- Pollution Sensitivity of the Bedrock Surface: HG-01
- Pollution Sensitivity of Near-Surface Materials: HG-02
- Water-Table Elevation and Depth to Water Table: HG-03
The Minnesota Hydrogeology Atlas (MHA) series was created to compile and update existing data developed by the County Geologic Atlas program.
The new atlases reflect current data and methods statewide, though some map layers will still contain legacy data that may not match the current standard product and methods.
It can be used to evaluate the distribution of groundwater in the state, for water appropriation applications, and to guide the sustainable use of groundwater. It will also assist in geophysical, karst and other hydrogeological investigations.
Refer to the County Atlas for associated reports and additional information.
Pollution Sensitivity of the Bedrock Surface: HG-01
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This compilation includes only the counties with existing pollution sensitivity maps for the bedrock surface and units. As future county atlas work continues, new counties will be added to this compilation.
The pollution sensitivity rating corresponds to estimated travel time through the glacial sediments burying the bedrock surface. as defined by the Geologic Sensitivity Workgroup (1991). The assumptions that relate the geologic factors to travel time were tested with chemistry data from groundwater samples (e.g., tritium age and carbon-14). For more information see the Definition of pollution sensitivity.
This statewide atlas for the pollution sensitivity of the bedrock surface respects the legacy of the previous maps, with minimal alterations made to the original product data. The county maps were created by various authors using different geologic factors. A unified rating code was applied for ease of use and visual continuity based on the current geological sensitivity rating for bedrock as defined by vertical travel time (Geologic Sensitivity Workgroup, 1991).
Pollution Sensitivity of Near-Surface Materials: HG-02
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The sensitivity to pollution of near-surface materials is an estimate of the time it takes for water to infiltrate the land surface to a depth of 10 feet. It is intended to estimate the time of travel through the unsaturated zone to reach the water table, which is assumed to be 10 feet below land surface everywhere for the purposes of this method. Sensitivity varies across Minnesota. Generally, areas of coarse-grained material are modeled as higher sensitivity to pollution compared to areas of fine-grained material. Exceptions exist where special conditions occur.
Water-Table Elevation and Depth to Water Table: HG-03
*To ensure the images in the report print correctly, select "Advanced > Print as Image" from the print dialog box.
This report, map, and digital data provide statewide groundwater information for the water-table elevation and depth to water table.
- Water-table elevation represents the elevation of the water table relative to sea level.
- Depth to water table represents the distance from the surface to the water table.
The water table is defined as the surface below which sediment is saturated with groundwater. It occurs in both aquifer and nonaquifer sediment across the entire state. In general, the water table is within 10 feet of the land surface and follows the surface topography. However, the water table can be more than 120 feet below land surface near deeply incised river valleys such as the St. Croix, Minnesota, and Mississippi river valleys.
Water-table elevation and depth to water table are considered in construction projects and land use programs. They provide data for evaluating the impact of potential pollutant sources on groundwater and are a component of surface-water infiltration planning. These maps provide guidance for all of these applications. However, additional site-specific information is required to make accurate determinations on a smaller scale.