MONROE— Groundwater is the principal water supply for Green County municipalities, industries and rural residents. While municipal water supplies are regularly monitored and required to meet drinking water standards, private well owners must make decisions regarding when and what to test for and what to do if there is a problem.
In an effort to understand changes to well water quality over time and help to focus public health outreach efforts to private well owners, Green County undertook steps to initiate a 5-year project to monitor well water quality.
In July 2019, Green County began collaborating with the UW-Stevens Point and UW-Madison Division of Extension’s Center for Watershed Science and Education to test a subset of Green County private wells. The following county departments are assisting with the project: Extension Green County, Green County Health Department, Green County Land and Water Conservation Department, Green County Land Information Office and Green County Land Use and Zoning Department.
Criteria were developed and used to select wells that are representative of Green County’s diverse soils, geology, land use and well construction. Nearly 800 landowners were contacted in 2019 with the goal of creating a long-term monitoring network of wells, whose owners would submit well samples annually for five years. A total of 342 landowners submitted samples for Year 1 of the project; while 310 samples were received in Year 2. The goal is for a minimum of 240 wells to be tested in all five years of the project.
All water samples were analyzed for nitrate-nitrogen, chloride, pH, alkalinity, total hardness and conductivity at the state-certified Water and Environmental Analysis Lab. The results of Year 2 confirm Green County’s groundwater to be slightly basic, hard water, with high alkalinity. These characteristics are often associated with scaling and treatment such as water softeners may be commonly used to counteract these effects. These aesthetic characteristics of the water are largely influenced by the geologic materials groundwater is stored and transported in; lower values of pH, alkalinity, and total hardness are sometimes found in wells near the Sugar River where wells may be shallower and access the sand/gravel aquifer versus bedrock.
Nitrate is a common health-related contaminant found in Green County’s groundwater (average = 5.7 mg/L nitrate-nitrogen). Levels less than 10 mg/L are considered suitable for drinking. Eighteen percent of wells tested higher than the 10 mg/L drinking water standard. Infants and women who are or may become pregnant should not drink water higher than 10 mg/L nitrate-nitrogen; all other persons should avoid long-term consumption at these levels. Approximately 73% of wells tested had nitrate levels higher than 2 mg/L. Because less than 2 mg/L nitrate-nitrogen are generally considered natural or background, levels above this threshold indicate groundwater that has been impacted by land use. Sources of nitrate include nitrogen fertilizers; animal waste or other bio-solids and septic system drain fields.
Chloride provides additional insight into the effects of land use on water quality. Background levels of chloride in groundwater are typically less than 10 mg/L. Sources of chloride include potash fertilizers or certain bio-solids applied to agricultural fields, road salt, and septic system drain fields. Sixty-two percent of wells measured chloride greater than 10 mg/L; the average chloride concentration in Green County was 18.6 mg/L. There are no health effects associated with chloride.
Participating landowners will be mailed sample kits for Year 3 of the project starting in Oct.; data from the project will continue to be analyzed as each year’s testing is completed. Data collection in Years 3 through 5 will allow researchers to better understand how widely well water quality fluctuates from year to year, what factors help explain water quality, and whether well water quality is getting better, worse, or staying the same with respect to human-induced impacts such as nitrate and chloride.
More information about the results, including this year’s report, recorded educational session and link to an interactive dashboard further investigating results are available online at www.green.extension.wisc.edu.
For any questions, contact Kevin Masarik, Groundwater Education Specialist at 715-346-4276 or kmasarik@uwsp.edu, Joe Bonnell, Natural Resources Educator at 608-930-9850 or joe.bonnell@wisc.edu or Victoria Solomon, Community Resource Development Educator at 608-328-9440 or victoria.solomon@wisc.edu.
