Vernal Pools

Early American explorers, Zebulon Pike and Randolph Marcy, characterized the southwest as the "The Great American Desert," akin to the Sahara. Yet the Spanish who had settled the area prior to the Americans knew otherwise. Over the course of 150 years, the Spanish had explored and carefully documented the significant water sources of the southwest. Their settlements grew up around these and to this day, place names reflect the importance of water: "rio" for river, "cienega" for marshy places, "laguna" for permanent lakes, and "bosque" for woods near water. Not only were these water sources important to the Spanish, but also to wildlife. For example, New Mexico is along the Central Flyway, a route used by millions of waterfowl on their annual migrations. In a fine orchestration of nature, our seasonal water sources peak with their migration times.

Many of New Mexico's water resources are ephemeral; it rains or the snow melts, the water collects for a time and then disappears. During a springtime hike in Los Alamos, you might notice the most humble of aquatic resources, vernal pools. Vernal is Latin for spring, the typical time of year when heavy rains pool in terrestrial depressions underlain by clay or rock hardpan, which keeps the water from draining out. The pools last only a few weeks or months. As the rains taper off, the pools dry out and flowers move in until the next period of rain starts the cycle again.

Vernal pools are fascinating miniature wetlands with a nearly closed ecosystem and huge food web. Importantly, and due to their seasonal nature, they lack fish, which allows for the safe development of amphibians and insects. Things happen very quickly once heavy rains begin. The buried cyst-like eggs of the Daphnia, or water flea, begin to hatch. They become food for many species including the dragonflies living out their larval phase in the pool. With the advent of rain, aquatic beetles deposit their silk-encased eggs on plants. Spadefoot toads emerge from underground to breed in the pool where their tadpoles hatch and develop. Garter snakes are good swimmers who lie in wait on the banks for a meal of frogs and salamanders. Red-tail hawks swoop down upon unsuspecting lizards and insects. Despite their importance, vernal pools are easy to ignore; some people see them as glorified puddles. Due to their seasonal nature, they are easily destroyed before they are even discovered. Next time you see one of those funny looking puddles, pause for a moment to look for the life that abounds within them.

Collecting Raindrops

The raindrops that splash down on dry ground and eventually form a vernal pool are interesting in themselves. A naturalist named Wilson Bentley wanted to know what raindrops looked like and devised a method to collect them that you can try at home. Beware, you will get wet!

You will need:

• a metal pie plate and piece of cardboard to cover it
• flour
• zip-lock baggies
• ruler
• dark construction paper
• fine mesh strainer.

First, sift the flour into the pie dish so that it is 1 to 1.5 cm deep. Second, cover your pie pan with the cardboard and go outside in the rain. Go where there are no trees or buildings, just you and the sky. Third, briefly remove the cardboard cover from the pan for 8-10 seconds, then cover it back up. Fourth, take your pan inside. The raindrops will have formed little dough balls. Carefully separate these floured raindrops using the sieve. Fifth, dump the raindrops on the construction paper to dry for two minutes. You can sketch, measure and sort your raindrops by size. If you like, you can date a zip lock bag and store your raindrops in the freezer. Did you know that the size of the raindrop indicates how far it fell? While all the drops are generally the same shape, the ones to have fallen the farthest are the largest. Try doing this experiment during different types of rain showers, but definitely do not try it while there is lightning nearby. Be safe and have fun discovering the wonders of nature.