro-vs-thermal) — Hydro Power, chapter 3
- [Types of intakes and their suitability](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aintake-types) — Hydro Power, chapter 5, asked 2×
- [Flow duration curve and planning parameters](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Afdc-planning-parameters) — Hydro Power, chapter 3
- [Spillway types suitable for Nepalese rivers](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aspillway-types-nepal) — Hydro Power, chapter 6
- [Spillways, gates and types of spillways](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aspillways-and-gates) — Hydro Power, chapter 6

## Related in other subjects

- [Studies in reconnaissance, pre-feasibility, feasibility](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Arecon-prefeas-feas-studies) — Hydropower Engineering, chapter 2, asked 3×
- [Pre-feasibility vs feasibility; site investigations](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aprefeasibility-vs-feasibility-investigations) — Hydropower Engineering, chapter 2
- [Development phases; pre-feasibility factors](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Adev-phases-prefeasibility-factors) — Hydropower Engineering, chapter 2
- [Pre-feasibility site-specific investigations](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aprefeasibility-site-investigations) — Hydropower Engineering, chapter 2