Earth Systems (B): REVIEW: Follow a Water Molecule Through the Hydrologic Cycle

REVIEW: Follow a Water Molecule Through the Hydrologic Cycle

Follow a Water Molecule Through the Hydrologic Cycle

The following steps illustrate the path that water follows as it circulates from one reservoir to another on earth through the hydrologic cycle.

1. In the atmosphere, water vapor is cooled and condenses to form clouds.

2. Water returns to earth's surface as precipitation - rain, snow, sleet, hail, etc.

3. Once on the ground, the water cycle continues through infiltration, where some of the water can percolate through the soil and become stored as groundwater. There are several factors that influence the movement and infiltration of water: rock & soil type, man-made surfaces, vegetation, and topography. Man-made surfaces do not absorb water as readily as natural surfaces, which leads to an increase in runoff. Steeper slopes cause water to run off more quickly, which prevents much water from infiltrating the ground.

4. Water that does not infiltrate the ground is called surface runoff. Water flows over the land and into creeks, streams, rivers, lakes, and eventually to the ocean. Heavy precipitation and snowmelt can move too quickly to infiltrate the ground and also become runoff. Runoff is important because it replenishes Earth's surface water.

5. Water from Earth's surface can be returned to the atmosphere via evaporation & transpiration (together, they are know as evapotranspiration). Evapotranspiration is caused by the Sun's energy, which converts liquid water into water vapor.

6. When there is too much water vapor in the atmosphere, condensation occurs and clouds form. We are now back to step 1 and the cycle repeats!

Source: Teachers' Domain, The Hydrologic Cycle, published December 17, 2005, retrieved on June 7, 2010,
http://www.teachersdomain.org/resource/ess05.sci.ess.watcyc.hydrocycle/

Last modified: Thursday, 15 July 2010, 2:53 PM

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