| A | B |
|---|
| aquifer | Any underground layer of rock or sediment that holds water. |
| eutrophication | The process by which nutrients in a lake build up over time and cause an increase in the growth of algae. |
| divide | A ridge of land that separates one watershed from another. |
| hollow | A small valley or a stream bed that has been deepened and holds standing water. |
| impermeable | A characteristic of materials, such as clay and granite, through which water does no easily pass. |
| permeable | A characteristic of materials through which water easily passes. |
| recharge | New water that enters the aquifer from the surface |
| saturated zone | The area of permeable rock or soil in which the cracks and pores are totally filled with water. |
| tributary | A stream or smaller river that feeds into a main river |
| unsaturated zone | The layer or rocks and soil above the water table in which the pores contain air as well as water. |
| watershed | The land area that supplies water to a river system. |
| water table | The top of a saturated zone, or depth to the ground water under the Earth's surface. |
