An impermeable layer below the water table that retards the flow of water.
Geological formation that may contain groundwater but significant quantities of water will not move through it under normal conditions. May function as a confining layer.
A geologic formation that is not permeable enough to yield significant quantities of water to wells, but on a regional scale can contribute significant water to the underlying or overlaying aquifers.
("aquiclude") - Geological formations or strata that have the ability to store water but can only transmit water in very small quantities (eg. silt, siltstone).
Sediment or rock that does not transmit water easily and therefore retards the motion of the water.
a barrier to the flow of groundwater in an aquifer
The less permeable beds in a stratigraphic sequence; beds may be permeable enough to transmit water in quantities that are significant in the study of regional groundwater flow or environmental contamination, but their permeability is not sufficient to allow completion of production wells within them.
a bed of low permeability adjacent to an aquifer; may serve as a storage unit for groundwater although it does not yield water readily
a body of rock that retards flow (e
a geologic unit exhibiting characteristics that generally retard the flow of groundwater ( e
An underground confining unit characterized by low permeability that does not readily permit water to pass through it despite the fact that it stores large quantities of water. The most common aquitards are clays, shales, and dense crystalline rocks.
a low-permeability layer of rock or clay that can store water but transmits it very slowly from aquifer to another.
A layer of geologic material that has low permeability and thus allows water to move through it slowly.
A subsurface semi-confining layer that can store ground water and also transmit it slowly from one aquifer to another.
A body of poorly permeable rock that is capable of slowly absorbing water from, and releasing water to, an aquifer, It does not transmit groundwater rapidly enough to directly supply a borehole or spring
underground geological formation that is slightly permeable and yields inappreciable amounts of water when compared to an aquifer List of Glossary Terms
A geologic formation that is saturated but is incapable of transmitting sufficient quantities of water to a well. However, this type of formation is capable of transmitting enough water to be considered as a significant part of the regional ground water system.
a geologic formation that may contain groundwater but is not capable of transmitting significant quantities of groundwater under normal hydraulic gradients. In some situations aquitards may function as confining beds.
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 confining bed that retards but does not prevent the flow of water from an adjacent aquifer.
Aquitard - A geologic formation or stratum that retards water movement significantly. It has a permeability of zero.
Geological formation that may contain groundwater but is not capable of transmitting significant quantities of it under normal hydraulic gradients. May function as confining bed.
A bed of almost impermeable material that retards, but does not prevent the movement of groundwater to or from an adjacent aquifer.
An underground bed or layer of soil, rock or clay that is too dense to allow easy passage of water.
An underground, saturated zone of low permeable rock, sand, or gravel that will not provide significant quantities of water to a well or spring.
Slowly permeable stratum that retards water movement into and out of adjacent or underlying aquifers . See: confining unit
Geologic formation/s of low hydraulic conductivity, typically saturated, but yielding a limited amount of water to wells. Also referred to as a confining unit.
low permeability rock layer that slows down the passage of groundwater
A part of a geologic formation (or one or more geologic formations) that is of much lower permeability than an aquifer and will not transmit water at a rate sufficient to feed a spring or for economic extraction by a well.
An aquitard is a zone within the earth that restricts the flow of groundwater from one aquifer to another. An aquitard can sometimes, if completely impermeable, be called an aquiclude or aquifuge. Aquitards are composed of layers of either clay or non-porous rock with low hydraulic conductivity.