We know how much shallow karst topography increases the likelihood that surface applied contaminants, including liquid manure, will find their way into the groundwater supply . The Kewaunee County Land and Water Conservation Department, however, uses the map shown below to get an even clearer picture of the potential for groundwater contamination in the county. The susceptibility ratings used to create this map are based on 7 soil characteristics affecting contamination susceptibility, shallow bedrock being one of those factors.
- soil texture of the surface layer
- soil texture of the subsoil layer
- organic matter content of the soil
- pH of the soil
- depth of the soil to bedrock or groundwater
- permeability of the soil
- drainage class of the soil
They caution, however, that this is a general planning tool. Areas that are located directly on a boundary line between two rating colors should be considered “either/or” a particular rating.
The problem for all of us, regardless of where we live in the county, is that all of our potable water comes from three underground aquifers. These sources include the unconsolidated surficial materials deposited by glacial ice, the Silurian dolomite aquifer, and the St . Peter and Cambrian sandstone aquifer. The depth to the water table varies throughout the county from less than 10 feet to over 30 feet . (Source: 2011 Kewaunee River Watershed Water Quality Update published by the Wisconsin Department of Natural Resources and UW Extension) http://dnr.wi.gov/org/water/condition/wtplans/TK03_WTPLAN.pdf