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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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