THE WATER CYCLE The Water Cycle

Nature is always moving water through the air, land, and plants… What is the Water Cycle? The water cycle Nature is always moving water through the air, land, and plants… so that the water we use is constantly recycled

Evaporation: The process of turning from a liquid to a gas or vapor. The Water cycle Evaporation: The process of turning from a liquid to a gas or vapor. With the energy from the sun, water rises with the air high up into the troposphere During this process impurities and salts in the water are left behind

transpiration The water cycle During the process of photosynthesis, plant lose water vapor to the atmosphere This process of evaporation through plant leaves is called transpiration In large forests, an enormous amount of water will transpire through leaves

Humidity and Relative humidity The amount of water vapor in the air is called the humidity. When the air has the maximum amount of water vapor it can hold it is said to be saturated. The amount of water it takes to reach saturation is dependent on temperature therefore it is more productive to talk about Relative humidity. Relative Humidity: The amount of water in the air compared to the maximum it can hold. (expressed as a percentage)

condensation The water cycle The air temperatures decrease as the water vapor rises into the troposphere Water droplets form to create clouds when the air reaches a specific temperature called the Dew Point This process of going from a vapor to a liquid is called condensation

Water falls from the clouds as rain, snow, sleet, or hail Precipitation The water cycle Water falls from the clouds as rain, snow, sleet, or hail

Runoff The water cycle Some water stays on the earth’s surface and flows into rivers, lakes, reservoirs, etc. Then the cycle begins again, as water from the earth’s surface evaporates into the atmosphere

Infiltration Some water on the surface will enter the soil through infiltration and eventually reach groundwater. Different surfaces have different infiltration rates

About 75 percent of the earth’s surface is covered by water Why is it important to preserve water? The water cycle About 75 percent of the earth’s surface is covered by water But only 0.01 percent of this is available for living organisms to use The rest is “locked up” as salt water or is frozen in polar ice caps and glaciers