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Vernal Pools

Geology & Hydrology

Millions of years of geology and evolution have created the spectacular vernal pools at Sacramento County’s Mather Field. These are exceptional examples of a rare wetland ecosystem that is unique to California. Visitors can experience this piece of California’s natural history, just 20 minutes from downtown Sacramento.

While the vernal pools at Mather Field range from 50,000 to 200,000 years old, the soils under them began forming more than two million years ago. Dissolved minerals slowly moved down through the soil, eventually forming a hardpan layer. This hardpan lies a few inches to a few feet below the soil surface.

In a vernal pool grassland, the movement of rainwater through the soil is stopped by a cement-like layer called hardpan. The water stays perched above the hardpan, where we see it in the shallow depressions called vernal pools. The pools host hundreds of species of tiny aquatic organisms.

The 3 Phases: Wet, Flowering, Dry

Vernal pools have three distinct phases: the wet phase, the flowering phase, and the dry phase.

1. The Wet Phase

Vernal pools have three distinct phases: the wet phase, the flowering phase, and the dry phase. In winter, vernal pools swarm with aquatic life, most smaller than a freckle. Frogs and toads come to mate and lay eggs. From November through March, species race against the clock (and their predators) to grow up, mate and lay eggs before the pools dry up.

Many vernal pool seeds sprout in November with the first winter rains. The seedlings remain less than two inches tall throughout the winter as the pools fill with water, submerging them for weeks or months.



Wet phase

2. The Flowering Phase

As the pools dry down in March, the seedlings grow, springing into bloom during April and early May. Most grow to less than six inches high. Vernal pool flowers create colorful rings, patches and ribbons of yellow, white, pink and purple.

The displays change from week to week, as each species gives way to the next, like a floral kaleidoscope.



The flowering phase

3. The Dry Phase

During the hot, dry summer months, vernal pools lie brown and barren among the grasslands. Birds, mammals and insects come to the pools to feed on the seeds and bulbs of vernal pool plants. While they are there, other species feed on them.

The sun-baked bottoms of the vernal pools hold the eggs, cysts and seeds that will give life to the next generation. The winter rain awakens them, restarting the cycle each year.



Student outside Splash Center

Visiting Vernal Pools

Visiting the Illa Collin Conservation Preserve at Mather Field

Public access in Mather’s vernal pool habitat is limited and prohibited in some of the surrounding areas. We only have about 5% of the vernal pools we once had in California. We hope you will take time to enjoy and protect those that remain. For the benefit of future visitors and hundreds of vernal pool species, please:

Explore the area only on foot – no bicycles or motorized vehicles.

  • Avoid walking into or along the edges of vernal pools. Avoid stepping on flowers.
  • Keep dogs on leashes and out of restricted areas. Look for “No Dogs Allowed” signs.
  • Leave all flowers for their pollinators and other visitors.
  • Unless you are on a guided tour, visit only areas open to the general public.
Click to expand the map.

Click on a walking tour location below to find directions, walking instructions and a list of animals or plants you might see.

Walking Tour #1: Fields of Gold

Directions: Take highway 50 to Zinfandel Drive.  Head south on Zinfandel until it turns into a dirt road (past the Douglas intersection, Mather golf course and Woodring drive).  On your left you will see the old munitions complex of the Mather Air Force Base.  Please do not trespass beyond the yellow gate into the munitions complex and please do not block the gate when you park.  You may park safely on the pavement or along the dirt road and head into the field to the southeast from the intersection (to the left and continuing away from Douglas).  During the spring, there is usually a sea of bright yellow Frying Pan Poppies on the east side of the road.

GPS Coordinates: (38.5398745, -121.2600192); GPQQ+WX Mather, California

On your walk, you may discover:

Walking Tour 1

Walking Tour #2: Vernal Pool Complex

Directions: This location is across the dirt road from Walking Tour #1 (on the west side of Zinfandel). Take highway 50 to Zinfandel Drive. Head south on Zinfandel until it turns into a dirt road (past the Douglas intersection, Mather golf course and Woodring drive). Walk or drive about 300 yards down the dirt road until you reach a green kiosk on the western side (be cautious, the road is rather bumpy). Park safely along the dirt road. Follow the foot trail from the kiosk west out into the field. As you walk along the path, on your left you will see a few vernal pools.

If you continue on, eventually you will reach a giant vernal pool known as the Huell Howser pool, named after the late and great host of the show “California’s Gold.” Head further south down the dirt road to find even more vernal pools (on the western side): find “#2 Continued” on the map.

GPS Coordinates for start of Walking Tour #2: (38.5376390, -121.2614830); GPQQ+3C Mather, California

GPS Coordinates for #2 Continued: (38.5345330, -121.2615110); GPMQ+R9 Rancho Cordova, California

On your walk, you may discover:

Walking Tour #3: Marilyn Evans Pond

Directions: Take highway 50 to Zinfandel Drive.  Head south on Zinfandel, past the Douglas intersection and Mather Lake.  Towards the end of Mather Golf Course, instead of continuing on to the dirt road, turn right onto Woodring Drive.  Head down Woodring until you reach a stone gazebo and a sign that reads “Independence at Mather,” where the residential area begins (see photo to the right).  Park your vehicle safely along the road and follow the trail that begins at the stone gazebo, going north.  If you keep following this trail, past the old paved helicopter landing pad, you will eventually reach Marilyn Evans Pond.  Here you can find an array of birds as well as evidence of Beaver activity such as felled trees, chomped trunks and branches, and even a big den.

GPS Coordinates: (38.5469030, -121.2692860); GPWJ+Q7 Mather, California

On your walk, you may discover:

  • Plants are mostly grasses (upland) – soaproot, hawkbit, filaree, medusahead (invasive), white hyacinth, willows, cottonwoods
  • Trees and branches worn away by Beaver teeth
  • Felled trees caused by Beavers
  • Big Beaver den
  • Beaver dam
  • A resident Beaver
  • Mallards
  • American Coots
  • Black-Crowned Night Herons
  • Great Blue Herons
  • Great Egrets
  • Mute Swans (invasive)
  • Tree Swallows

Virtual Tour of the Mather Field Vernal Pools

Take an 8-minute tour of the Mather Field vernal pools! The area featured in this video is prohibited to the public, so this is your chance to explore it virtually. It was filmed in late March during the pools’ transition into the flowering phase. Enjoy!



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