Activity Overview

Grade: 2nd-5th
Time: 30 minutes to 1 hour
Adult support needed? Generally a self-guided activity, may need some support with set-up.

Ready for some fun? Let’s clean our water the way nature does, using rocks, pebbles and sand. As cities and towns develop, it is very common to replace grass and forest areas with homes, office buildings, streets and sidewalks. Grass and forest areas are permeable surfaces that allow water to move through. Buildings, streets and sidewalks are impermeable surfaces that do not allow water to move through. As cities develop, this change decreases the amount of permeable surface area (grass) and increases the amount of impermeable surface area (cement). Impermeable surfaces prevent water from soaking into the ground, reducing the amount of water stored in underground aquifers. Impermeable surfaces also increase the amount of stormwater runoff, which can cause flooding and increase the amount of pollution flowing into our rivers, streams and Monterey Bay. In this activity, youth will:

  1. Conduct an experiment to discover what happens when it rains on different types of surfaces like grass, rocks and cement.
  2. Learn about how these permeable and impermeable surfaces impact stormwater runoff.
  3. Build a water filter using rocks, pebbles and sand as a model of how permeable materials can help reduce stormwater runoff.

Virtual Activity Guide

It’s as if CWC educators were in the classroom with your students. Join CWC staff as they guide youth through the activity. Youth are taken step by step through the activity. You may choose to use the Virtual Activity Guide instead of the Activity Guide PDF as all the same information is provided in this Virtual Activity Guide.

Supports Next Generation Science Standards:

  • 2-PS1-1. Plan and conduct an investigation to describe and classify different kinds of materials by their observable properties. 
  • 2-PS1-2. Analyze data obtained from testing different materials to determine which materials have the properties that are best suited for an intended purpose. 
  • 5-ESS2-1. Develop a model using an example to describe ways the geosphere, biosphere, hydrosphere, and/or atmosphere interact. 
  • 5-ESS3-1. Obtain and combine information about ways individual communities use science ideas to protect the Earth’s resources and environment. 

Materials Needed:

  • Virtual Activity Guide or Downloadable Activity Guide PDF: Nature’s Water Filter
  • Sponge
  • Pencil
  • Water
  • Plastic bottle
  • Sand (optional)
  • Soil
  • Rocks
  • Cotton balls or pieces of cloth

Downloadable Activity Guide (PDF)

Youth may choose to use the Virtual Activity Guide (see above) or the below downloadable Activity Guide. Both resources will guide the student through the activity.

Click here to download your activity guide (English)

Haga clic aquí para descargar su guía de actividades (Español)


1. View or print the worksheet. No printer? No problem! View the worksheet online and grab blank paper to follow along.

2. Experiment: Follow worksheet instructions to experiment and observe what happens as you “make it rain” on different types of materials.

3. Read the worksheet to learn about the differences between permeable and impermeable materials. Use your knowledge to guess whether each material you tested is permeable or impermeable.

4. Watch these videos by Jasper Fox Sr. and NCTCOG E&D to understand why it matters whether a surface is permeable or impermeable:

5. Read the worksheet to learn how permeable materials help prevent stormwater runoff and keep water clean.

6. Take Action: Follow worksheet instructions and watch the below video by Saint George’s College North to make your own water filter from permeable materials!

Thank you to the City of Santa CruzCity of CapitolaSanta Cruz County and the National Oceanic and Atmospheric Administration for supporting the Coastal Watershed Council’s Watershed Rangers environmental education program.

To all of the Watershed Rangers students, teachers and program partners, although we will not be able to see you in classrooms, field trips and after school programs right now, we hope to provide you and your loved ones with online resources and activities during this time. We know that parents, teacher and lifelong learners are seeking ways to stay engaged and active, and we’re going to be working to bring activities to you through the Coastal Watershed Council blog. Please share these resources and activities with friends, neighbors and parents groups and stay tuned for more.

Additional resources:

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