What Makes a Groundwater Well Go Dry?
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 aquifer recharge from precipitation seepage increases or pumping of the aquifer is lessened.
It is true that all the water in the ground comes from infiltration of precipitation from above, but the geology of the underground rock determines the infiltration and movement characteristics of the water that is in the ground.
The water level in a well depends on a number of things:
.Depth of the well
.Type (confined or unconfined) of aquifer the well taps
.Amount and rate of pumping that occurs in the aquifer
.Permeability and porosity of the underground rock
.Amount of recharge occurring from precipitation or artificial recharge
.Well in unconfined water table aquifers is more directly influenced by the lack of rain than those in deeper confined aquifers. A deep well in a confined aquifer in an area with minimal pumping is less likely to go dry than a shallow, water-table well.
Groundwater, which is in aquifers below the surface of the Earth, is one of the most important natural resources. Groundwater is the source of about 33 percent of the water that city water departments public supply.
It provides drinking water for more than 90 percent of the rural population who do not get their water delivered to them from a city water department or private water company. Even some major cities rely solely on groundwater for all their needs.
About 42 percent of the water used for irrigation comes from groundwater. Withdrawals of groundwater are expected to rise as the population increases and available sites for surface reservoirs become more limited.
Groundwater is an especially important natural resource in those parts of the country that don’t have ample surface-water sources. It often takes more work and costs more to access groundwater as opposed to surface water, but where there is little water on the land surface; groundwater can supply the water needs of people.