There are 20 major aquifers in the U.S., each with its own unique geologic characteristics. Since groundwater moves so slowly, any contaminants that filter down also move along at a slow rate, creating a pollution plume. Hydrogeologists have learned to track groundwater pollution plumes using geology maps and monitoring wells. The groundwater supply is recharged by precipitation that falls on the land. Groundwater is brought up to the surface by drilling a hole into an aquifer and pumping the water out.
Rural residents are responsible for testing their own well water for potential contaminants.
The City of Madison operates 23 municipal wells that pump out 30 million gallons of groundwater per day to nearly 200,00 Madison residents, according to Dennis Cawley, Senior Civil Engineer at Madison's Water Utility. The wells penetrate the aquifer to an average 800 feet of Cambian sandstone bedrock. Urban residents on city water must put their trust in state and federal water quality regulations. Yet, it's clear that trust is not shared by all, as is evidenced by the 2 billion-dollar a year bottled water industry. When surface water is polluted, an offensive odor, discolored water, or dead animal often alerts us that something has gone awry.