The Minnesota Department of Natural Resources will collect water samples this summer from about 50 wells in Rock County for use in the county’s groundwater atlas. Some property owners will be contacted by mail or phone for permission to sample their wells. The process involves collecting a water sample from an outside location for laboratory analysis. Participation is voluntary and property owners will receive a report of the laboratory results.

Wells are selected based on geology, location, well depth and well construction. Data from participants’ wells will help the DNR create county maps and descriptions of groundwater distribution, movement, and conditions, and the pollution sensitivity of aquifers. The final products will be available as printed maps, reports and geographic information system (GIS) files available on the web.

The atlas can be used to help identify viable water sources, evaluate supply, identify recharge sources and flow, manage sustainability, guide decisions for well and septic system construction, assist in well-head protection for public water supply, and assess pollution sensitivity and likely contamination migration.

County atlases are produced in two parts over the course of several years. Part A covers the geology of the county, and is expected to be completed for Rock County in 2020 by the Minnesota Geological Survey. Part B will expand on this information to cover the hydrogeology (groundwater) using the new Rock County well sampling data. The DNR expects to complete Part B in 2022.

The county atlas program is funded in part by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources. Funding also comes from the Clean Water Fund, which receives 33 percent of the sales tax revenue from the Clean Water, Land and Legacy Amendment approved by voters in November 2008.

A full description of this DNR program and status reports for atlas products is available at mndnr.gov/groundwatermapping.