Vernal or ephemeral pools, are temporary pools of water. They are usually devoid of fish, and thus allow the safe development of natal amphibian and insect species. Most pools are dry for at least part of the year and fill with the winter rains. Pools may remain at least partially filled with water over the course of a year or more, but all vernal pools dry up periodically.
They are called vernal pools because they are often, but not necessarily, at their peak depth in the spring ("vernal" meaning of, relating to, or occurring in the spring). Despite being dry at times, once filled they teem with life making them an important asset to the ecology of an area. The Banning Ranch area hosts many vernal pools.