A geologic formation through which virtually no water moves.

An underground layer of saturated sand, gravel, or rock that contains water in sufficient quantities to supply a well.

A test involving the withdrawal of measured quantities of water from a well and the measurement of resulting changes in head in the aquifer at various selected locations.

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.

A well that penetrates through or into an impermeable layer of silt, clay, or rock. 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 the top of the land surface or well (flowing artesian).

A general term for the consolidated (solid) rock that underlies soils or other unconsolidated surficial material.

The zone at the bottom of the vadose zone where groundwater is drawn upward by capillary force.

The surface and subsurface area surrounding a water well or wellfield which supplies a public water system, through which contaminants are reasonably likely to move toward and reach such water well or wellfield within a specified period of time.

The determination of the boundaries of the capture zone(s), typically delineated by complex computer groundwater flow programs, involving the input of numerous data, including water levels (heads), pumping volumes, aquifer thickness, transmissivities, recharge values and other aquifer characteristics.

The cone shaped area around a well where the groundwater level is lowered due to pumping. The shape of the cone is influenced by the underground porosity and water yield of the well.

Any physical, chemical, biological or radiological substance or matter that degrades water quality and/or threatens the safety of its intended use (i.e. drinking water). Some contaminants are only an aesthetic concern, while others are considered hazardous to your health.

The reduction of head at a point caused by the withdrawal of groundwater. In other words, the distance between the static water level and the surface of the cone of depression.

An imaginary contour line on the water table or potentiometric surface showing an equal pressure head of groundwater in an aquifer. Normally, water flow is toward these lines.

The combined loss of water from an area through transpiration of plants and evaporation from soil or water.

A general term for unconsolidated sediment transported by glaciers and deposited directly on land or in the sea.

Water beneath the surface of the earth, which saturates the pores and fractures of sand, gravel and rock formations.

The rate of flow of water in gallons per day through a cross-section of one square foot under a unit hydraulic gradient (gpd/ft squared), at the prevailing temperature. See permeability.

The science dealing with the interrelationships of geologic materials and processes with subsurface waters and related geologic aspects of surface waters.

The continuous circulation of water between the earth and the atmosphere, involving condensation, precipitation, runoff, percolation, evaporation and transpiration.

The study of the occurrence, distribution and chemistry of all waters of the earth.

The downward flow of water through the pores or spaces of unsaturated rock or soil.

A well drilled and installed in a selected location for the purpose of collecting information regarding aquifer characteristics, such as geologic material, hydraulic parameters, water levels and water quality.

Contaminants found in water from a source that cannot be specifically defined. For example, contamination resulting from agricultural infiltration or runoff.

The capacity of rock or soil to transmit water. See "hydraulic conductivity."

Contaminants found in water that can be readily identified from a specific source such as a leaking underground storage tank.

The spaces (voids) between particles of earth materials, such as clay, silt, sand, gravel, and rock. It is measured as the ratio of the volume of openings to the total given volume.

An imaginary surface representing the total head of groundwater in a confined aquifer, defined by the level to which water will rise in a well.

A ratio used to describe the proportion of one substance to another. In terms of time, 1 ppb is equal to one second in 32 years; also is equal to 1 drop in a 10,000-gallon tank. Also is measured as micrograms per Liter (ug/L).

A ratio used to describe the proportion of one substance to another. In terms of time, 1 ppm is equal to 1 minute in 2 years.

An area in which water reaches the zone of saturation from surface infiltration from precipitation, surface run-off, or groundwater underflow.

The portion of subsurface soil and rock where every available space is filled with water. Aquifers are located in this zone.

The level of water in a well that is not being affected by withdrawal of groundwater.

The volume of water an aquifer releases from or takes into storage per unit surface area of the aquifer per unit change in head.

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).

An aquifer with 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 usually near to the earth's surface causing it to be easily recharged - but contaminated as well.

An area, usually between the land surface and the water table, where the openings or pores in the soil contain both air and water.

The zone containing water under pressure less than that of the atmosphere, including soil water, intermediate vadose water, and capillary water. This zone is limited above by the land surface and below by the surface of the zone of saturation (water table).

All land and water within a drainage area, defined by topographic high points.

The top of an unconfined aquifer where water pressure is equal to atmospheric pressure; in other words, the surface between the zone of saturation and the zone of aeration. 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.