| Term | Definition |
|---|---|
| freshwater | water that has less than 0.2 percent salt dissolved in it |
| alpine glacier | a glacier that forms in the mountains and is on every continent except Australia. |
| ice sheet | a glacier that spreads over land in all directions |
| sea ice | ice that forms when seawater freezes |
| ice cores | long columns of ice taken from glaciers |
| runoff | water that flows over Earth’s surface |
| stream | a body of water that flows within a channel |
| watershed | an area of land that drains runoff into a particular stream, lake, ocean or other body of water |
| estuary | a coastal area where freshwater from rivers and streams mixes with salt water from seas or oceans |
| lake | a large body of water that forms in a basin surrounded by land |
| groundwater | water that lies below ground |
| water table | the upper limit of the saturated zone |
| porosity | the measure of a rock’s ability to hold water |
| permeability | measure of water’s ability to flow through rock and sediment |
| aquifer | an area of permeable sediment or rock that holds significant amount of water |
| wetland | an area of land that is saturated with water for part or all of the year |
