What is the Water Cycle Water on Earth is being constantly recycled through a process called the water cycle This is the movement of water between Earth’s oceans atmosphere and land It has four main stages evaporation condensation precipitation and accumulation Evaporation Condensation Water vapor cools and changes from a gas into tiny liquid droplets in this stage of the water cycle We see this happen in the formation of clouds Water changes from its liquid state to a gas in this part of the water cycle Water evaporates from the oceans lakes rivers and even plants and becomes invisible water vapor in the air Evaporation page 8 Clouds page 14 Clouds contain large amounts of water 4 Water stores page 24
Precipitation As the tiny water droplets that make up clouds get bigger they eventually become so heavy that they escape the cloud and fall as rain If it’s cold enough for the droplets to freeze they fall as snow sleet or hail Rainfall page 18 Water drops fall as rain Accumulation Water that has fallen to the ground as rain sleet snow or hail soaks into the ground or runs over it It gathers in water stores such as lakes or aquifers No matter where it falls it eventually makes its way back to oceans lakes and rivers and the cycle begins again Water accumulates in rivers Transpiration page 11 River basins page 22 5
Our Blue Planet Viewed from outer space our planet is mostly a deep and dazzling blue This is because 71 percent of Earth’s surface is covered with water most of which is salt water in the oceans Watery planet Earth is the only planet in our solar system that has liquid water due to its exact distance away from the Sun If Earth was closer to the Sun it would be too hot and all the water would boil into gas Further away from the Sun it would be too cold and all the water would be frozen solid as ice Total volume Although 71 percent of Earth’s surface is covered in water the total volume of water is tiny compared to the size of our planet overall Salt water These dots represent the amount of water on Earth that is salt water and freshwater Freshwater 6
7 Life Water is essential for life on Earth The very first living things on the planet evolved in the water in the oceans Many creatures including humans rely on freshwater from rivers aquifers and lakes that is constantly replaced by the water cycle We use freshwater to drink wash and grow crops Agriculture makes up the majority of our freshwater use worldwide About 70 percent worldwide About 70 percent of the water that humans take out of rivers and groundwater goes toward agriculture Without freshwater we couldn't grow the food we need to live FACT FILE WHERE IS EARTH'S WATER FOUND 96 5 is in the oceans salt water 1 74 is in the ice caps and glaciers 1 7 is groundwater in the ground The remaining 0 06 includes all the water that is stored in other places including lakes rivers swamps in the atmosphere and biological water inside plants and animals The water on Earth is constantly recycled we don't lose or gain water from elsewhere in space That means water you drank today is the same water that the very first living things swam around in
