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.

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.

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.