The Water cycle
Earth's water is always in movement, and the natural water cycle, also known as the hydro cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years. By now, you know that the water cycle describes the movement of Earth's water. If you check back in a thousand or million years, no doubt these numbers will be different! Notice how of the world's total water supply of about 332.5 million square miles of water, over 96 percent is saline. And, of the total freshwater, over 68 percent is locked up in ice and glaciers. Another 30 percent of freshwater is in the ground. Fresh surface-water sources, such as rivers and lakes, only constitute about 22,300 square miles, which is about 1/150th of one percent of total water. Yet, rivers and lakes are the sources of most of the water people use everyday. This is the water cycle please enjoy this presentation
The Start of the Water Cycle is Evaporation
Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gas that is not saturated with the evaporating substance. The other type of vaporization is boiling, which is characterized by bubbles of saturated vapor forming in the liquid phase.A very small amount of water vapor enters the atmosphere through heat vaporizing, the process by which water changes from a solid (ice or snow) to a gas, bypassing the liquid phase. This often happens in the Rocky Mountains as dry and warm winds blow in from the Pacific in late winter and early spring. When a Chinook takes effect local temperatures rise dramatically in a matter of hours. When the dry air hits the snow, it changes the snow directly into water vapor, bypassing the liquid phase. Heat vaporizing is a common way for snow to disappear quickly in arid climates.
Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. Transpiration is essentially evaporation of water from plant leaves.Plants put down roots into the soil to draw water and nutrients up into the stems and leaves. Some of this water is returned to the air by transpiration (when combined with evapration, is the total process is known as evopartion. Transpiration rates vary widely depending on weather conditions, such as temperature, humidity, sunlight availability and intensity, precipitation, soil type and saturation, wind, land slope, and water use and diversion by people. During dry periods, transpiration can contribute to the loss of moisture in the upper soil zone, which can have an effect on vegetation and food-crop fields.
Condensation is the change of water from its gaseous form (water vapor) into liquid water.Condensation generally occurs in the atmosphere when warm air rises, cools and looses its capacity to hold water vapor. As a result, excess water vapor condenses to form cloud droplets.You don't have to look at something as far away as a cloud to notice condensation, though. Condensation is responsible for ground-level fog, for your glasses fogging up when you go from a cold room to the outdoors on a hot, humid day, for the water that drips off the outside of your glass of iced tea, and for the water on the inside of the windows in your home on a cold day is all condensation.
The clouds floating overhead contain water vapor and cloud droplets, which are small drops of condensed water. These droplets are way too small to fall as precipitation, but they are large enough to form visible clouds. Water is continually and condensing in the sky. If you look closely at a cloud you can see some parts disappearing (evaporating) while other parts are growing (condensation). Most of the condensed water in clouds does not fall as precipitation because their fall speed is not large enough to overcome updrafts which support the clouds. For precipitation to happen, first tiny water droplets must be compact on even tinier dust, salt, or smoke particles, which act as a nucleus. Water droplets may grow as a result of additional condensation of water vapor when the particles collide. If enough collisions occur to produce a droplet with a fall speed which slows the cloud updraft speed, then it will fall out of the cloud as precipitation. This is not a trivial task since millions of cloud droplets are required to produce a single raindrop. A more efficient mechanism for producing a precipitation-sized drop is through a process which leads to the rapid growth of ice crystals at the expense of the water vapor present in a cloud. These crystals may fall as snow, or melt and fall as rain.
A runoff is when the water from precipitation goes to the water storage.Surface (also known as overland flow) runoff is the flow of water that occurs when excess storm water, melt water, or other sources flows over the earth's surface.When rain or snow falls onto the earth, it just doesn't sit there, it starts moving according to the laws of gravity. A portion of the precipitation seeps into the ground to replenish Earth's ground water. Most of it flows downhill as runoff. Runoff is extremely important in that not only does it keep rivers and lakes full of water, but it also changes the landscape by the action of erosion. Flowing water has tremendous power—it can move boulders and carve out canyons; check out the Grand Canyon!
The water cycle sounds like it is describing how water moves above, on, and through the Earth ... and it does. But, in fact, much more water is "in storage" for long periods of time than is actually moving through the cycle. The storehouses for the vast majority of all water on Earth are the oceans.Of course, nothing involving the water cycle is really permanent, even the amount of water in the oceans. Over the "short term" of hundreds of years the oceans' volumes don't change much. But the amount of water in the oceans does change over the long term. During the last Ice Age, sea levels were lower, which allowed humans to cross over to North America from Asia at the (now underwater) Bering Strait.