Geological Resources - Groundwater

Many people don't realize that there is far more fresh water underground than there is flowing on the earth's surface. For example, groundwater makes up an estimated 75% of the water used for agricultural, industrial and domestic use in Santa Barbara County. Groundwater is water that is trapped in the cracks and tiny pore spaces within rocks and sediments. Precipitation and surface runoff percolate through topsoil and down into open spaces within the earth's crust, until the water reaches an impermeable layer. Water continuously accumulates within the earth to form underground reservoirs, called aquifers. Groundwater interacts with geology, topography and surface runoff to form rivers and lakes. Understanding the rock structure and composition is important both for understanding how that groundwater affects vegetation growth, stream recharge and aquatic wildlife species, and in determining its availability for human use.

The volume of water in an aquifer is dependent upon its lateral extent, but also upon the volume of cracks and pore space in the aquifer's host rock. Different rock types have different volumes of pore spaces, which makes some rocks better aquifer hosts than others. Thus the bedrock geology in a given region affects how much groundwater there is and how deep it is to the water table. For example, some sandstone bedrock is very porous and capable of containing large volumes of water, while a dense, unfractured shale may act as an impermeable rock unit and restrict underground flow.

Both groundwater and dammed reservoirs in Los Padres National Forest provide drinking water for many of the surrounding communities. Forest Service campgrounds are generally supported by wells, which tap groundwater resources. The Forest Service regularly monitors its groundwater wells and surface water sources for quality. In Los Padres we are actively working to maintain and restore watersheds, so that they can continue to be both a habitat for fish and wildlife, and a resource providing clean, usable water.