Ephemeral Pools Appear in Washington Sagelands

Conservancy scientists were delighted to find this ephemeral pool at our Marcellus Preserve this spring.

It’s one of nature’s spring surprises: In eastern Washington and other parts of the Pacific Northwest, winter runoff is causing temporary pools of water known as "vernal pools" to appear.

These rare and special ecosystems can range from the size of a puddle to a shallow lake, but often remain dry for years at a time, only appearing after particularly wet conditions.

When they do fill with water, they provide home to a unique range of life, including many invertebrates that are able to remain dormant during the harsh, dry season. You’ll also find toads and salamanders in vernal pools, but perhaps their most well-known inhabitant is the fairy shrimp, a small crustacean named for its graceful movements.

Scientists were delighted to find an ephemeral pool at the Conservancy’s Marcellus preserve in eastern Washington this spring. They’ve rarely seen one full of water. "They only appear when there’s enough moisture through rainfall or groundwater," Conservancy scientist Lisa Younger said. “I suppose it’s the upside to a really wet winter.”

Support from donors like you has helped the Conservancy to protect several locations where vernal pools can be found in Washington, including Marcellus Preserve, located north of Ritzville; Turnbull National Wildlife Refuge (where many of these beautiful photos were taken two years ago) and Swan Lakes.

Scientists estimate there are 20 pools on the Marcellus property, but it’s hard to know, since they’re so fleeting. This makes them hard to protect from threats like development.

Another fun fact about vernal pools: They’re salty. Minerals are left behind when they dry up in the summer. And as the shoreline recedes, flowers follow – blossoming in colorful, concentric rings. These flowers include the Downingia, which produces lovely blue blooms.

"There are many interesting flowering annuals," scientist Jim Evans said. "That’s one thing that’s striking about vernal pools – they’re completely different than surrounding shrub-steppe that we usually associate with eastern Washington."


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