How Much Rain Can You Catch?
Designing Rainwater Harvesting Systems
Grade Levels: 4–8 (Adaptable for Grades 3–10)
Time Required:
2–3 class periods (45–60 minutes each)
2–3 class periods (45–60 minutes each)
Subject Areas
- Science
- Engineering
- Mathematics
- STEM
- Social Studies
- Environmental Science
Essential Question: How can engineers design systems that help communities collect clean water?
Driving Question: How can we design a rainwater harvesting system that collects the greatest amount of water while using limited materials?
Learning Objectives
Students will:
- Explain how rainwater harvesting works.
- Describe why rainwater harvesting is important around the world.
- Calculate how much rainwater can be collected from a roof.
- Apply the Engineering Design Process.
- Build, test, and improve a rainwater harvesting model.
- Analyze data to improve their designs.
Real-World Connection
Over 2 billion people lack access to safely managed drinking water.
Many communities rely on rainwater harvesting to provide water for:
Over 2 billion people lack access to safely managed drinking water.
Many communities rely on rainwater harvesting to provide water for:
- Drinking (after treatment)
- Cooking
- Washing
- Irrigation
- Livestock
Engineers help design systems that collect as much water as possible while keeping it clean.
H2O for Life Connection
H2O for Life Connection
H2O for Life partners with schools around the world to improve access to clean water. Many schools use rainwater harvesting systems to collect water during rainy seasons so students have water throughout the year.
Vocabulary
- Rainwater Harvesting
- Catchment Area
- Roof Runoff
- Surface Area
- Gallons
- Runoff
- Collection Tank
- Engineering Design Process
- Prototype
- Iteration
- Constraint
- Optimization
Materials
Per Group
- Cardboard
- Cardstock
- Popsicle sticks
- Clay
- Tape
- Plastic cup
- Plastic container
- Ruler
- Calculator
- Watering can or spray bottle
- Measuring cup
- Stopwatch
Teacher
- Funnel
- Bucket
- Water
Engage (10 min)
Show students photos of homes with rainwater collection systems.
Ask:
"If your house lost running water tomorrow, how would you collect enough water for your family?"
"If your house lost running water tomorrow, how would you collect enough water for your family?"
Students complete a Think-Pair-Share.
Explore Part 1
How Much Rain Can You Catch?
Students first calculate how much water a roof can collect using measurements, roof area, rainfall amounts, and the conversion factor from rainfall to gallons.
Students learn:
- Roof surface area
- Rainfall measurements
- Gallons collected
- Mathematical modeling
Explore Part 2
Students investigate:
Which roof shapes collect the most water?
Which roof materials might lose water?
Why do gutters matter?
Explain
Mini Lesson
Introduce:
How rainwater systems work
Roof
↓
Gutters
↓
Downspout
Downspout
↓
First Flush Diverter
First Flush Diverter
↓
Storage Tank
↓
↓
Filter
↓
Community Use
Discuss why some countries depend on rainwater more than groundwater.
This lesson was designed by Alison Barrett, University of Arizona Cooperative Extension