| A | B |
|---|
| aquifer | Porous, water-saturated layers of sand, gravel, or bedrock that can yield an economically significant amount of water. |
| desalination | Purification of salt water or brackish (slightly salty) water by removal of dissolved salts. |
| drought | Condition in which an area does not get enough water because of lower-than-normal precipitation or higher-than-normal temperatures that increase evaporation. |
| evaporation | Conversion of a liquid into a gas. |
| floodplain | Flat valley floor next to a stream channel. For legal purposes, the term often applies to any low area that has the potential for flooding, including certain coastal areas. |
| groundwater | Water that sinks into the soil and is stored in slowly flowing and slowly renewed underground reservoirs called aquifers; underground water in the zone of saturation, below the water table. |
| natural recharge | Natural replenishment of an aquifer by precipitation, which percolates downward through soil and rock. |
| recharge area | Any area of land allowing water to pass through it and into an aquifer. See aquifer, natural recharge. |
| reliable runoff | Surface runoff of water that generally can be counted on as a stable source of water from year to year. |
| saltwater intrusion | Movement of salt water into freshwater aquifers in coastal and inland areas as groundwater is withdrawn faster than it is recharged by precipitation. |
| stream | Flowing body of surface water. Examples are creeks and rivers. |
| subsidence | Slow or rapid sinking of part of the earth's crust that is not slope-related. |
| surface runoff | Water flowing off the land into bodies of surface water. |
| surface water | Precipitation that does not infiltrate the ground or return to the atmosphere by evaporation or transpiration. |
| water table | Upper surface of the zone of saturation, in which all available pores in the soil and rock in the earth's crust are filled with water. |
| watershed (also called drainage basin) | Land area that delivers water, sediment, and dissolved substances via small streams to a major stream (river). |
| zone of aeration | Zone in soil that is not saturated with water and that lies above the water table. |
| zone of saturation | Area where all available pores in soil and rock in the earth's crust are filled by water. |
