1. Hydric Soil Overview
All information is based upon current deliberations and recommendations of the National Technical Committee for Hydric Soils (NTCHS)
The NTCHS consists of members from NRCS, COE, EPA, FWS, BLM, FS, & 6 Universities
Current (4/2000) NTCHS membership.
Chair: Berman Hudson, NRCS(NSSC)
Members:
Wade Hurt, NRCS - NSSC
Michael Whited, NRCS (Wetland Science Inst.)
Neil Peterson, NRCS (Idaho)
Bobby Ward, NRCS (So-Central Region)
Lenore Vasilas, NRCS-COE, Baltimore
Russ Theriot, COE WES, Vicksburg
Buck Reed, FWS NWI, St. Petersburg, FL
Bill Sipple, EPA, Washington, DC
Jerry Daigle, FS, Atlanta, GA
Bill Volk, BLM, Billings, MT
Mike Vepraskas, NCSU, Raleigh, NC
Wayne Skaggs, NCSU, Raleigh, NC
Steve Faulkner, LSU, Baton Rouge, LA
Herb Huddleston, OSU, Corvallis, OR
Jimmie Richardson, NDSU, Fargo, ND
Richard Griffin, Prairie View A & M
Chien-Lu Ping, U of Alaska, Fairbanks
M. Whited - 4/2000

2. Objectives
Define terms used and describe procedures specified by the official hydric soil definition and criteria.
Explain difference between definition, criteria, field indicators, and technical standard.
Explain controversial or ambiguous aspects.
M. Whited - 4/2000

3. Introduction
Hydric soils are usually identified because wetlands are being delineated for government regulation.
They may also be identified for wetland restoration programs, CRP, etc
Hydric Soil identification is a process that involves both policy and science
“hydric soils are discrete boundaries on a natural continuum”
“jurisdictional wetlands are a psychological construct”
This short section introduces the concept of a hydric soil and associated terminology
For a soil scientist to be asked to place a flag on a hydric soil / non-hydric soil boundary goes against everything we know about landscape and soil evolution. However, it is necessary for the regulated public to have something scientific to grasp. Hydric soils can be an important piece of the puzzle.
Jurisdictional wetlands are something made up by people. What defines a wetland, water at 12” or less, why not 14” or less? Who says a hydric soil has to be dominantly gray below the A horizon? What about “brown” floodplain soils that function as wetlands for wildlife, flood control, etc? There is a difference between what may be an ecologically functional wetland and a jurisdictional wetland because jurisdictional wetlands are a psychological construct.
This psychological construct has come about from scientists, the regulated public, and the courts. Presently, although many people disagree over how to regulate wetlands, most people are in agreement on wetland identification.
M. Whited - 4/2000

4. Hydric Soils M. Whited - 4/2000
All hydric soils must meet the definition.
There are several ways to approach and / or verify the definition.
M. Whited - 4/2000

5. Definition
“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” (59 Fed. Reg , 7/13/94)
M. Whited - 4/2000

6. Anaerobic Waterlogging process Technical Definition Measurement
Microbes use up O2
H2O retards oxygen diffusion to soil
Technical Definition
Free of all O2
Depleted enough to stress plants
Measurement
O2 meters, Pt electrodes, or a, a’ dipyridyl
Problems
Difficult to measure O2, climate patterns, Reduction is “lower” than anaerobiosis
The definition of anaerobic for hydric soils is the “virtual” lack of oxygen. Almost no soil will become completely devoid of oxygen.
We use soil morphology, mostly based on the reduction of Iron, to identify hydric soils. Iron is reduced much “lower” on the redox scale than Oxygen.
M. Whited - 4/2000

7. “long enough” “the upper part”
Don’t know exactly how long
as little as 2 days in a lab
possibly in as little as 1 week in the field
The upper part is
the major portion of the rooting zone
usually 6 (sandy soils) to 12 inches (loamy soils)
M. Whited - 4/2000

8. “formed under conditions of”
Artificial drainage does not alter hydric soil soil status
however, it can alter soil properties
less OM
compaction
shift microbial populations
change pH and salinity
M. Whited - 4/2000

9. Growing Season Above biological zero in upper part Rough estimate
5 C, 41 F
Rough estimate
soil temp. regimes
More accurate
first frost free dates in soil survey report
WETS Table
M. Whited - 4/2000

10. Criteria The criteria for Hydric Soils (Fed. Reg., 2/24/95)
1 All Histels except Folistels and Histosols except Folists
2 The “saturation” criteria
3 Soils that are frequently ponded for long or very long duration during the growing season
4 Soils that are frequently flooded for long or very long duration during the growing season
Histels except Folistels added in 1999.
M. Whited - 4/2000

11. “Saturation” criteria
2 Soils in Aquic suborders, great groups, or subgroups, Albolls suborder, Aquisalids, Pachic subgroups, or Cumulic subgroups that are:
a. swp drained with water table = 0.0 ft. during growing season
b. pd or vpd and have either
(1) water table = 0.0 ft. during growing season if all textures within 20 inches are fine sand or coarser
(2) water table 0.5 ft. during growing season if perm.  6.0 in./hr. in all layers w/in 20”
(3) water table 1.0 ft. during growing season if perm. < 6.0 in./hr. in any layer w/in 20”
M. Whited - 4/2000

12. Criteria Main purpose is to create hydric soil lists.
Not all soils on list are hydric,
If any portion of the range of estimated properties for a soil is within the criteria that soil appears on the hydric list. For example, if a soil w/ perm. < 6 in./hr. has an estimated water table of 1 to 2 ft. during any portion of the growing season, that soil would be on the hydric list, even though most of the range in estimated water table is outside the criteria.
Hydric list is an interpretative rating which must be confirmed by on-site investigations
M. Whited - 4/2000

13. Criteria, cont. Criteria are not intended for on-site application
Criteria 1 is an indicator
Data that proves criteria 3 or 4 exists can be used to document the presence of a hydric soil
M. Whited - 4/2000

14. Hydric Soil Indicators
Indicators are not intended to replace or relieve the requirements contained in the Hydric Soil Definition
Indicators are used to identify the hydric soil component of wetlands; however, there are some hydric soils that lack one of the currently listed indicators
The indicators are “test positive” the lack of an indicator is not “test negative”
M. Whited - 4/2000

15. Draft Data Standard for Hydric Soils Requirements
Water table measurements
Redox potential measurements
Reduced Iron (Fe II) measurements
In-situ pH measurements
On-site precipitation data
Replicates
M. Whited - 4/2000

16. Summary All hydric soils must meet the definition
Criteria are used to generate lists
Lists are used off-site to determine if an area is likely or not to contain hydric soils
Indicators are used to identify hydric soils on site
Technical standard is used with data
To prove a hydric soil exists in the absence of an indicator, and to develop new indicators
M. Whited - 4/2000

17. Want to know more? Publications Training
NTCHS Interagency Field Indicators
Vepraskas - “Redoximorphic Features”
SSSA, Vepraskas and Sprecher - “Aquic Conditions and Hydric Soils: The Problem Soils”
Tiner - “Wetland Indicators”, CRC Press, May 99
Vepraskas and Richardson - “Wetland Soils”, Fall 2000
Training
Interagency Hydric Soils for Wetland Delineation
NRCS Advanced Hydric Soils
NRCS CD-ROM, “Hydric Soils Interactive”
M. Whited - 4/2000

18. WWW Sites http://www.pwrc.usgs.gov/wli/
NRCS Wetland Science Inst.
NRCS/NTCHS hydric soils homepage
Consulting soil scientists, lots of links
SWS, lots of wetland links
Mid-Atlantic hydric soils committee
UMinn, Hydric Soils Interactive CD on-line
M. Whited - 4/2000