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Well: a well whose use has been permanently discontinued, or
a well which is in such disrepair that its continued use for the
purpose of obtaining groundwater is impractical or may be a health
hazard. Such wells can be a direct "pipeline" for introducing
contamination into the groundwater.
A geologic formation which may contain water but does not transmit
System: A water-bearing layer(formation) of rock or sediment
capable of yielding sufficient, economical quantities of water to
wells. Typically is unconsolidated deposits or sandstone or limestone.
A saturated but poorly permeable formation that does not yield water
freely to a well or a spring. However, an aquitard may transmit
appreciable water to or from adjacent aquifers.
Area of influence:
Area surrounding a pumping or recharging well within which the water
table or potentiometric surface has been changed due to the well's
pumping or recharge. DIAGRAM
Conditions: In a confined aquifer, when the water level in a
well rises above the top of the aquifer.
Practices (BMPs): structural, nonstructural, and managerial
techniques recognized to be the most effective and practical means
to reduce surface water and groundwater contamination while still
allowing the productive use of resources.
Fringe: a zone in the soil just above the water table that remains
saturated or almost saturated, because the water is drawn up against
the force of gravity due to waters adhesive and cohesive forces
(capillary action). DIAGRAM
Cone of depression:
A depression in the groundwater table or potentiometric surface
that has the shape of an inverted cone and develops around a well
from which water is being withdrawn. The slopes of the cone become
increasingly steep the closer they are to the well. Its trace (perimeter)
on the land surface defines the zone of influence of a well. Also
called cone of drawdown. DIAGRAM
aquifer: Aquifers that are wedged between layers of relatively
impermeable materials and are consequently under pressure. Also
know as an artesian aquifer. DIAGRAM
Layer: geological material through which significant quantities
of water can not move; located below unconfined aquifers, above
and below confined aquifers. Also known as a confining bed.
An undesirable substance (physical, chemical, biological, or radiological)
not normally present, or an unusually high concentration of a naturally
occurring substance, in water, soil, or other environmental medium.
The vertical distance groundwater elevation is lowered, due to the
removal of groundwater. The distance between the static water level
and the surface of the cone of depression.
Well: When the top of a well in a confined aquifer is below
the potentiometric surface, water will flow out of the well under
Water occurring in the zone of saturation in an aquifer or soil.
Water beneath the surface of the earth which saturates the pores
and fractures of sand, gravel, and rock formations.
barrier: Rock or artificial material with a relatively low permeability
that occurs (or is placed) below ground surface, where it impedes
the movement of groundwater and thus may cause a pronounced difference
in the heads on opposite sides of the barrier. Also called a confining
Height of the column of water at a given point in a groundwater
system above a datum plane such as mean sea level. It is also a
measure of pressure as in a confined aquifer where the elevation
of the groundwater does not equal its head because it is under pressure.
Conductivity (K): A coefficient of proportionality describing
the rate at which water can move through a permeable medium. It
is a function of the porous medium and the fluid. The rate of flow
of water in gallons per day through a cross-section of one square
foot under a unit hydraulic gradient (gpd/ft²), at the prevailing
temperature. See permeability.
Cycle: The continuous circulation of water between the earth
and the atmosphere, through condensation, precipitation, runoff,
percolation, evaporation, transpiration, groundwater storage and
seepage, and re-evaporation into the atmosphere. DIAGRAM
Gradient (i): Slope of a water table or potentiometric surface.
Groundwater flows from points of high elevation and pressure to
points of low elevation and pressure. The difference in hydraulic
head divided by the distance along the flowpath.
Characteristic of geologic materials that limit their ability to
transmit significant quantities of water under the head differences
normally found in the subsurface environment.
Underground Storage Tank (LUST): An underground tank which has
a structural rupture and its contents are leaving their containment
and entering the surrounding environment.
source: Pollution of the water from numerous widespread locations
that are hard to identify and pin-point. Ex. agri-chemicals through
leaching or runoff or any conveyance not meeting the definition
of point source.
Aquifer: An aquifer containing unconfined (unpressurized) groundwater
held above a lower body of groundwater by an unsaturated zone; often
a result of clay lenses in the soil strata. DIAGRAM
Capacity of a rock or soil material to transmit a fluid. DIAGRAM
surface: See potentiometric surface. DIAGRAM
Pollution of water from one place in a concentrated manner that
is easy to identify. Ex. leaking underground storage tank, discharge
pipe from a sewage treatment plant, any pipe, ditch, channel, tunnel,
conduit, well, discrete fissure, container, rolling stock, animal
feeding operation, or landfill, from which pollutants are or may
Plume: an area of a stream or aquifer containing degraded water
resulting from migration of a pollutant. It extends from the source
of contamination to another point in the direction of the water
The capacity of soil or rock to hold water. The ratio of the volume
of void spaces in a rock or sediment to the total volume of the
rock or sediment. DIAGRAM
Suitable for human consumption as drinking water.
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.) DIAGRAM
System (PWS) (EPA): Any water system providing water for human
consumption for an average of at least 25 persons per day (or 15
or more service connections) and in use for at least 60 days each
year. Further defined as follows:
Water System: A Public Water System which serves at least
15 services connections used by year-round residents or regularly
serves at least 25 year-round residents.
Non-Community Water Systems: A Public Water System that is
not a community water system. These systems do not regularly serve
at least 25 of the same persons over six months per year.
Non-Community Water System: A Public Water System that is
not a community water system and that regularly serves at least
25 of the same persons over 6 months per year.
area: Area of land allowing water to pass through it into an
aquifer by surface infiltration. This process occurs naturally when
rainfall filters down through the soil or rock into an aquifer,
usually in the higher gradient section overlying the aquifer. DIAGRAM
Water Level: The level of water in a well that is not being
pumped. (The drawdown has been recharged by the surrounding groundwater.)
Zone: The portion of subsurface soil and rock where every available
space is filled with water. Aquifers are located in this zone. DIAGRAM
Time of Travel
(TOT): The time required for a particle of water to move in
the saturated zone from a specific point to a well. A line can be
drawn around the area for which groundwater is expected to reach
the well within a chosen period.
A measure of the ability of an aquifer to transmit water. The rate
at which water is transmitted through a unit width of an aquifer
under a unit hydraulic gradient. Transmissivity values are typically
given in gallons per day through a vertical section of an aquifer
one foot wide and extending the full saturated height of an aquifer
under a hydraulic gradient of 1 (gpd/ft).
Aquifer: An aquifer which the water table is 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. DIAGRAM
Storage Tank (UST): a tank system, including its piping, that
has at least 10% of its volume underground
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. Also called the zone of aeration. DIAGRAM
All the land area and water within the confines of a drainage divide
in which all surface runoff will drain through one point, such as
a stream or river. Determined by topographic high points.
The water level of an unconfined aquifer, below which the pore spaces
are saturated. 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. DIAGRAM
An opening in the surface of the earth for the purpose of removing
An area containing two or more wells supplying a public water supply
The physical structure, facility, or device at the land surface
from or through which groundwater flows or is pumped from subsurface,
Protection Area (WHPA): A geographically designated surface
and subsurface area surrounding a water well or wellfield, supplying
a Public Water System, through which contaminants are reasonably
likely to move toward and reach such water well or well field. This
is an area where groundwater protection is emphasized. A WHPA includes
at least the delineated capture zone area, but could be influenced
by other factors such as existing land use and zoning, site and
facility identification and location, political boundaries, natural
features, and environmentally sensitive areas.
Protection Program (WHPP): A program to protect public water
supply systems from potential sources of groundwater contamination.
Zone of Contribution
(ZOC): The area surrounding a well that encompasses all areas
and features that supply groundwater to the well. DIAGRAM
Zone of Influence
(ZOI): The area of groundwater which is affected by the pumping
of a well. The faster the pumping rate the larger the area. The
area of land above the cone of depression. DIAGRAM
Zone of Transport
(ZOT): The area that contains the groundwater that will reach
the well within a specified time. Similar to time of travel.
Wellhead Protection Program