Groundwater Glossary
Index
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Acre-foot - The volume of water which would cover an area of one acre
to a depth of one foot. It is equal to 43,500 cubic feet or 325,851 gallons.
Activated carbon - A granular material usually produced by the roasting of
cellulose base substances, such as wood or coconut shells,
in the absence of air. It has very porous structure and is used
in water conditioning as an adsorbent for organic matter and certain dissolved
gases.
Aquifer
- An underground
layer of rock, sand, or gravel that contains water in sufficient
quantities to supply a well.
Aquitard - An underground,
saturated zone of low permeable rock, sand, or gravel that will
not provide significant quantities of water to a well or spring.
Artesian well - A well
that penetrates a confined aquifer. The water level in these wells
rises above the upper surface of the aquifer due to the pressure
in the confined aquifer. If the water pressure is great enough,
the well will overflow.
Condensation
- The process
whereby water is changed from a gas (water vapor) into a liquid.
Cone of depression - The
cone-shaped area around a well where the groundwater level is
lowered by pumping. The shape of the cone is influenced by the
underground porosity and water yield of the well.
Confined aquifer - Aquifers
that are wedged between layers of relatively impermeable materials
and are consequently under pressure. Also know as an artesian
aquifer.
Contaminant - Any physical,
chemical, biological, or radiological substance or matter in the
water.
Discharge area - The area
or zone where ground water emerges from the aquifer. The outflow
maybe into a stream, lake, spring, wetland, etc.
Evaporation - The process
whereby water is changed from a liquid to a gas (water vapor).
Groundwater - Water beneath
the surface of the earth which saturates the pores and fractures
of sand, gravel, and rock formations.
Hardness - A characteristic
of water caused by the presence of various salts, calcium, magnesium,
and iron. Water is soft if the content of these materials is low,
hard if the content is high.
Hydrologic cycle - The
continuous circulation of water between the earth and the atmosphere,
involving condensation, precipitation, runoff, percolation, evaporation,
and transpiration.
Non-point source of pollution
- Contaminates found in water from a source that cannot be specifically
defined. For example contamination resulting from municipal runoff
or agricultural infiltration.
Perched water - Unconfined
groundwater held above the water table by a layer of impermeable
rock or sediment
Percolate - The downward
flow of water through the pores or spaces of unsaturated rock
or soil
Permeability - The capacity of rock or soil to transmit
water.
pH - A numerical measure
of acidity and alkalinity. The scale is from 1 to 14; neutral
is pH 7.0, values below 7.0 are increasingly acidic, and above
7.0 are increasingly alkaline (basic).
Plume - A flowing body
of contaminated groundwater that extends from the source of contamination
to another point in the direction of the groundwater flow.
Point source of pollution
- Contaminants found in water that can be readily identified from
a specific source such as a leaking underground storage tank.
Pollution - Any substance,
natural or synthetic, that degrades water quality to such a degree
that water is not suitable for a particular use
Porosity - The degree
to which the total volume of soil or rock is permeated with spaces
or cavities through which water or air can move.
Potable water - Water
which is free from impurities that may cause disease or harmful
physiological effects, such that the water is safe for human consumption.
Potentiometric surface
- An imaginary surface formed by measuring the level to which
water will rise in wells of a particular aquifer. For an unconfined
aquifer the potentiometric surface is the water table; for a confined
aquifer it is the static level of water in the wells. (Also known
as the piezometric surface.)
ppb (parts per billion)
- A ratio used to describe the proportion of one substance to
another. In terms of time, l ppb is equal to one second in 32
years.
Recharge areas - Areas
of land that allow groundwater to be replenished through infiltration
or seepage from precipitation or surface runoff.
Salinity - The concentration
of dissolved salts in water. The most desirable drinking water
contains 500 ppm or less of dissolved minerals.
Saturated zone - The portion
of subsurface soil and rock where every available space is filled
with water. Aquifers are located in this zone.
Surface water - Bodies
of water, snow, or ice on the surface of the earth (such as lakes,
streams, ponds, wetlands, etc.).
Transpiration - The process
by which plants give off water vapor into the atmosphere.
Turbidity - A measure
of water cloudiness caused by the amount of suspended matter in
the water
Unconfined aquifer - An
aquifer which the water table as its upper boundary. Because the
aquifer is not under pressure the water level in a well is the
same as the water table outside the well. An unconfined aquifer
is near to the earth's surface causing it to be easily recharged
as well as contaminated
Unsaturated zone - An
area, usually between the land surface and the water table, where
the openings or pores in the soil contain both air and water
Watershed - All land and
water within a drainage area, defined by topographic high points.
Water table - The top
of an unconfined aquifer where water pressure is equal to atmospheric
pressure. The water table depth fluctuates with climate conditions
on the land surface above and is usually gently curved and follows
a subdued version of the land surface topography.
Well - An opening in the
surface of the earth for the purpose of removing fresh water.
This fact sheet was produced by the
University of Michigan - Flint,
Regional Groundwater Center.
