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Hydric Soils
Wetland PhotoThe definition of a hydric soil is a soil that formed under conditions of saturation, flooding or ponding long enough during the growing season to develop anaerobic conditions in the upper part. Soils that are sufficiently wet because of artificial measures are included in the concept of hydric soils. Also, soils in which the hydrology has been artificially modified are hydric if the soil, in an unaltered state, was hydric.

Undrained hydric soils that have natural vegetation should support a dominant population of ecological wetland plant species. Hydric soils that have been converted to other uses should be capable of being restored to wetlands.

Criteria that identify soil properties unique to hydric soils have been established. These criteria are used to identify map unit components that normally are associated with wetlands.

Source: USDA NRCS

The Hydric Soils in Blue Earth County can be viewed in this PDF document.  A map of the hydric soils can be viewed in this PDF map.  In addition, the Web Soil Survey is an interactive web map that allows users to display hydric soils and many other attributes and properties of soils.


Glossary of Terms Used in Hydric Soils Criteria

Anaerobic means a situation in which molecular oxygen is virtually absent from the environment.

Artificial hydric soil means a soil that meets the definition of a hydric soil as a result of an artificially induced hydrologic regime and did not meet the definition before the artificial measures were applied.

Drained means a condition in which ground or surface water has been removed by artificial means.

Flooded means a condition in which the soil surface is temporarily covered with flowing water from any source, such as streams overflowing their banks, runoff from adjacent or surrounding slopes, inflow from the high tides, or any combination of sources.

Frequently flooded, ponded, saturated: a frequency class in which flooding, ponding, or saturation is likely to occur often under usual weather conditions (more than 50 percent chance in any year, or more than 50 times in 100 years).

Hydric soil means a soil that formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part. This definition includes soils that developed under anaerobic conditions in the upper part but no longer experience these conditions due to hydrologic alteration such as those hydric soils that have been artificially drained or protected (e.g., ditches or levees).

Long duration means a duration class in which inundation for a single event ranges from 7 days to 1 month.

Map unit means a collection of areas defined and named the same in terms of their soil components or miscellaneous areas or both.

Map unit components means the collection of soils and miscellaneous areas found within a map unit.

Phase, map unit means a subdivision of a map unit based on features that affect its use and management (e.g., slope, surface texture, stoniness, and thickness).

Ponded means a condition in which water stands in a closed depression. The water is removed only by percolation, evaporation, or transpiration.

Very long duration means a duration class in which inundation for a single event is greater than 1 month.