The water cycle includes several processes, all of which keep it continually flowing. These processes are known as evaporation, transpiration, condensation, and precipitation. Also included are Infiltration, surface runoff, groundwater, and absorption.
Most everyone has learned about the tradition water cycle. There’s evaporation, which is simply the process by which a liquid becomes a gas, (1 and 9) transpiration, which is the same thing as evaporation except that the water vapor is being released from pores in the leaves of plants, (2 and 9) condensation, the cooling of water in the air so it reverts to its liquid state, (3 and 9) and, finally, there is precipitation, where the water falls back to earth in the familiar forms of rain, snow, sleet, and hail. (4 and 9)
What most people miss is that there’s more to it than that. For instance, once the water falls as rain, where does it go? Sure, it eventually gets back into the oceans, but not all water falls over streams and rivers, so where does the water that falls over land go? Most of it flows over the land as surface runoff which eventually flows into the streams and rivers. Surface runoff is water that just flows overtop of the soil, like the little rivulets of water you see going down the sides of your road when it rains. (6 and 9) It just keeps flowing until it either is absorbed into the ground (5 and 8) or makes its way into a stream or river. But that begs the question, what happens to the water that is absorbed into the ground? Most of it stays in the upper layers of soil (5) and will eventually be picked up by plant roots, make its way horizontally into a streambed, or evaporate as the ground dries. Some however will penetrate further into the ground and reach aquifers, becoming part of the ground water that we drink and use every day. (7)
Everyone is aware of the fact that rivers and streams swell when it rains. Just as most people know that creeks flow into streams, which flow into rivers, which flow into still larger rivers, which eventually empty into lakes or oceans. Some rivers, such as the Nile River in Egypt, flood annually due to heavy precipitation. While the Nile no longer does, courtesy of a dam built to control such things, the fact remains that without it, the heavy summer rains further upstream would cause the river to burst its banks. (10) Rivers are affected by the surface runoff. This runoff is heated by roads and parking lots, and it picks up a lot of sediments from the land it flows over. When it is deposited into the river it can have serious effects on the water quality of the river. (6) Land use decisions can reduced the amount of surface runoff and keep unnecessary sediments from the rivers.


1. http://ga.water.usgs.gov/edu/watercycleevaporation.html; Last modified February 08, 2011; USGS; Page Contact Information: Howard Perlman
2. http://ga.water.usgs.gov/edu/watercycletranspiration.html; Last modified July 1, 2011; USGS; Page Contact Information: Howard Perlman
3. http://ga.water.usgs.gov/edu/watercyclecondensation.html; Last modified November 18, 2011; USGS; Page Contact Information: Howard Perlman
4. http://ga.water.usgs.gov/edu/watercycleprecipitation.html; Last modified February 08, 2011; USGS; Page Contact Information: Howard Perlman
5. http://ga.water.usgs.gov/edu/watercycleinfiltration.html; Last modified February 08, 2011; USGS; Page Contact Information: Howard Perlman
6. http://ga.water.usgs.gov/edu/watercyclerunoff.html; Last modified February 08, 2011; USGS; Page Contact Information: Howard Perlman
7. http://ga.water.usgs.gov/edu/earthgw.html; Last modified February 08, 2011; USGS; Page Contact Information: Howard Perlman
8. http://water.usgs.gov/wsc/glossary.html; Last modified February 10, 211; USGS; U.S. Department of the Interior and U.S. Geological Survey
9. http://www.nwrfc.noaa.gov/info/water_cycle/hydrology.cgi; Northwest River Forecast Center; NOAA; National Oceanic and Atmospheric Administration
10. http://www.touregypt.net/featurestories/nile.htm; ©1996-2011 Tour Egypt. All Rights Reserved; Web development: AKNsolutions.com


