SI-2C (11/02/04 version)
Environmental Targets And Priorities, Stream Integrity, Stream/Watershed Components: Wetlands


Approximately 90% of original Ohio wetlands have been eliminated by drainage and development. Aside from serving as vital habitat for amphibians and other wildlife, riparian wetlands play an important role in controlling floodwaters, recharging ground water, and capturing and processing nonpoint source pollutants.

Within the context of NPS management, the status and functionality of streamside/floodplain and/or river mouth wetlands are the focus. Water velocity slows in a wetland situation, causing pollutants, particularly sediments and nutrients, to settle out. When the wetlands are absent, larger loadings of these pollutants enter streams and rivers. The settling of these pollutants in the stream (versus in a wetland) can cause filling in of the interstitial spaces of the benthic substrate, leading to an "impaired" response in the macroinvertebrate community. The pollutants that do not settle, in or near the point of discharge into the stream, move downstream into Lake Erie or the Ohio River. It is generally believed that the loss of riparian wetlands throughout the Mississippi River basin is a contributing factor to Gulf Coast hypoxia.

For purposes of protecting water quality, Ohio EPA defines wetlands as locations where the water table is at, near, or above the land surface long enough each year to support the growth of water dependent vegetation and to result in the formation of characteristic wet soil types. Specifically, wetlands are those areas that are inundated or saturated by surface or ground water at a frequency and duration that are sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. "Wetlands" includes swamps, marshes, bogs, and similar areas that are delineated in accordance with the 1987 United States Army Corps of Engineers wetland delineation manual and any other procedures and requirements adopted by the United States Army Corps of Engineers for delineating wetlands.

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Assessing Wetland Integrity

In 1996 Ohio EPA began development of tools to determine the beneficial use status of Ohio wetlands. In1998, the State of Ohio established wetland water quality standards. Specifically, narrative criteria (PDF 7kb) have been codified to protect the functional and recreational aspects of a designated wetland.

Numeric biological criteria are anticipated in the future. These criteria will establish benchmarks for attainment of a likely tiered, ecoregion-specific wetland use system. The ecological integrity of a particular wetland will be evaluated using vascular plants, macroinvertebrates, and amphibians.

With hundreds of thousands of potential wetlands to be evaluated, methods to accurately characterize the status of an assessment unit, which may include large numbers of designated wetlands, are being considered. A probabilistic evaluation of wetland quality in several watershed assessment units has been initiated. To date, 286 individual wetlands have been evaluated using bio-assessment tools. Attainment status of wetlands will be determined subsequent to further advances in wetland water quality standards.