Not all underground wells are artesian wells. Some underground wells are shallow wells . Artesian wells are located in lower, confined aquifers . Water enters the aquifer from the highest level of the aquifer, and when a well is drilled at a lower level, pressure from above forces the water out through the artesian well. Most domestic wells are shallow wells, located in unconfined aquifers .
Water levels rise and fall according to the amount of rainfall in the area.
Shallow wells are more easily contaminated because they are less protected from things such as oil spills, chemical pollutants . Underground water from confined aquifers is more uniform in temperature, taste and quality. It is less subject to pollution because there is a barrier of nonporous material protecting it. The following words or phrases appeared in the above section in Italic, bold type. Here are brief descriptions for them.