Question

3) Draw or describe the structure of a confined and of an unconfined aquifer. Why are aquifers important?

Answer 1

A confined aquifer is an aquifer below the land surface that is saturated with water. Layers of impermeable material are both above and below the aquifer, causing it to be under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer.

A water-table--or unconfined--aquifer is an aquifer whose upper water surface (water table) is at atmospheric pressure, and thus is able to rise and fall. Water-table aquifers are usually closer to the Earth's surface than confined aquifers are, and as such are impacted by drought conditions sooner than confined aquifers.

Aquifers are geologic formations, a group of formations, or a part of a formation that contains enough saturated permeable material to result in significant quantities of water for wells and springs.

Deep aquifers like the Ogallala have long been water sources for irrigation. Many villages and even large cities draw their water supply from wells in aquifers. Municipal, irrigation, and industrial water supplies are provided through large wells. Multiple wells for one water supply source are called wellfields. Using ground water from deep, confined aquifers provides more protection from surface water contamination.

Aquifers that provide sustainable fresh groundwater to urban areas and for agricultural irrigation are typically close to the ground surface and can have some recharge of fresh water from rivers or precipitation that percolates into the aquifer.