Groundwater
In
an average year, approximately 30% of California's water needs are
met by groundwater. In times of drought, groundwater consumption can
rise to as much as 60%! The dependence on groundwater during dry years
is based on the existence of hundreds of millions of acre-feet of
water in California's 450 groundwater basins compared to approximately
45 million acre-feet in California's 1,200 surface water reservoirs
(ACWA
Groundwater Committee).
So just what is this abundant resource known as groundwater? Groundwater
is found under the earth's surface. Most groundwater is a result of
rain and melted snow that has soaked into the ground, making it a
self-replenishing source. Some groundwater has existed for millions
of years. While there are no actual underground rivers, groundwater
seeps into the ground by making its way into cracks and spaces in
sand, soil, and rocks, forming an aquifer. From the aquifer, the water
is brought back to the surface naturally through springs, sometimes
discharging into lakes and streams, or via man-made wells.
Aquifers
are replenished through a process known as recharge. Recharge can
be a naturally occurring process as part of the hydrologic cycle as
rainfall infiltrates the land surface and percolates into the underlying
aquifers. Natural recharge occurs at different rates in different
areas due to variations in properties such as soil types, plant cover,
land slope, and rainfall intensity. In addition to rainfall recharge,
bodies of surface water may also recharge groundwater aquifers by
seeping from the sides of water bodies and percolating into the aquifer.
A third source is artificial recharge where aquifers are directly
replenished through the pumping or injecting of water into the wells
or by spreading water over a land surface, allowing it to seep into
the aquifer at a natural rate. Artificial recharge is also a useful
tool to dilute contaminated groundwater supplies.
Contamination is one of the major hazards of groundwater. Groundwater
is vulnerable to pollution from both natural contaminants and human
negligence. The Environmental
Protection Agency provides information on activities leading to
ground water contamination. Since groundwater is below the surface
of the land, it is extremely difficult and expensive, and many times
impossible, to remove the contaminants from a contaminated groundwater
source. Unfortunately, many groundwater reservoirs remain contaminated
for hundreds of years, if not forever, once contamination is detected.
Some
of the many resources concerning groundwater include:
Department
of Water Resources Groundwater Information Center
Department
of Water Resources, Water Facts: 7-Steps for Managing Groundwater
Supplies
Department
of Water Resources, Water Facts: Ground Water
Department
of Water Resources, Water Facts: Groundwater Management in California
- Six Methods Under Current Law
Department
of Water Resources, Groundwater Management in California: AB 3030
Water
Systems Council, Wellcare: Where Your Water Comes From
National Ground Water
Association
Well
Owner.org
