Water moves from place to place in a process known as the water cycle. Water flows freely in streams, is pooled in oceans and lakes, trickles through underground springs, percolates through the soil and is stored as a solid in glaciers and snow.  Water is also present in the atmosphere as droplets or ice crystals in clouds and vapor.

When the sun heats up rivers, lakes or oceans, some of the water turns to steam and is released into the atmosphere.   This process is called evaporation.  Plants also release small amounts of water as a gas through their leaves in a process called transpiration.

Water in the atmosphere condenses and forms clouds.  Water falls back to  earth as precipitation such as rain, snow, sleet or hail.

Water that falls in places that are very cold may freeze, storing the water in a solid form.  If the temperature warms, snow or ice may melt, releasing the water in liquid form. 

When water falls as a liquid or is released from melting ice or snow, it may flow into the small spaces between rocks and soil.  Through this process, called infiltration, water may remain in place as groundwater or slowly travel through the earth to meet up with a surface body of water.

When water does not seep into the soil, but flows over the surface of the ground it is called runoff.  Water that travels over the surface often ends up in a river or lake.

Click the water droplet for an animation of the water cycle. You will be directed to the EPA Water Cycle page.  To return, close the EPA window on your browser.