MGWA - Education
Water Facts

Glossary of Terms
This material is from The Groundwater Foundation

  • Aeration zone: (also known as the unsaturated zone) the zone above the water table is known as the aeration zone.
  • Artesian aquifer: see confined aquifer
  • Aquifer: An underground geological formation able to store and yield water.
  • Capillary water: Just above the water table, in the aeration zone, is capillary water that moves upward from the water table by capillary action. This water can move slowly and in any direction. While most plants rely upon moisture from precipitation that is present in the unsaturated zone, their roots may also tap into capillary water or into the underlying saturated zone.
  • Collection site: A stream, lake, reservoir, or other body of water fed by water drained from a watershed.
  • Condensation: The process in the hydrologic cycle by which a vapor becomes a liquid; the opposite of evaporation.
  • Confined Aquifer: (also known as artesian or pressure aquifers) exist where the groundwater is bounded between layers of impermeable substances like clay or dense rock. When tapped by a well, water in confined aquifers is forced up, sometimes above the soil surface. This is how a flowing artesian well is formed.
  • Conservation: The use of water-saving methods to reduce the amount of water needed for homes, lawns, farming, and industry, and thus increasing water supplies for optimum long-term economic and social benefits.
  • Consumptive use: The use of a resource that reduces the supply (removing water from a source like a river or lake without returning an equal amount). Examples include the intake of water by plants, humans, and other animals and the incorporation of water into the products of industrial or food processing.
  • Contaminant: Any substance that when added to water (or another substance) makes it impure and unfit for consumption or use.
  • Depletion: The loss of water from surface water reservoirs or groundwater aquifers at a rate greater than that of recharge.
  • Diffusion: The movement of a substance from an area of high concentration to an area of low concentration.
  • Discharge: An outflow of water from a stream, pipe, groundwater aquifer, or watershed; the opposite of recharge.
  • Drought: An extended period with little or no precipitation; often affects crop production and availability of water supplies.
  • Erosion: The wearing down or washing away of the soil and land surface by the action of water, wind, or ice.
  • Evaporation: The conversion of a liquid (water) into a vapor (a gaseous state) usually through the application of heat energy during the hydrologic cycle; the opposite of condensation.
  • Evapotranspiration: The loss water from the soil through both evaporation and transpiration from plants.
  • Fresh water: Water with less than 0.5 parts per thousand dissolved salts.
  • Gas (gaseous): see vapor
  • Ground water: Water found in the spaces between soil particles and cracks in rocks underground (located in the saturation zone). Groundwater is a natural resource that is used for drinking, recreation, industry, and growing crops.
  • Hydrologic cycle: (also known as the water cycle) The paths water takes through its various states--vapor, liquid, solid--as it moves throughout the ocean, atmosphere, groundwater, streams, etc.
  • Impermeable layer: A layer of material (clay) in an aquifer through which water does not pass.
  • Irrigation: The controlled application of water to cropland, hay fields, and/or pasture to supplement that supplied by nature.
  • Liquid: The part of the hydrologic cycle in which molecules move freely among themselves but do not separate like those in a vapor/gaseous state.
  • Municipal water system: A network of pipes, pumps, and storage and treatment facilities designed to deliver potable water to homes, schools, businesses, and other users in a city or town and to remove and treat waste materials.
  • Nonpoint source pollution: Wide-spread overland runoff containing pollutants; the contamination does not originate from one specific location, and pollution discharges over a wide land area.
  • Permeable: Capable of transmitting water (porous rock, sediment, or soil).
  • Permeable layer: A layer of porous material (rock, soil, unconsolidated sediment); in an aquifer, the layer through which water freely passes as it moves through the ground.
  • Plume: A continuous emission from a point source of contamination that has a starting point and a noticeable pathway.
  • Point source pollution: Pollutants discharged from any identifiable point, including pipes, ditches, channels, sewers, tunnels, and containers of various types.
  • Pollution: An alteration in the character or quality of the environment, or any of its components, that renders it less suited for certain uses. The alteration of the physical, chemical, or biological properties of water by the introduction of any substance that renders the water harmful to use.
  • Precipitation: The part of the hydrologic cycle when water falls, in a liquid or solid state, from the atmosphere to Earth (rain, snow, sleet).
  • Recharge: Groundwater supplies are replenished, or recharged, when water enters the saturation zone by actions like rain or snow melt.
  • Ridge lines: Points of higher ground that separate two adjacent streams or watersheds; also known as divides.
  • Runoff: Precipitation that flows over land to surface streams, rivers, and lakes.
  • Salinization: The condition in which the salt content of soil accumulates over time to above normal levels; occurs in some parts of the world where water containing high salt concentration evaporates from fields irrigated with standing water.
  • Salt marsh: A low coastal grassland frequently inundated by the tide.
  • Salt water: Water that contains a relatively high percentage (over 0.5 parts per thousand) of salt minerals.
  • Saturation zone: The portion below the earth's surface that is saturated with water is called the zone of saturation. The upper surface of this zone, open to atmospheric pressure, is known as the water table.
  • Soil: The top layer of the Earth's surface, containing unconsolidated rock and mineral particles mixed with organic material.
  • Storm drain: Constructed opening in a road system through which runoff from the road surface flows into an underground system.
  • Sublimation: The transition of a substance from the solid phase directly to the vapor phase, or vice versa, without passing through an intermediate liquid phase.
  • Substrate: A layer of material beneath the surface soil.
  • Surface water: Water above the surface of the land, including lakes, rivers, streams, ponds, floodwater, and runoff.
  • Temporary wetland: A type of wetland in which water is present for only part of the year, usually during the wet or rainy seasons; also known as vernal pools.
  • Transpiration: The process by which water absorbed by plants (usually through the roots) is evaporated into the atmosphere from the plant surface (principally from the leaves).
  • Unconfined aquifer: An aquifer in which the upper boundary is the water table.
  • Vapor: The state of water in the hydrologic cycle in which individual molecules are highly energized and move about freely; also known as gas/gaseous.
  • Wastewater: Water that contains unwanted materials from homes, businesses, and industries; a mixture of water and dissolved or suspended substances.
  • Wastewater treatment: Any of the mechanical or chemical processes used to modify the quality of wastewater in order to make it more compatible or acceptable to humans and the environment.
  • Water (H2O): An odorless, tasteless, colorless liquid made up of a combination of hydrogen and oxygen. Water forms streams, lakes, and seas, and is a major constituent of all living matter.
  • Water-bearing rocks: Several types of rocks can hold water, including: sedimentary deposits (sand and gravel), channels in carbonate rocks (limestone), lava tubes or cooling fractures in igneous rocks, and fractures in hard rocks.
  • Water cycle: See hydrologic cycle.
  • Water quality: The chemical, physical, and biological characteristics of water with respect to its suitability for a particular use.
  • Water quality standard: Recommended or enforceable maximum contaminant levels of chemicals or materials (such as chlorobenzene, nitrate, iron, arsenic) in water. These levels are established for water used by municipalities, industries, agriculture, and recreationists.
  • Watershed: The land area from which surface runoff drains into a stream, channel, lake, reservoir, or other body of water; also called a drainage basin.
  • Water table: The top of an unconfined aquifer; indicates the level below which soil and rock are saturated with water.
  • Water treatment plant: A facilities that treats water to remove contaminants so it can be safely used.
  • Well field: An area in which productive wells are drilled (similar to an oil field).
  • Wetland: Lands where water saturation is the dominant factor in determining the nature of soil development and the types of plant and animal communities. Other common names for wetlands are sloughs, ponds, and marshes.

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