Skip Navigation

Water CycleWater Cycle

The Basics

The water we use every day is very old. Just like the Earth itself, it’s been around for billions of years. The Earth has a limited amount of water that always gets recycled. It is in a closed system. Since we do not lose or gain water from other sources, it’s important to protect the water we have.

The water cycle is a natural process that happens when water rotates through different forms (solid, liquid, or vapor). The process improves the quality of water. However, people do things that create water pollution.

Did you know ?

Nearly 97% of the world’s water is salty or otherwise undrinkable. Another 2% is locked in ice caps and glaciers. That leaves just 1% for agricultural, residential, manufacturing, community, and personal needs.

Learn More

Explore the links below to learn about the water cycle, human activities that introduce pollutants into the water cycle, and what we can do to protect our water.

Read About It Read About It

Agricultural Runoff in Tox Town (Tox Town - National Library of Medicine) - Description of what agricultural runoff is and its hazardous effects on the environment.

Effects of Urbanization on Water Quality (U.S. Geological Survey) - Information on the effects of urbanization on water quality, and issues that include population growth, urban runoff, sewage overflow, and pesticides.

Locate Your Watershed (U.S. Environmental Protection Agency) - United States map with links to the location of watersheds in all the states.

Nonpoint Source Pollution - Point Source Pollution (National Ocean and Atmospheric Administration) - Describes what point source pollution is and the effects it has on the environment.

Nonpoint Source Pollution/Pollutants from Nonpoint Sources (National Ocean and Atmospheric Administration) - Describes what nonpoint sources of pollution are and the detrimental effects that occur.

Storm Water and Sewage (Tox Town - National Library of Medicine) - Information on storm water and links to Medline Plus, related topic areas, and specific chemicals found in storms.

Urban and Industrial Runoff (Tox Town - National Library of Medicine) - Information on urban and industrial runoff with links to Medline Plus, related topics, and associated chemicals.

Water (PDF, 216.82 KB)(U.S. Navy and Marine Corp Public Health Center) - PDF with information about the water cycle, drinking water, underground water, and the detrimental impact humans have on water.

Water Science Storytime - Dryville (U.S. Geological Survey) - Online story to teach about water quality.

Watersheds - After the Storm (U.S. Environmental Protection Agency) - Answers to what storm water runoff is, why it is a problem, the effect it has on pollution, and possible solutions.

Games and Activities Games and Activities

Matching Fun Facts Game (U.S. Environmental Protection Agency) - Online matching game to determine how much water humans use during different activities.

The Water Cycle (University of Washington) - Information and several activities to learn about the water cycle.

Water, the Never Ending Story (National Institute of Environmental Health Sciences) - Online storybook about the Earth's water.

Videos Videos

Maya's Documentary (Thinkport) - Short video on where water comes from and the effects water pollution can have.

Water Cycle: Nature's Recycling System (U.S. Department of Agriculture) - Video about the water cycle.

Experiments and Projects Experiments and Projects

Build Your Own Watershed (U.S. Environmental Protection Agency)

Nonpoint Source Pollution (PDF, 17.44 KB)(U.S. Environmental Protection Agency) - PDF of a grade 4-7 activity demonstrating waterfall collection, water quality, and the impact on rivers, streams, and bays.

For Teachers For Teachers

The Watershed Sleuth Challenge (National Environmental Education Foundation) - These lessons provide important information about watersheds, what they are, why they\'re important, and what you can do to protect them.