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Introduction
Hydric Soils Criteria
Hydric Soils Lists
NTCHS Members
Hydric Soils Technical Notes
Procedure for Submitting Comments
Minutes from Annual Business Meetings
NTCHS Bylaws
 

Introduction

The NRCS oversees the development and application of criteria to identify hydric soils in consultation with the National Technical Committee for Hydric Soils (NTCHS). The NTCHS is made up of a standing membership of a chairperson who is an NRCS soil scientist with national responsibilities; four NRCS soil scientists; one member each from the U.S. Environmental Protection Agency, U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, U.S. Forest Service, and Bureau of Land Management; and at least five scientists, generally university professors, who serve as subject matter experts representing disciplines doing research in hydric soils.

The NTCHS is responsible for—

• Providing continuing technical leadership in the formulation, evaluation, and application of the hydric soil definition, criteria, indicators, and glossary.
• Updating and distributing the National List of Hydric Soils each year.
• Publishing and maintaining “Field Indicators of Hydric Soils in the United States.”
• Responding to public comment regarding suggested changes in the hydric soil definition, criteria, indicators, glossary, and lists.
• Using technical methodologies and standards to determine soil, hydrologic, and climatic data necessary to define and identify hydric soils more accurately.

Definition of a Hydric Soil

A hydric soil is defined as 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. Most hydric soils exhibit characteristic morphologies that result from repeated periods of saturation or inundation that last more than a few days.

Field Indicators of Hydric Soils

Field indicators of hydric soils are documented soil characteristics that are associated only with hydric soils. Field indicators are an efficient onsite means to confirm the presence of a hydric soil because they help identify soils that meet the hydric soil definition without further data collection. Some hydric soils do not yet have documented field indicators. Hydric soils that do not have documented field indicators require evidence to prove that the soil meets the definition of a hydric soil. Additional field indicators are under development and are being tested.

The publication "Field Indicators of Hydric Soils in the United States" includes the indicators of hydric soils approved by the NRCS and the NTCHS for use in identifying, delineating, and verifying hydric soils in the field.

Hydric Soils Concept

The concept of hydric soils includes soils developed under sufficiently wet conditions to support the growth and regeneration of hydrophytic vegetation. 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. Some soils that are designated as hydric have phases that are not hydric because of water table, flooding, or ponding characteristics.

Hydric Soils Lists

Hydric soils lists are compilations of all map units with either a major or minor component that is at least in part hydric. The lists are available as a full national list and by state using the State Soil Data Access Hydric Soils List web report and by soil survey area using the Soil Data Access Hydric Soils List web report. These lists could include components that are soil series, components that are classified at categories higher than the series level in soil taxonomy, and miscellaneous land types.

The lists are useful in identifying map units that may include hydric soils. Because the lists includes both major and minor (small) percentages for map units, in some cases, most of the map unit may not be hydric. Also, some components may be phases of soil series that have a range of characteristics that both meet and do not meet hydric indicator requirements; therefore, only a portion of that component's concept (or range in characteristics) may in fact be hydric. 

Hydric soils lists have a number of agricultural and nonagricultural uses. These include assistance in land-use planning, conservation planning, assessment of potential wildlife habitat, and identification of wetlands. The NRCS is responsible for developing database selection criteria, maintaining official lists, and implementing procedures to identify and list hydric soils. These criteria and approved lists of potential hydric soil map unit components are developed in consultation with the NTCHS. The lists of hydric soils are created by using National Soil Information System (NASIS) database selection criteria. 

Hydric Soils Criteria

New NASIS Database Selection Criteria

The NTCHS has updated the hydric criteria that NASIS uses to select map unit components for the hydric soils list. These new criteria are recorded in Federal Register Document 2026-05787, which was filed on March 25, 2026. The updated criteria will add soil components that represent subaqueous landforms to the hydric soils list. The updates reflect refinements in knowledge of the soils of the United States as subaqueous soils are now mapped in previously unmapped areas. These soils have always met the hydric soil definition, whether identified by the criteria or not, and thus represent an insignificant change in acreage of hydric soils. The criteria now include Wassents, a new subaqueous taxonomic suborder.

The updated criteria are as follows:

1. All Histels except Folistels, all Histosols except Folists, and all Wassents; or
    
2. Map unit components in Aquic suborders, great groups, or subgroups, Albolls suborder, Historthels great group, Histoturbels great group, or Andic, Cumulic, Pachic, or Vitrandic subgroups that:
   1. Based on the range of characteristics for the soil series, will at least in part meet the requirements of one or more field indicators of hydric soils in the United States, or
   2. Show evidence that the soil meets the definition of a hydric soil; or
       
3. Map unit components that are frequently ponded for long duration or very long duration during the growing season that:
   1. Based on the range of characteristics for the soil series, will at least in part meet the requirements of one or more field indicators of hydric soils in the United States, or
   2. Show evidence that the soil meets the definition of a hydric soil; or
       
4. Map unit components that are frequently flooded for long duration or very long duration during the growing season that:
   1. Based on the range of characteristics for the soil series, will at least in part meet the requirements of one or more field indicators of hydric soils in the United States, or
   2. Show evidence that the soils meet the definition of a hydric soil.

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 high tides, or any combination of sources.

Frequently flooded, ponded, saturated is 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.

Hydric Soils Technical Notes

The Hydric Soils Technical Standard

The hydric soil technical standard (HSTS) was developed by the NTCHS to provide a scientifically based and standardized approach to document soils that are saturated long enough during the growing season to become anaerobic, thus demonstrating that the definition of a hydric soil has been met. The field indicators for hydric soils, developed for the purpose of bypassing the requirement of deploying the HSTS to every situation where a hydric soil determination is needed, do not provide a field indicator solution to every hydric circumstance known to exist in the United States. 

Berkowitz et. al. (2021) provide the methodology for investigators to employ the HSTS to their study sites to determine whether a soil that does not meet the requirements of a field indicator is in fact hydric. The utility of this methodology is clearly of use for conducting hydric determinations in areas where hydric soils exist but do not meet the requirements of a field indicator (problematic hydric soils), to test current field indicators for applicability in new locations, to test new proposed field indicator concepts, to conduct novel research in hydric soils, or any other situations where it is necessary to validate the presence of hydric and nonhydric soils.

View the guide to the HSTS in full below.

Hydric Soils of Problematic Conditions and Altered Materials

“Hydric Soils of Problematic Conditions and Altered Materials: A Working Compendium of Contemporary Scenarios and Solutions” addresses the challenges that soil scientists encounter in conducting field determinations for hydric soils. It provides a resource for soil scientists across the United States to reference information on problematic hydric soils and access guidance to address problematic scenarios. The hope is that access to an organized framework will encourage and stimulate innovations that will continue to generate further solutions for hydric soil problems. 

Hydric Soils Technical References

The following references provide further guidance on the HSTS and its implementation.

Berkowitz, J. F., and Griffin, R. W. (2025). Identifying hydric soils using a,a'-dipyridyl dye (ERDC/EL TN-25-5). U.S. Army Engineer Research and Development Center. https://dx.doi.org/10.21079/11681/49932
 

Berkowitz, J. F., VanZomeren, C. M., Currie, S. J., and Lenore Vasilas, L. (2017). Application of α, α’-dipyridyl dye for hydric soil identification.” Soil Science Society of America Journal, 81(3), 654–658. https://doi.org/10.2136/sssaj2016.12.0431
 

Berkowitz, J. F., Vepraskas, M.F., Vaughan, K. L., and Vasilas, L. M. (2021). Development and application of the hydric soil technical standard. Soil Science Society of America Journal, 85(3), 469–487. https://doi.org/10.1002/saj2.20202
 

Sprecher, S. W. (2008). Installing monitoring wells in soils (ver. 1.0). USDA, Natural Resources Conservation Service.
 

Vepraskas, M. J., and Sprecher, S. W. (1997). Overview of aquic conditions and hydric soils. In M. J. Vepraskas and S. W. Sprecher (Eds.), Aquic conditions and hydric soils: The problem soils (SSSA Special Publication 50, pp. 1–22). Soil Science Society of America. https://doi.org/10.2136/sssaspecpub50.c1

Procedure for Submitting Comments

Hydric Soils List or Criteria

If you have comments on the criteria for hydric soils or believe soils should be removed from or added to the hydric soils list, gather supporting data to make your case and either submit the documentation and the proposed changes in the criteria along with your supporting data to Cory Owens, Chair, NTCHS, or to your NRCS State Office with copies to Cory Owens.

Supporting documentation must include information on the geographic area (soil survey area) and hydrology, vegetation, and soil characteristics that support changing the definition of the soil series. A written response will be given to inquiries within a reasonable time.

Field Indicators

Guidelines for requesting changes to field indicators are as follows:

1. To propose a new indicator or revision to an existing indicator, the following documentation is required as a minimum to accompany all requests for additions and changes to existing hydric soil indicators for consideration into future versions of the “Field Indicators of Hydric Soils in the United States”: 
   1. Detailed descriptions of at least three pedons that document the addition or change and detailed descriptions of the neighboring nonhydric pedons.
   2. Detailed vegetative documentation recording the specific plant community at each of the six pedon locations summarizing any contrasting patterns between the proposed upland and hydric positions.
   3. Saturation/inundation data and oxidation-reduction potential (Eh) data for a duration that captures the saturation cycle (dry-wet-dry) of at least one of the hydric pedons and one of the nonhydric pedons. Precipitation and in-situ soil-water pH data from the same sites should also be provided (fig. 5). Data are to be collected according to the Hydric Soil Technical Standard (Berkowitz et al., 2021). 
       
2. To add or delete a test indicator, the following documentation is required to accompany all requests for adding or deleting a test indicator in “Field Indicators of Hydric Soils in the United States”: 
   1.  Detailed descriptions of at least three hydric pedons that document the test indicator and detailed descriptions of three neighboring nonhydric pedons.
   2. Detailed vegetative documentation recording the specific plant community at each of the six pedon locations, summarizing any contrasting patterns between the proposed upland and hydric positions.
   3. All requests involving a and b above require a short written description that identifies the problem, explains the rationale for the request, and provides the following: 
      • A person responsible and point of contact (email and postal addresses and phone number)
      • A timeline for supporting data and final report to be delivered to NTCHS
      • A timeline requested for final NTCHS decision and partners involved in the project
      • Requests, plans, and data should be sent to the current Chair of the NTCHS.

Requests, plans, and data should be sent to Cory Owens, Chair, NTCHS.

Minutes from Annual Business Meetings

These minutes include the deliberations of the NTCHS.

NTCHS Bylaws