Full Text
Th e W at er C yc le Definitions: Condensation – The process by which a vapor becomes a liquid; the opposite of evaporation Precipitation – Water falling, in a liquid or solid state, from the atmosphere to Earth rain, snow) Evaporation – The conversion of a liquid water) into a vapor (a gaseous state) usually through the application of heat energy Transpiration – Evaporation of water from plants into the atmosphere Evapotranspiration – The loss of water from the soil through both evaporation and transpiration from plants Runoff – Precipitation that flows overland to surface streams, rivers and lakes Ground water – Water found underground in spaces between soil particles Infiltration – The flow of water from the ground surface into the ground Did you know? Pure water is tasteless, odorless, and colorless and exists in only three states. The three states in which water can occur in are: solid (ice), liquid, or gas (vapor). Solid water—Ice is frozen water. When water freezes, its molecules move farther apart, making ice less dense that its liquid form. This means ice is lighter that the same volume of water in its liquid form, and so ice floats. Where is the ice in the image above? What form of water does ice take when it melts? Can you locate and name which part of the water cycle ice becomes when it melts? Liquid water is wet and fluid. This is the form of water with which we are most familiar. We use liquid water in many ways, including washing and drinking. Where do you find the liquid form of water? Where does the liquid form of water that you use come from? Water as a gas—Vapor is always present in the air around us. Water in its liquid form evaporates to become vapor. When the water vapor cools in the atmosphere, it turns into many tiny water droplets. These liquid droplets, in great numbers, form clouds. Project WET – Water Education for Teachers Mission: To reach children, parents, educators, and communities of the world with water education. www.projectwet.org U.S. Agency for International Development www.usaid.gov Things to Think About: Pretend you are a drop of water and trace your path through the water cycle. How many places do you visit? How many different forms of water do you take? What if you remove one of the water cycle processes? What may affect the water cycle? pollution, drought) Precipitation Evapotranspiration Transpiration Evaporation Runoff Ground water Infiltration Evaporation Precipitation Condensation Surface Flow If all the water in the world fit in a one liter container, then the water available for human use would be more than one drop.