| A | B |
|---|
| ______ percent of water on earth is fresh water | 3 |
| ______ percent is salt water that is found in the oceans | 97 |
| water vapor | The invisible, gaseous form of water. |
| groundwater | Water that fills the cracks and pores in underground soil and rock layers. |
| water cycle | The continuous process by which water moves from Earth’s surface to the atmosphere and back, passing through the living and nonliving parts of the environment. |
| In the water cycle, water moves from bodies of water, land, and living things on Earth’s surface | to the atmosphere and back to Earth’s surface. |
| evaporation | The process by which molecules at the surface of a liquid, such as water, absorb enough energy to change to a gaseous state, such as water vapor. |
| transpiraion | The process by which plants release water vapor through their leaves |
| precipitation | Forms of water such as rain, snow, sleet, or hail that fall from clouds and reach Earth’s surface. |
| In addition to household purposes, people use water for | agriculture, industry, transportation, and recreation. |
| irrigation | The process of supplying water to areas of land to make them suitable for growing crops. |
| Water is essential for living things to | grow, reproduce, and carry out other important processes. |
| photosynthesis | The process by which plants use water, plus carbon dioxide and energy from the sun, to make food. |
| habitat | The place where an organism lives and that provides the things it needs to survive. |
| tributary | A stream that flows into a larger stream |
| A river and all its tributaries together make up a | river system |
| watershed | The land area that supplies water to a river system. |
| divide | A ridge of land that separates one drainage basin or watershed from another. |
| A flood occurs when | the volume of water in a river increases so much that the river overflows its channel. |
| levee | A long ridge formed by deposits of sediments alongside a river channel. |
| Ponds and lakes form when | water collects in hollows and low-lying areas of land. |
| reservoir | A natural or artificial lake that stores water for human use. |
| lake turnover | A seasonal change refreshes the supply of nutrients throughout the lake (water mixes, minerals, plant matter, and other nutrients rise from the lake bottom to the surface). |
| eutrophication | The process by which nutrients in a lake build up over time, causing an increase in the growth of algae. |
| About ____ percent of an iceberg lies below the surface. | ninty |
| pores | Tiny openings in and between particles of rock and soil that may contain air or water. |
| permeable | Characteristic of materials such as sand and gravel that allow water to pass easily through them. |
| impermeable | Characteristic of materials through which water does not easily pass, such as clay and granite. |
| saturated zone | A layer of permeable rock or soil in which the cracks and pores are completely filled with water. |
| water table | The top of the saturated zone, or depth to the groundwater in an aquifer. |
| unsaturated zone | A layer of rocks and soil above the water table in which the pores contain air as well as water. |
| aquifer | An underground layer of rock or soil that holds water. |
| spring | A place where groundwater bubbles or flows out of cracks in the rocks. |
| People can obtain groundwater from an aquifer by | drilling a well below the water table. |
| recharge | New water that enters an aquifer from the surface. |
| artesian well | A well in which water rises because of pressure within the aquifer. |
| wetland | An area of land that is covered with a shallow layer of water during some or all of the year. |
| wetlands provide | habitats for many living things, because of their sheltered waters and rich supply of nutrients. |
| Wetlands also help control floods by | absorbing extra runoff from heavy rains. |
