University of Wisconsin - Extension

STEVENS POINT, Wis.—Groundwater is vital to all of us living in Wisconsin, and the coming of spring represents an important time for our groundwater resources and anyone who relies on well water for their drinking water supply, says Kevin Masarik, University of Wisconsin-Extension Groundwater Education Specialist.

While all groundwater originates as precipitation, melting snow and spring rains generally provide the largest contribution of groundwater recharge to our aquifers each year. Because recharge during this time can occur rapidly, there is an increased risk of bacterial contamination of wells. This is especially true for wells located in karst regions, areas where soil layers are thin or absent and bedrock is highly fractured. Some well owners may actually notice their well water change appearance or odor after large rain events or snowmelts.

Coliform bacteria tests are an easy way to determine whether your water supply is bacteriologically safe to drink. Coliform bacteria are common in soils and are not generally considered harmful to health; however, they are also found in human and animal waste. For this reason, coliform bacteria are used as an indication of the sanitary condition of a water supply. A sanitary water supply or properly constructed well should not contain any coliform bacteria; its presence in well water indicates a pathway for other potentially dangerous pathogens such as E. coli, a type of fecal coliform, to enter the water supply.

If pathogens are in fact present, a variety of intestinal illnesses could occur from drinking the water. Private well owners should be testing their well water annually for coliform bacteria, or any time there is a sudden change in color, odor or taste.

In addition to coliform bacteria, there are a number of other contaminants that should be tested for. Some of these include human-related contaminants such as nitrate and pesticides if these are used or stored nearby, or naturally occurring contaminants such as arsenic.

While most private wells in Wisconsin provide safe drinking water, it is always a good idea to understand the quality of your drinking water. Anyone with questions concerning private well water quality or water testing is encouraged to contact their county health department or local UW-Extension office.