---
title: "Site investigation for micro hydro plant"
subject: "Energy Resources"
chapter: 5
key: "semester_6/energy_resources:micro-hydro-site-investigation-head-measurement"
source: https://www.bctengineer.com/q/semester_6/energy_resources/micro-hydro-site-investigation-head-measurement
site: BCT Engineering
---

# Site investigation for micro hydro plant

Energy Resources · Chapter 5: Micro and small hydro power systems

- Asked in: year not given, 5 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/energy_resources/micro-hydro-site-investigation-head-measurement
- Whole chapter: https://www.bctengineer.com/md/semester_6/energy_resources/chapter-5

## Question

Describe the investigations required to select a site for a micro hydropower plant. Explain any three methods of measuring the head of a site.

## Short answer

Site investigation assesses flow, head, geology, access, environment and load. Head measurement methods: water-filled tube with pressure gauge (head from pressure reading), spirit level and measuring stick (step-wise vertical drop), Abney level (height = L sinθ). Dumpy level gives highest accuracy.

## Answer

Site investigation decides whether the available flow and head can be developed safely and cheaply.

#### Investigations
1. **Reconnaissance:** study of maps and a field walk to find possible intake, canal, forebay and powerhouse positions, and the demand (load) of the nearby village.
2. **Head measurement:** the gross head between the intake water level and the tailrace level.
3. **Flow measurement:** dry-season (minimum) and mean flow, from direct measurement or hydrological estimates.
4. **Geology and soil:** stable slopes, with no landslides or leaking ground along the canal and penstock; foundations for the powerhouse and anchor blocks.
5. **Layout and cost:** length of canal and penstock, access, flood level at the powerhouse, distance to the load.
6. **Environment and water rights:** impact on downstream users and fish, and on irrigation and drinking water needs.

#### Head measurement methods
- **Water-filled tube (pipe) and pressure gauge:** a long flexible tube filled with water is laid down the slope; the gauge reading at the lower end gives the head, $H = p/(\rho g)$. For long drops, readings are taken in steps and added.
- **Spirit level and measuring stick:** a level is used to measure the height difference in successive steps along the slope, and the steps are added. It is cheap and quite accurate for short drops.
- **Abney level (clinometer):** the slope angle $\theta$ is measured along a measured length $L$, and the height of each step is $L\sin\theta$. It is quick and suits long, steep slopes.
- **Altimeter or GPS:** readings at the top and bottom give an approximate height difference, with an error of a few metres, so it is used only in the first survey.
- **Dumpy level / theodolite:** gives the most accurate result in the detailed survey.

The net head is the gross head minus friction and bend losses in the penstock (typically 5–10 % of the gross head).

## Check yourself

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

1. Which flow is investigated for dependable power?
   A. Flood flow
   B. Dry-season (minimum) flow
   C. Monsoon peak
   D. Annual maximum
   Answer: B. Plant must supply power in dry season. (Key point: Flow for design)

2. In the water-filled tube method, head is found from...
   A. H = p/(ρg) from the gauge at the lower end
   B. H = ρg/p
   C. H = Q/A
   D. H = v²
   Answer: A. Readings are taken in steps for long drops. (Key point: Water-filled tube)

3. How is net head obtained?
   A. Gross head plus losses
   B. Gross head times flow
   C. Head at the intake only
   D. Gross head minus friction and bend losses in the penstock (about 5-10%)
   Answer: D. Losses reduce the head available. (Key point: Net head)

## Related in Energy Resources

- [Micro hydro net head, power and energy](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Amicro-hydro-power-output-numerical) — Energy Resources, chapter 5
- [Micro hydro scheme components and classification](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Amicro-hydro-scheme-components-classification) — Energy Resources, chapter 5

## Related in other subjects

- [Purposes of site investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asite-investigation-purposes) — Engineering Geology II, chapter 4, asked 7×
- [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
- [Pre-feasibility site-specific investigations](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aprefeasibility-site-investigations) — Hydropower Engineering, chapter 2
- [Methods of surface and subsurface site investigation](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Amethods-of-surface-and-subsurface) — Engineering Geology I, chapter 1, asked 4×