Understanding the Water Cycle
(For middle school & up)
1. What Is the Water Cycle?
The water cycle (also called the hydrologic cycle) is the continuous movement of water on,
above, and below Earth’s surface. Water changes its state—liquid, vapor, ice—as it
circulates, keeping life on Earth possible.
2. Main Stages
1. Evaporation
○ Heat from the sun turns liquid water from oceans, lakes, and rivers into water
vapor.
2. Condensation
○ Water vapor rises, cools, and changes back into tiny liquid droplets, forming
clouds.
3. Precipitation
○ Clouds release water as rain, snow, sleet, or hail, depending on temperature.
4. Collection (Runoff & Groundwater)
○ Water collects in oceans, rivers, lakes, or seeps into the ground, replenishing
aquifers.
3. Why It Matters
● Climate regulation: Distributes heat and moisture globally.
● Freshwater supply: Keeps rivers and reservoirs filled.
● Ecosystem support: Plants, animals, and humans all depend on it.
4. Quick Facts
● About 97% of Earth’s water is in the oceans (saltwater).
● The average water molecule can spend thousands of years in the ocean before
cycling again.
● Human activities (deforestation, urbanization) can disrupt natural water flow.
5. Check Your Understanding
● What drives the energy for the water cycle?
● Which stage turns vapor into liquid?
● How do humans impact the cycle?
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