Aquifers

Groundwater is water that flows or seeps downward and saturates soil or rock, supplying springs and wells.
The beginning of a drought is difficult to determine. Several weeks, months, or even years may pass before people know that a drought is occurring. The end of a drought can occur as gradually as it began. Dry periods can last for 10 years or more.
The depth to the water table can change (rise or fall) depending on the time of year.
A well is said to have gone dry when water levels drop below a pump intake. This does not mean that a dry well will never have water in it again, as the water level may come back through time as recharge increases.
A confined aquifer is an aquifer below the land surface that is saturated with water.
An aquifer is a geologic formation that can store and transmit water to wells, springs and some streams.
Artesian well water is water from a well that taps an aquifer that is 'confined'. This aquifer is water-bearing rock below ground that is surrounded by other rock or material that does not allow water to pass through.
NAWQA findings indicate that MTBE is most frequently detected in ground water underlying urban areas in comparison to agricultural and mixed land-use settings. MTBE was detected in about 14 percent of wells sampled in urban areas.
Devils Hole is a tectonic cave developed in the discharge zone of a regional aquifer in south-central Nevada. The walls of this predominantly subaqueous cavern are coated with dense vein calcite.