What are Shallow open-water wetlands? — Ducks Unlimited Canada Skip to main content
Wetlands

Shallow open-water wetlands

What is a shallow open-water wetland?

Open Water wetlands have water depths less than two metres, yet are too deep for emergent marsh vegetation to establish. Visually, these wetlands appear to be shallow lakes, although floating-leaved and submerged aquatic vegetation are common in more nutrient-rich settings.

Ecological benefits

  • Retain and store water helping to moderate flooding, recharge groundwater and maintain stream flows
  • Productive for many plants and animals in nutrient-rich environments

Types of Open Water wetlands

  • Open water: <25% aquatic vegetation on the water
  • Aquatic bed: >25% aquatic vegetation on the water
  • Mudflat: a temporary condition when water levels are low (drawdown)

Vegetation

  • Submerged aquatic (e.g. water-milfoil) and floating vegetation (e.g. pond lily)
  • Too deep for emergent plants like cattails and rushes to establish

Hydrology

  • Water sources include precipitation, run-off, groundwater and streams
  • Water levels are generally permanent but may fluctuate seasonally, exposing mudflats

Soil

  • Soil is poorly developed because of high water levels and lack of oxygen
  • Substrate: silt, gravel or combinations of organic deposits

Types of wetlands

Canada’s wetlands can be broadly categorized into two types: organic and mineral.

Organic wetlands

Otherwise known as peatlands, these wetlands have an abundance of peat accumulation on which organic soils (excluding Folisols) are developed. These types of wetlands can include swamps, marshes, or shallow open-water wetlands.

Bogs

Bogs

Bogs are peatlands that have deep deposits of poorly decomposed organic material (referred to as peat). They are elevated above the surrounding terrain and receive water and most nutrients from precipitation.

Fens

Fens

Fens are peatlands with deep organic deposits and are influenced by slow, lateral water movement. Often referred to as “muskeg,” fens are the most extensive wetlands in the western boreal forest.

Mineral wetlands

Mineral wetlands are found in locations where there is an excess of water on the surface and where there is little or no organic matter or peat due to geomorphic, hydrologic, biotic, edaphic (soil-related), or climatic causes. These wetlands are distinguished by gleysolic soils or peaty phases of these soils.

Marshes

Marshes

Marshes are wetlands periodically inundated by standing or slowly moving water and creating nutrient-rich soil.

Swamps

Swamps

Most commonly recognized as shoreline areas of streams, lakes and floodplains, swamps are either treed or shrubby.

Shallow open-water wetlands

Shallow open-water wetlands

Shallow open-water wetlands have water depths of less than two metres, yet are too deep for emergent marsh vegetation to establish.