---
title: "Types of rainwater harvesting"
subject: "Building Technology"
chapter: 12
key: "semester_6/building_technology:rwh-types"
source: https://www.bctengineer.com/q/semester_6/building_technology/rwh-types
site: BCT Engineering
---

# Types of rainwater harvesting

Building Technology · Chapter 12: Other services in building

- Asked in: 2072 Magh, 6 marks
- Video: [Rooftop Rainwater Harvesting (English)](https://www.youtube.com/watch?v=8Ls0rM2j8iQ) — Pranis Creations
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/rwh-types
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-12

## Question

Explain different types of rain water harvesting.

## Short answer

Types include rooftop harvesting (collecting rain from roofs into storage tanks), surface runoff harvesting (collecting from open areas into ponds/reservoirs), and groundwater recharge using recharge pits, trenches, or wells filled with boulders, gravel and sand. Rooftop storage and recharge pits are most common for buildings.

## Answer

#### 1. Rooftop rainwater harvesting (for storage)
Rain from roofs is collected through gutters and pipes and stored in tanks for use (domestic use, gardening). Suited to houses and apartments.

#### 2. Surface runoff harvesting
Rain flowing over the ground (roads, open land, courtyards) is collected in ponds, tanks or reservoirs. Common in rural Nepal and in towns where open areas exist.

#### 3. Groundwater recharge
Rain is led into the ground to raise the water table, by:
- **Recharge pits and trenches** filled with boulders, gravel and sand.
- **Recharge (dug or bore) wells**, through which filtered water goes to the aquifers.
- **Percolation ponds** and gravel-filled recharge shafts.
- Permeable pavements and kerb-side recharge.

#### 4. Direct use vs recharge
Storage tanks give an immediate supply; recharge methods are used where space is limited, or where rainfall is seasonal and storage is uneconomical.

Rooftop storage and recharge pits are the two most common methods for buildings.

## Check yourself

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

1. What is rooftop rainwater harvesting?
   A. Rain falling on the ground is collected in ponds
   B. Rain is pumped into deep bore wells directly
   C. Rain from roofs is collected through gutters and pipes and stored in tanks for use
   D. Rain is spread over the road surface to cool it
   Answer: C. Rooftop RWH collects roof rain through gutters and pipes and stores it in tanks; it suits houses and apartments. (Key point: Rooftop harvesting)

2. How does surface runoff harvesting differ from rooftop harvesting?
   A. It collects rain flowing on ground such as roads and open land into ponds, tanks or reservoirs
   B. It uses only gutters and down pipes
   C. It is used only inside basements
   D. It only recharges groundwater and never stores water
   Answer: A. Surface runoff harvesting collects ground-flowing rain in ponds, tanks or reservoirs, common in rural Nepal and where open areas exist. (Key point: Surface runoff harvesting)

3. Which of the following is a groundwater recharge method?
   A. Overhead plastic tank
   B. Recharge pits, trenches, recharge wells and percolation ponds
   C. First-flush diverter
   D. Wet riser
   Answer: B. Groundwater recharge uses recharge pits and trenches, dug or bore wells, percolation ponds and permeable pavements to raise the water table. (Key point: Recharge methods)

4. When are recharge methods preferred over storage tanks?
   A. When immediate supply is needed
   B. When space is limited or rainfall is seasonal and storage is uneconomical
   C. When rainfall is spread evenly all year and space is plentiful
   D. When the roof is made of GI sheet
   Answer: B. Storage gives immediate supply, but recharge suits limited space or seasonal rainfall where large storage is uneconomical. (Key point: Storage vs recharge)

## Related in Building Technology

- [Rainwater harvesting and its treatment](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Arwh-treatment) — Building Technology, chapter 12, asked 3×
- [Components of rainwater harvesting](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Arwh-components) — Building Technology, chapter 12, asked 2×
- [Short note: Rainwater harvesting](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Arainwater-harvesting-note) — Building Technology, chapter 12, asked 5×
- [Benefits of rainwater harvesting](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Arwh-benefits) — Building Technology, chapter 12