Workshop reviews groundwater report for Dodge County

Dodge County’s groundwater was the subject of a public workshop last week hosted by the Minnesota Department of Natural Resources (DNR).
The DNR is preparing county groundwater atlases for each of Minnesota’s 87 counties. The entire project includes a Geologic Atlas prepared by the University of Minnesota and a Groundwater Atlas for each county. The Geologic Atlas for Dodge County was completed in 2019 with the Groundwater Atlas released in 2024, said Scott Pearson of the DNR. Completion of the Geologic Atlas, he said, was necessary before the Groundwater Atlas could be completed.
The Groundwater Atlas uses maps, figures, tables, plates and text to describe hydrogeology of the county.
The report describes Dodge County as mostly agricultural land with minor forested areas found primarily along stream corridors. Average temperature in the summer is 68 degrees Fahrenheit and a winter annual temperature of 17 degrees Fahrenheit. Average annual precipitation for the county is 36 inches.
Dodge County, he said, has three surface watersheds — the Zumbro River, Cedar River and Root River. The Zumbro River watershed is the largest one of the three.
The report addresses a variety of water issues including water chemistry, pollution sensitivity, aquifer characteristics and groundwater usage.
Pollution sensitivity is determined by the time required for a contaminant to travel vertically from the surface to the water table, a buried aquifer or the bedrock surface.
While most of the county is rated as low when it comes to the pollution sensitivity, approximately 19 percent of the county has karst hydrology which means there is an extremely rapid contaminant travel. Pollution sensitivity, the report says, is highest in the east and northeast portions of the county where the depth to bedrock is less than 50 feet.
Domestic wells are the most common type of well and these rarely require a permit. Large volume users are those that withdraw more than 10,000 gallons a day or more than one million gallons per year. These users do require a permit.
The study shows that these large volume users have increased three-fold since 1988 with municipal water supplies the largest use, followed by ethanol production and livestock watering. In 2021, the report says these three made up of about 79 percent of permitted groundwater use.
Surface waters and groundwaters in the county are replenished solely by precipitation and surface water flow and groundwater levels fluctuate with wet and dry years.
Climate records from 1895 through 2022 show that average annual temperatures have increased by 2.0 degrees Fahrenheit, a number less than the statewide average temperature increase of 2.9 degrees. Annual precipitation has increased by 7.6 inches since 1895 and intense rainfall events producing daily totals over 1, 2 and 3 inches have been more common since 1990 than during any other period on record.
Climate projections indicate Dodge County is predicted to warm by an additional 2 to 4 degrees by 2050 and annual precipitation is predicted to increase by an additional one to three inches.
Geology and Groundwater Atlases have been completed for 36 Minnesota Counties. The atlases are in progress for 12 counties, including Steele County, while 37 counties have not yet been started.
Copies of the Groundwater Atlas are available online from the Department of Natural Resources website and printed copies can also be purchased online.