More likely, they were for the native grasses and herbs that grew on this 10,000 acre coastal prairie. A favorite of cattle on long hot days is the saltgrass which gets munched flat to the ground. Maybe these were the grains of the ancient Kumayaay tribes. The answer is clay. Crumbly beds of gray and chocolate brown clay that float like huge paddies of seaweed on the undulating plain are what support grasslands over shrub lands.
Clays are also the reason that there are little trapped lakes left after winter rains.
These are the vernal pools and they are the proof that this habitat has been around for a very long time. There are many plants, a few toads and crustaceans, and lot of unknown things that have evolved on in the vernal pools of Southern California. These pools are rich reservoirs of life. All of these unique plants can survive harsh soils, summer drought and 'breathe underwater' in the winter. The vernal pools of Ramona Valley have their own uniqueness, though there has been barely enough time to notice it as the town of Ramona swallows up most of the main pools.