The system containing all the solid and liquid water on Earth.

Water from a sea or ocean that has an average salinity of 35 ppt (parts per trillion).

Water that has less than 0.2% salt content dissolved in it.

Water that fills lakes, streams, and other above land sources (water that can be seen).

Water that is stored in cracks and pores beneath Earth’s surface.

Water that flows over Earth’s surface. It comes from rain, melting snow or ice, or any water that does not soak into the soil or evaporate.

An area of land that drains runoff into a particular stream, lake, ocean, or other body of water.

The boundaries of a watershed at the highest points of land that surround it.

A body of water that flows within a channel - any naturally flowing channel of water.

A large body of water that forms in a basin surrounded by land and filled by runoff and precipitation.

An area of land that is saturated with water for part or all of the year that are too shallow to form lakes.

Large masses of moving ice that form on land and cover about 10% of the Earth’s surface (near north and south poles and on mountaintops).

A glacier that spreads over land in all directions is called an ice sheet. Ice sheets cover large areas of land and store enormous amounts of freshwater.

Ice that forms when seawater freezes - as seawater freezes, salt is left behind in the ocean.

Spaces or cracks between grains in rocks and soils.

The upper limit of the saturated zone - the upper surface of the aquifer.

An area of permeable sediment or rock that holds significant amounts of water.

The measure of the ability of fluid to move through a porous material.

Occurs where a water table rises to Earth’s surface.

The contamination of the environment with substances that are harmful to life.

The process of a body of water becoming nutrient-rich, but not in a good way. Excess nutrients from fertilizers or sewage can enter a stream and result in an increase in the population of algae (nitrogen and phosphorus). When the algae die, bacteria break down the algae and use oxygen as they decay. If decay rates are too high, oxygen levels in the water can be so low that fish and other animals cannot survive.

The open space between particles of rock or sediment.

Includes one or more oceans and other interconnected bodies of water and their interactions with the rest of the hydrosphere, the atmosphere, the geosphere, and the biosphere.

A large volume of sea water flowing in a certain direction.

A large circular system of ocean currents.

The vertical movement of water toward the ocean’s surface.

An area of ocean or large lake where there is not enough oxygen to support marine life.

The loss of color in corals that occurs when stressed corals expel the colorful algae that live in them.

The process of removing dissolved oxygen from a liquid (water).