The average depth of a water well is 100 to 200 feet. While 9.8 feet is the lowest recommended depth, some wells can go as deep as 3,000 feet.
While the depth of water wells vary greatly, it is important that the well is drilled deeper than the elevation of the underground water table. Because levels will fluctuate all throughout the year, as well as from year to year, a well needs to be deep enough to accommodate water in drought conditions. Shallow wells are also more susceptible to contamination than those that are deeper. Wells have been used since prehistoric times and were important in the creation and civilization of many towns. Wells were even used by Eratosthenes to help calculate the radius of the Earth in 230 BC.