Vernal (spring) pools are intermittent bodies of water found almost uniquely in California. Due to impervious bottoms (rock, hardpan or claypan), rainfall collects in these shallow depressions and cannot percolate through. The remaining water slowly evaporates from the pool. This temporary wetness signals the awakening of a great deal of life. Seeds and spores germinate, eggs hatch and cysts resume their embryonic development.
Within weeks, a myriad of invertebrates are swimming throughout the pool, grazing on algae and bacteria. Seeds of showy wildflowers germinate and the once-dry shallow depression is transformed into a wildflower garden teeming with life. Before the season is over, a grand succession of wildflowers has bloomed and gone to seed, scores of invertebrates have lived their short but full lives, frogs and toads have mated and their tadpoles have metamorphosed.
This ephemeral but rich ecosystem is truly amazing. Sierra College's vernal pools include those incidentally made from nineteenth century gold excavation sites in the northeastern portion of the campus, and a man-made demonstration pool near the cactus and rock garden of Sewell Hall.