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WETLAND
HYDROLOGY
Wetland hydrology is the second wetland parameter. The term wetland
hydrology encompasses, "all hydrological characteristics of areas
that are periodically inundated or have soils saturated to the surface
at some time during the growing season. Areas with evident characteristics
of wetland hydrology are those where the presence of water has an overriding
influence on characteristics of vegetation and soils due to anaerobic
and reducing conditions respectively," (U.S. Army Corps of Engineers 1987).
Hydrology is usually the least exact of the three parameters. Indicators
of wetland hydrology are sometimes difficult to find in the field. It
is, however, "essential to establish that a wetland area is periodically
inundated or has saturated soils during the growing season," if an accurate
wetland determination and/or delineation is going to be made (U.S. Army
Corps of Engineers 1987).
One
detail that must be stressed concerning wetland hydrology is that an area
does not have to be wet year-round to be considered a wetland. Some areas
may contain moisture for several weeks or months out of every year, or
they may stay dry for years on end. Seasonal wetlands such as bottomland
hardwood swamps undergo a fairly regular wet/dry cycle. Temporary wetlands,
such as prairie potholes, can have wet/dry cycles that are irregular from
year to year. Even when these areas are dry they still perform very important
functions and must be considered wetlands (Rude 1992).
When
the soil is visibly saturated or inundated with water, the presence of
a wetland hydrologic regime can be relatively easy to discern. When the
area does not exhibit standing water, however, identifying wetland hydrologic
conditions becomes more difficult. Still, even when the presence of water
is sporadic, hidden, or currently absent, an individual can find several
signs that the area is a functioning wetland. Listed below are some of
these more subtle indicators:
- soft,
mushy, waterlogged ground;
- water
marks on trees or other erect objects;
- thin
layers of sediment deposited on leaves or other objects;
- drift
lines-small piles of debris lodged in trees or piled against other
objects and oriented in the direction of water movement through an
area;
- visible
mud or dried mud cracks in low-lying places (U.S.
Department of Commerce and U.S. Army Corps of Engineers 1987).
This
list of wetland hydrology indicators is only intended to provide an individual
with some general indications that an area may have a wetland hydrologic
regime. When making legal determinations and/or delineations, federal
and state entities use more technical criteria than just these to discern
the presence of a wetland hydrology. Among the more technical criteria
are very specific definitions of when the growing season is determined
to occur, when an area is considered saturated, and the period of time
an area is required to be inundated or saturated before it can be considered
a wetland (U.S. Army Corps of Engineers 1987 and U.S. Department of Agriculture
1996).
[Introduction
| Delineation | Hydric Soils|Wetland
Hydrology| Hydrophytic Vegetation| Wetland
Classification |Summary]
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