Groundwater is vitally important to California and is used to provide drinking water to customers, irrigation for farmers and support natural environments. Water districts and cities often use groundwater as their primary water source rather than purchase expensive imported water. “Imported” water is any water that is not produced and treated for distribution locally. Typically, imported water comes from several rivers in Northern and Central California or from the Colorado River. In Southern California, which is prone to multi-year droughts, groundwater can make up as much as half of a water supply portfolio depending on the water provider.
Aquifers, which can be thought of as underground lakes, are unique and have different characteristics. Some aquifers are relatively small while others like the Ogallala (Ogah-La-La) Aquifer cover several states! Sometimes there can be several aquifers stacked on top of each other in the same area. When this happens, the aquifers are often referred to as “perched” aquifers. California has several hundred aquifers throughout the state.
Aquifers can form in different environments, but they are often found in basins. Over millions of years, rivers erode rock and sediment layers and naturally fill the basin in. The water eventually stops moving down as it hits a hard rock layer and starts to fill up the basin. As the cycle repeats itself, eventually the basin forms distinct layers and fills with groundwater.
So why does California have so much groundwater? California’s unique and active geology is the primary reason why we have more groundwater than surrounding states. Earthquakes, erosion, flooding, glaciers and even volcanoes have each played their part in helping form aquifers and basins. For millions of years, these natural forces have caused the layers of rock, sediment, and other materials to shift and form basins and aquifers.