The Water Cycle What is it? The earth has a limited amount of water. That water keeps going around and around and around and around and (well, you get the idea) in what we call the "Water Cycle". Water moves through the Earths ecosystem. This cycle is made up of a few main parts: evaporation (and transpiration) condensation precipitation collection (groundwater) Evaporation It is the process of liquid water changing into water vapor. This vapor joins the other gases in the atmosphere. As it rises high into the air, the water vapor cools. If the water cools enough, it will condense. Condensation: This is the process in which water vapor changes into liquid water. When water condenses, clouds form. Drops of condensed water in the clouds collide, and the drops grow larger. When drops are too heavy to remain suspended in the clouds by air currents, they fall as precipitation. Precipitation: This is solid or liquid water that falls from the air and returns to Earth. Rain, snow, sleet, and hail are forms of precipitation. Most precipitation falls back into the oceans. It can also land on the ground and run off the surface into rivers/lakes, or it can soak into the ground. Some of this water quickly recycles back to the atmosphere through evaporation or transpiration. Transpiration This is the process by which plants release water vapor into the air through their leaves. The rest of the water in the soil slowly trickles down through gaps and pores in rocks. Groundwater This is water located within the gaps and pores in rocks below Earths surface. The solid surface of the Earth is called the lithosphere. Here, groundwater can collect in large underground lakes called aquifers. Earths Water Supply Did you know? The human body is made up of 60-75% water? You probably have 10 gallons of water inside you! Only about 3% of all water on Earth is fresh water. The other 97% is salt water. of Earths fresh water cannot be consumed by people. It is frozen in ice caps/glaciers near the Earths poles. The rest of the Earths water is groundwater. To get at it, we must dig wells and pump the water to the surface. How does fresh water stay fresh? The water cycle constantly moves ocean water to the land and back. When water evaporates from the ocean, the minerals (salt) is left behind. The water vapor that joins the other gases in the air is made of fresh water. When this water condenses again, fresh water forms. This fresh water fills our lakes and streams and becomes groundwater for us to enjoy. The fresh water eventually runs downstream into the ocean where it become salt water once again.