Did you know that each body of water on Earth is filled with recycled water? The water cycle, also called the hydrologic cycle, is how the Earth recycles water. The water cycle is how water moves from Earth into the atmosphere and back to Earth.
(If you want to know more about earth science and other cycles, like the rock cycle, check out our post and free printable about the rock cycle.)
How the Water Cycle Works
In the chart below, we can see how the water cycle works.
The Sun warms up the water on the Earth. When the water is warmed up, it becomes a gas called water vapor. The water vapor rises into the atmosphere, and we call this evaporation.
Plants and trees give off water vapor in a process called transpiration.
The moist water vapor collects in the cooler atmosphere and condenses. Have you ever boiled water in a pot covered with a lid? When the lid is lifted on a boiling pot of water, there are water droplets on the bottom side. These droplets form when the boiling water steam cools and condenses onto the lid. This condensation process in our atmosphere creates clouds.
The clouds become heavy with water droplets, and soon the clouds cannot hold all the water. The water falls from the sky in the form of snow, rain, sleet, or hail. This is called precipitation.
The precipitation falls into the ocean, lakes, rivers, streams, ponds, and other bodies of water. The precipitation also falls onto the ground. Once it reaches the ground, the precipitation will either run off into bodies of water, soak into the ground where it might seep back into a body of water, or evaporate into the atmosphere and condense into a cloud.
Deposition is a process in which water vapor (gas) changes directly into ice (solid) without going through the liquid phase. In the water cycle, deposition occurs when water vapor in the atmosphere is cooled below its dew point, causing it to change from a gas directly into ice crystals, without first forming liquid droplets.
Deposition usually happens in the upper atmosphere at high altitudes where temperatures are extremely low, and water vapor can freeze directly onto surfaces like tree branches, rooftops, and even the ground. This process is an important part of the water cycle, as it helps with the formation of snow and ice, which later melts to form rivers, lakes, and groundwater.
Deposition is an important process in the water cycle where water vapor changes directly into ice without going through the liquid phase.
Infiltration is the process by which water on the ground surface enters into the soil. It is an important part of the water cycle because it allows water to be stored underground and recharges groundwater reserves. In the early mid-2000’s our area of the country (North Carolina) experienced a severe drought for several years. Many of the groundwater reserves were at dangerous levels. We were on well water at that time and our local municipality had to implement fines for non-essential water use (water grass, washing cars, etc.)
When precipitation falls onto the ground, it can either run off the surface (called surface runoff) or infiltrate into the soil. The amount of water that infiltrates depends on several factors, such as the soil type, vegetation cover, and slope of the land.
Surface flow is the movement of water across the surface of the earth. The surface flow transports water from one location to another. It happens when precipitation falls onto the land and moves downhill, either as runoff or as flow in rivers, lakes, and other bodies of water.
The amount of rain, the slope of the land, and the type of soil all affect surface flow. When there is heavy rain or a large amount of flowing water from melting snows, then floods, landslides, and erosion can happen.
Percolation is the process by which water moves through the spaces in soil or rock layers and enters into underground aquifers. It is an important part of the water cycle, as it allows water to be stored and replenished in underground reserves. (An aquifer is a layer of permeable rock, soil, or sediment that can store and transmit water underground. It provides a storage and distribution system for groundwater.)
Below are the instructions for making a simple model of the water cycle. Years ago, as part of a science co-op our robotics team did year-round, the kids created a more involved model using an empty aquarium. We put rock, soil, and clumps of grass in it, jar lids (for lakes), and built up “mountains” with lots of dirt. So, you can take this further and do a more elaborate model.
Make a Model of the Water Cycle
Learn How the Water Cycle Works
- 2 large bowls a coffee cup will need to sit on the inside of one of the bowls.
- 1 coffee mug or small glass
- 2 rubber bands The rubber bands need to be large enough to go over the bowls, or you can tape the plastic wrap to the bowls to make a secure seal.
- 1 pitcher of water at room temperature
- Place the coffee mugs upright on the bottom of the bowls. Place one mug per bowl.
- Fill each bowl 1/4 full of room temperature water. Be careful not to pour any water into the coffee mugs.
- Cover the bowls tightly with plastic wrap and secure them with a rubber band or tape. Cover the mug and all with plastic wrap.
- Place one bowl in a shady location and the other bowl in a sunny location.
- Record the “start” time on the datasheet in the printable listed on this post. The start time is the time when you place the mini-water cycle in its location. Then, record when you first observed water droplets condense on the plastic wrap. Find the difference between those two times and calculate how long it took for condensation to begin to form.
- Leave these water cycles to sit for several days and observe.
What Is Happening in the Water Cycle Model
Watch as the water evaporates from the bottom of the bowl and rises into the atmosphere, condenses on the plastic wrap, and eventually falls back to the ground as precipitation. Let sit for several days. Keep checking the water in the coffee mug/small glass.
Can you explain what is happening in the model using the words evaporation, condensation, collection, and precipitation?.
Try other test conditions: use hot and cold water to see if the starting water temperature affects the evaporation rate. Another test would involve placing ice cubes in one bowl only. Then, place the bowls side by side, so the only variable that is different between the two is whether there is ice in the bowl or not. How does this affect the time it takes for water droplets to condense onto the plastic wrap?
How can you make a larger model using an old fish tank? How could you model transpiration and surface runoff?
Download the Free Water Cycle Lesson and Printable
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Additional Resources About the Water Cycle
- An interactive water cycle from the USGS. There are three levels; this link is to the itermediate link, but the other links are in the top right corner of the page.
- Water Cycle diagram in MANY languages from the US Geological Survey
- More about infiltration and the water cycle
- More about groundwater storage and the water cycle