Earth’s Water

1. Earth’s Water • The Water Cycle • Almost all of the hydrosphere is saltwater found in oceans, seas, and some lakes. • The amount of water on Earth never changes, but it is constantly moving through the processes of evaporation, condensation, and precipitation. • Evaporation is when the sun’s energy causes water to change into vapor or gas. • Condensation is an excess of water vapor that changes into liquid water after warm air cools. • Precipitation is the release of moisture through rain, snow, or sleet.

3. Earth’s Water • Bodies of Salt Water • Seventy percent of the Earth’s surface is water, primarily salt water. • Salt water cannot be used for drinking, farming, or manufacturing. • Due to a growing population and the need for more freshwater, some countries are focusing on the desalination process, which removes the salt from seawater. • Desalination is expensive and is also controversial; critics believe the process has negative environmental and economic impacts.

4. Earth’s Water • Bodies of Freshwater • More than two-thirds of the world’s scarce freshwater is frozen in glaciers. • Less than one-third of a percent of freshwater is found in lakes, rivers, and streams and their tributaries. • Aquifers and groundwater are important sources of freshwater found underground within the Earth.