An aquifer is
a water saturated permeable geologic layer, or fracture zone, that is able to
transmit significant quantities of water.
A geologic layer that cannot transmit significant quantities of water is
usually referred to as an aquiclude. An
aquitard is a rock unit that generally has a low permeability and hence will
transmit only very limited quantities of water and are generally not suitable
for production wells. The terms Aquifer
or aquitards can be used to define most geologic strata. The most common aquifers include permeable
sedimentary rocks such as sandstones, limestone’s, sand and gravel layers, and
highly fractured volcanic and crystalline rocks. Common aquitards are un-fractured shale’s,
clays and dense (un-fractured) crystalline rocks.
Sedimentary
aquifers form layers and usually have a large lateral extent, whereas aquifers
in fracture zones in igneous and crystalline rocks may have a very limited
lateral extent. When searching for water using any geophysical method,
including the Electro seismic method, the type of aquifer that may be present should
be considered, both when planning a ground water survey and especially when considering
drilling a well.
- Confined—An aquifer overlain by one or more layers of impermeable rock or soil that restrict water to within the aquifer. The water is confined under pressure. Drilling a well into a confined aquifer releases that pressure and causes the water to rise in the well. These wells are sometimes called artesian wells.
- Unconfined—An aquifer that is not overlain by a layer of impermeable rock or soil. Water in a well will naturally stay at the level of the water table. As water is removed from the well, the water table at that place is lowered, causing the surrounding ground water to flow toward the well.
Whether you are on a fractured rock aquifer, an artesian aquifer, a confined aquifer, an unconfined aquifer or have no groundwater at all, the benefits of a groundwater survey when planning a new well, far outweigh the costs of drilling a dry well.
Phone: 800-394-6207
Southwest Groundwater Surveyors serve California, Arizona, Nevada, New Mexico, and Utah.
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