“Eventually man will be competing with crops for water!”
With an alarmingly dry winter and California reservoirs dropping fast, groundwater increasingly is keeping the state hydrated. It now accounts for about 60 percent of California’s water supply. But unlike its rivers, lakes and reservoirs, the state does not consider groundwater part of the public good. It does not regulate groundwater like it does surface water. Landowners can pump as much water as they want.
Humans have utilized aquifers for water for thousands of years, with evidence of wells dating back to the Stone Age, nearly 10,000 years ago. While, according to Rutgers University, early humans in East Africa may have relied on spring-fed groundwater 1 to 2 million years ago during dry periods, engineered water wells and gallery systems have been used for thousands of years, with many dating from 1,000 B.C..
Key Historical Uses of Aquifers:
Stone Age (approx. 10,000 years ago): Archaeological evidence points to the earliest water wells in places like Cyprus.
Ancient Civilizations: Civilizations in the Mediterranean, Egypt, and the Middle East constructed complex, horizontal, and vertical infiltration galleries.
“Fossil” Water Usage: Humans have long tapped into “fossil” water, which is groundwater that has been in the aquifer for thousands of years. The Nubian Sandstone Aquifer System has been a critical water source for millennia.
Modern Era: While groundwater usage was largely local for thousands of years, the 20th century saw massive increases in pumping for irrigation and industrial needs, notably from sources like the Ogallala Aquifer.
Today, the reliance on these ancient, often non-renewable, water sources continues, with some extracted water dating back 15,000 to 20,000
“Any manipulation of the water tables that are not in the public good should be carefully examined.”
Groundwater levels in California have experienced significant, long-term declines over the last 50 years, particularly in the Central Valley, driven by intense agricultural overdraft and, more recently, accelerated by severe drought. While wet years (e.g., 2017, 2019, 2023) provide temporary, partial recovery, particularly in shallow aquifers, many deeper, long-term supplies have dropped over 100 feet below historical lows.
Persistent Decline: Since the 1980s, dozens of basins have been identified as in “critical” overdraft, with 40+ basins in significant decline.
Acceleration: According to NASA GRACE data, the rate of depletion in the Central Valley accelerated from 2003 onwards, with massive losses during the 2012-2016 drought.
Deep vs. Shallow Aquifers: While wet years and flood-managed recharge have helped replenish shallower, localized water tables, deep, ancient aquifers (sometimes 20,000 years old) have failed to recover fully from sustained, decades-long pumping.
Subsidence: The dramatic, long-term drop in water levels has caused significant land subsidence (sinking) in the San Joaquin Valley.
Current Status: As of 2023-2025, while 2023 provided massive, temporary, localized relief, many deeper aquifers remain in long-term deficit, requiring multiple, consecutive, or sustained wet periods to fully recover.
Regional Variations:
Central Valley: Experienced the most dramatic declines, with some areas seeing water tables drop more than 100 feet below previous historic lows.
Southern California (Mojave): Experienced significant declines since the 1950s, but some areas have seen 14-260 ft recovery since the 1990s due to managed, imported water recharge.
San Francisco Bay: Generally observed the most stable, though often, declining levels.
Long-term management is shifting under the Sustainable Groundwater Management Act (SGMA), with 2023 showing significant (4.1 million acre-feet) managed recharge, yet long-term deficits persist.
