What makes a piece of land a wet-land? It may seem like an easy question when the word is broken down, but when we look closer, we find that not all wetlands are wet for the same reason. Hydrology (water characteristics) is the defining feature of a wetland, and the soil and plants in wetlands are shaped by the presence of water. The amount, flow, composition and source of water helps determine the soil type and vegetation found there. Contrary to their name, wetlands may not be wet all of the time. To help identify wetlands, let’s look at one of the largest factors of wetland hydrology—water source.
• Floodplain forests, lake and riverside marshes, tidal marshes and mangrove swamps receive water from surface flow. This means that there is active cycling of water and nutrients from visible water sources like a lake, river, or the ocean.
• Fens and seeps receive water from groundwater sources. This means that the water table and soil surface reach the same height. These wetlands can be fed by an underground water source and often contain high concentrations of nutrients that stimulate plant growth.
• Bogs, cypress domes and vernal pools receive most of their water from precipitation. This means that these wetlands are replenished by rainfall and snowmelt and have limited to no connection with other water sources.
Viewer Tip: Wetlands can be found all over the country and on every continent except Antarctica. Do you know of any wetlands in your area? See if you can tell what kind of water source your local wetland depends on. How might this determine the types of plants found there? Learn more about the different types of wetlands found in the United States.
Infographic also available in Spanish.
(Sources: Vance, Linda K. 2009. Geographically Isolated Wetlands and Intermittent/Ephemeral Streams in Montana: Extent, Distribution, and Function. Report to the Montana Department of Environmental Quality and the U.S. Environmental Protection Agency. Montana Natural Heritage Program, Helena, Montana 33 pp. EPA, “Nutrient Criteria Technical Guidance Manual: Wetlands,” http://www2.epa.gov/sites/production/files/documents/wetlands_chapter1-2.pdf)