What is Groundwater?

Right under your feet, millions of gallons of water exist between rocks, sand, and gravel. Those permeable bodies of rock and sediment that are saturated with water are called aquifers.  Much of the water in the world exists below the surface- in fact, there is twenty to thirty times more water in the ground than there is in all the earth’s rivers and lakes. During dry years like this one, groundwater fills up bodies of surface water and serves as a “critical buffer against the impacts of drought and climate change.” In some communities, it is the only source of drinking water. Groundwater also provides water for agricultural operations. But that’s not all.

Did you know?

💧 97% of all liquid freshwater on earth is groundwater. (Meaning- most freshwater that is not frozen in glaciers and is available to humans is groundwater.)

💧 Groundwater provides almost 40% of California’s total water supply, with that percentage increasing to 46% or more in dry years.

💧 CA’s Department of Water Resources estimates that the state’s 515 groundwater basins have a storage capacity of between 850 million and 1.3 billion acre-feet. This is an incredible amount when compared to the less than 50 million acre-feet that can be stored in all of CA’s major reservoirs.

Groundwater is essential to every facet of life in our state and region and has immense potential to increase our resilient water supply.


Sustaining Groundwater Supplies with Better Management

In the Central Valley this essential resource was being pumped from the ground faster than it could be replenished. Results of this include lower groundwater levels, which in some areas can cause the ground elevation to lower. This is called subsidence, which can cause damage to surface structures such as roads, building foundations, aqueducts, bridges, pipelines, and flood control structures.

When groundwater is not managed sustainably, water quality can also be impacted. Water quality can degrade due to over pumping, limiting its use for irrigation or drinking without expensive treatment.

Sustainable management of groundwater is needed to address these issues, in addition to avoiding the costs of energy expenses required to pump groundwater from greater depths, the expense of fixing damages caused by land subsidence, and subsequent indirect impacts such as higher food prices.

With these costs in consideration, it is evident that groundwater must be managed sustainability for the well-being of our Central Valley communities, agricultural operations, and economy.


Solutions at the Local Level

GSA map of the Kings and Tulare Lake Subbasins. Click image to find your GSA.


In 2014, California Governor, Jerry Brown passed the Sustainable Groundwater Management Act. This piece of legislation is commonly known as SGMA. SGMA requires local governments and water agencies to bring groundwater basins into balanced levels of pumping and recharge by 2040.

This led to the creation of Groundwater Sustainability Agencies (GSAs), which are agencies that manage groundwater at the local level.

GSAs designed Groundwater Sustainability Plans, (GSPs), documents that outline the agencies’ detailed plans for achieving sustainability. GSAs work with local landowners and communities on implementing their GSPs. (We love our acronyms in the water industry!)


Measuring Groundwater Sustainability

Under SGMA, sustainability is measured using “sustainability indicators” which include: groundwater storage, groundwater levels, interconnected surface water, water quality, and land subsidence. The sixth indicator, seawater intrusion, is not applicable to the Central Valley GSAs. Learn more about each sustainability indicator through the following graphics:



Securing Groundwater for Future Generations

Meeting each of these measurable objectives and achieving sustainability in the Central Valley is not a job for one group, agency, or industry. Groundwater sustainability requires the collaborative efforts of landowners, farmers, residents, policy makers, advocacy groups, engineers, water providers, and more!

You are part of the solution. Connect with your local GSA, advocate for policies that promote groundwater sustainability, innovate recharge projects, and stay in touch with organizations like KRCD to receive regular updates on Central Valley groundwater.

As Leonardo Da Vinci said, “water is the driving force of all nature.” Together, we can ensure this powerful resource is available for generations to come.


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