Mather Field Vernal Pools

Introduction to Vernal Pools


Photo of dry mud with animal tracks 
and dove weed in a vernal pool.

 What are Vernal Pools?

California vernal pools are a rare type of wetland that exists in very few places on Earth. Around Sacramento, the pools are found in rolling grassland. What makes vernal pools different from other wetlands, ponds or lakes is that they are temporary pools. They are totally dry for eight months of the year during our dry season. In fact in order to have vernal pools, you need a wet season and a dry season, just like the Mediterranean climate of California.

In Sacramento most rain falls in the winter between December and March. This is when the vernal pools fill with water. Once the rain stops in the spring, the pools begin to evaporate. By the end of April, the pools fill with tiny flowers growing from the once muddy bottom. Vernal pools are so colorful in spring, they are named for spring: Vernal means "spring" in Latin.

Within a few weeks all of the flowers have made their seeds and the plants have dried up. By July all that remains of the vernal pools is dried, cracked soil and a carpet of short, brown plants. The pools rest like this for another six months until the winter rains return. Then the cycle begins again.


Winter
Wet Phase
Spring
Flower Phase
Summer/Fall
Dry Phase

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