Geography of water

Minnesota’s Groundwater. MN Groundwater Provinces: Minnesota has 6 groundwater provinces determined by the two distinct types of bedrock and the availability of deposits above the bedrock. Groundwater and aquifer resources in each province are unique to that province.

Groundwater Province 1

Groundwater province 1, called the Metro Province, includes all or part of the following counties: Hennepin, Ramsey, Anoka, Wright, Washington, Chisago, Isanti, Dakota, Sherburne, Kannabec, Pine and Carlton.

The geology of the Metro Province consists of very old sandstone, limestone and dolostone bedrock overlain by over 100 feet of sandstone. Sandstone and limestone hold groundwater within the pore spaces of the rock and transmit water through fractures within the rock. Sandstone and limestone have a large capacity to hold water.

Contaminants in this area will come from industrial wastes, agricultural run-off in rural farmlands and urban run-off in the Twin Cities and their suburbs. In fact, Washington County is affected by the chemical pollutants generated by 3M at their Oakdale and Woodbury Disposal sites and the Cottage Grove facility and the Washington County landfill. MNWOO encourages all owners of private water wells to get your water tested and take advantage of the settlement reached between 3M and the State of Minnesota. Go to https://www.pca.state.mn.us/waste/3m-and-pfcs-2018-settlement. Common agricultural contaminants include nitrate and pesticides.

A few locations within the Metro Province may be experiencing, or will experience in the future, a limited supply of groundwater. This happens when the amount of water being pumped out of the aquifer exceeds the natural rate of replenishment in the aquifer. This can be caused by an increase in agriculture or an increase in population. This means that your well may supply less water than it previously has or, unfortunately, that the water table may fall below your well depth, rendering your well dry. These very events happened with White Bear Lake. A Ramsey County judge ruled that the Minnesota Department of Natural Resources violated the Minnesota Environmental Rights Act and caused a continuing decline the water levels in the underlying aquifers by allowing and mismanaging groundwater pumping, and thus failed to protect White Bear Lake. The Minnesota Court of Appeals, however, reversed that decision and the White Bear Lake Restoration Association may appeal to the Minnesota Supreme Court.

MNWOO wants to thank the Minnesota Geological Survey for their generous gift of the 54 county geologic atlas, state maps, and groundwater posters that we use in our well testing clinics and our presentations. Thank you

 

Groundwater Province 3

Groundwater Province 3, in southeast Minnesota, consists of labyrinthine conduits carved by water running through sandstone and limestone. This type of geology is called karst and it allows for an abundance of groundwater.

Groundwater Province 6

Groundwater Province 6, in northeast Minnesota, has ancient basalt bedrock risen to the surface, transmitting water only through fractures.

The other provinces tend to vary between these two extremes.

This is a map of the aquifers, the groundwater regions, of Minnesota. Note the green areas that indicate pollution; the dark green are Groundwater Management Areas designated by the Minnesota Department of Natural Resources to limit water use because of pollution and water quality issues whereas the lighter green are areas of increasing awareness of the extent of pollution. Map from the Minnesota Department of Natural Resources, https://www.dnr.state.mn.us/gwmp/areas.html

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