The National Wildlife Federation

Donate Donate
}

Water

Seasonal Water Sources

Vernal pools are a type of wetlands - sometimes resembling larger puddles. The pools go by a variety of names: prairie potholes, whale wallows, hog wallows, sinks, and kettles. They fill small basins at the base of trees or or in natural depressions in the landscape with rainwater or snow melt. They are not connected to any other water source.

When trees are without leaves in winter and early spring, the groundwater remains uncollected by the tree roots and stays at the surface and collects in pools. Dead leaves attract insects, which can be food for salamanders and other amphibians, and offer hiding places from predators.

These seasonal bodies of water show up in the spring (vernal is derived from the Latin word for spring) and disappear by summer. While their fleeting presence is often overlooked, they play a critical role in the ecology of many forests and prairies by sheltering species, including declining amphibians.

Vernal pools are important because they offer wildlife, such as salamanders, cricket frogs and other amphibians, a place to lay their eggs where they won’t be eaten by fish. These pools are fishless because they do not retain water year-round.

Many vernal pools are on private lands and many have been lost to development and drought.

Tips for maintaining vernal pools:

  • Do not fill areas of natural depression and let the areas dry up naturally. Since these pools will become dry by summer, mosquitoes do not have warm enough water to lay eggs in.
  • Leave trees, brush, dead logs in place, which can attract many types of wildlife.
  • Do not dump or dig into a pool, which can affect the area’s ability to hold water.
  • Leave space around a vernal pool, at a minimum a 100 foot natural buffer to maintain the habitat and food supply for its residents.