The Water Cycle The stages of the water cycle are storage (water being stored in Earth in lakes, streams, and the water table below ground); Evaporation (liquid turning into gas); Condensation (gas turning into liquid); and precipitation (water in liquid form Ð rain Ð or solid form Ð snow- falling from sky to earth). We will talk about each of these stages. Storage Liquid water is stored in the ocean. It then evaporates, turning into water vapor gas. Water is also stored in planets. When water is given off by plants through photosynthesis it goes into the atmosphere as water vapor. This process is called transpiration. Different parts of the earth store different amounts of water. The oceans, seas and bays store the most, at 96.5 percent. This storage is all salt water (also called saline). Ice caps at the north and south pole, glaciers and permanent snow is next at 1.74 percent. This is 68.7 percent of all fresh water (no salt in it). Ground water stores the next most amount at 1.7 percent. 30.1 percent of freshwater is stored in ground water and .94 percent of salt water is stored as groundwater. Soil holds 0.001 or one thousandths percent of water (fresh water ). Ground ice and permafrost holds 0.022 percent water. Lakes only hold 0.013 or 13 thousandths percent. The atmosphere only holds 0.001 or one thousandths of a percent of the water in the world. Then we have swamps, rivers and water in living things, all hold in the ten thousandths of a percent. So to sum it up, most water is in the oceans and it is saline or salt water. Most fresh water is locked up in the polar ice and glaciers. Of all the water in the world, most (97 percent) is saline water in the ocean. Only 3 percent is fresh water. Of the 3 percent fresh water, 68.7 percent is in ice caps and glaciers. 30.1 percent is is ground water and only 0.9 or 9 tenths of a percent is on the surface. Most of that surface water is in lakes (87 percent) and swamps have 11 percent. Evaporation Evaporation is the process by which liquid water changes to water vapor and enters the atmosphere as a gas. Every day about 1,200 cubic kilometers (which is about 290 cubic miles) of water evaporates from the ocean, land, plants, and ice caps. Evaporation takes energy from the environment to change the liquid molecules into gas. Condensation Small particles in the air become surfaces on which water vapor can condense and form cloud droplets. These particles are called condensation nuclei. Sources of cloud condensation nuclei can be both natural and human-caused. Natural sources of cloud condensation nuclei include volcanic dust, sea spray salt, and bacteria. Humans also release unnatural chemicals into the air from the burning of fossil fuels and from industrial sources. One example is photochemical smog. (chemicals that interact with sunlight to make pollution). The size of the average raindrop is gigantic compared to the average size of a condensation nuclei. An average size rain drop is about 2 millimeters where an average condensation nuclei size is 2 ten-thousandths of a millimeter. Clouds are made up of water droplets. Think about walking through fog. You feel wet. Fog is just a cloud at ground level. Condensation is the process where water vapor in the atmosphere is returned to its original liquid state. Condensation may appear as clouds, fog, mist, dew or frost. Condensation of water vapor occurs when the temperature of the air is lowered to its dew point. The dew point is the temperature where the air is holding all the water vapor it can hold. When air is cooled, relative humidity increases, until at a particular temperature, called the dew point, the air becomes saturated. Further cooling below the dew point will induce condensation of the excess water vapor. Relative Humidity (RH) is a percent. It is the amount of actual water vapor in the air (actual vapor density) divided by the amount of water vapor the can hold at its temperature (saturation vapor density) then multiply by 100. So temperature determines condensation. The land can also help condesation occur. Orographic Lifting is when air is raised into the atmosphere because it has come to a mountain and it has to rise. The air rises along the mountain and cools causing condensation. Frontal wedging is when air gets pushed up from behind by other air that is colder. The air in front rises and condenses. Imagine water vapor with 50 percent saturation (so it is already holding 50 percent of the water vapor it can hold). In case one it is rising away from the earth and in case two it is falling towards earth. In which case will it reach the dew point? Where the air is falling there will be high pressure at the earthÕs surface. Where the air is rising there will be low pressure at the surface. Precipitation Condensed water droplets combine to form large drops. This process is called coalescence. These drops then fall to earth. They can fall as rain, snow, sleet or hail. Runoff Surface runoff is when water flows down the surface of the earth into streams and rivers. Groundwater is water that flows though rocks and soil and goes underground. Some of this underground water can flow into streams and the ocean. This is called surface runoff or subsurface runoff. Latent Heat Latent heat is the energy given out or absorbed by a substance when it changes state like going from a solid to a gas. Latent heat is the heat energy involved in the phase change of water. Latent heat is gained by water molecules when water evaporates. The heat added during evaporation is used to break hydrogen bonds between water molecules and does not raise the temperature of the water body. The heat then is "hidden" or stored in the water molecule until it is released during condensation. At that point, the heat is converted into sensible heat or heat you can sense through temperature. Latent heat released during condensation is an important source of energy to drive atmospheric systems like hurricanes and cumulus clouds. Heat is given out to the environment in the following three changes. 1. When gas like water vapor changes into liquid like rain (condensation). 2. When liquid like rain changes into a solid like ice (freezing). 3. When a gas like water vapor changes into a solid like ice (sublimation). Heat is taken in from the environment in the following thee changes. 1. When a solid like ice changes into a liquid like rain (melting). 2. When a liquid like rain changes into a gas like water vapor (evaporation). 3. When a sold like ice changes into a gas like water vapor (sublimation). This heat energy released into the environment becomes important when talking about storms like hurricanes.