One of the most significant results of groundwater loss is land subsidence, where the ground physically sinks as water is pumped from underground aquifers. But that’s only one piece of a much larger problem. Losing groundwater triggers a chain of consequences that affects everything from the rivers on the surface to the cost of growing food, the safety of drinking water in coastal cities, and the structural integrity of roads and bridges.
The Ground Literally Sinks
When water fills the tiny spaces between sand, gravel, and clay particles deep underground, it helps support the weight of the land above. Remove that water faster than nature can replace it, and those particles compress together permanently. The land above drops. This process, called land subsidence, is irreversible in most cases because once the soil compacts, the aquifer loses its ability to hold as much water even if levels eventually recover.
The scale of sinking can be dramatic. In Vietnam’s Mekong Delta, 25 years of groundwater pumping caused the land to sink an average of 18 centimeters. Current rates there reach 1.1 centimeters per year on average, with some areas dropping more than 2.5 centimeters annually. That’s roughly ten times faster than global sea level rise, meaning the land is racing downward even as the ocean creeps upward.
In California’s San Joaquin Valley, subsidence has been so severe that at least one bridge now sits below the waterline, requiring a $2.5 million replacement. Rebuilding a single damaged canal cost $4.5 million, and long-term infrastructure repair costs across the region are estimated in the billions. Roads crack, pipelines break, and water delivery systems that were engineered for a surface that no longer exists need constant, expensive fixes. The California Department of Water Resources has already spent tens of millions of dollars repairing its main aqueduct and expects to spend at least that much again.
Rivers and Streams Lose Their Water Source
Most people think of groundwater and surface water as separate systems, but they’re deeply connected. Many rivers and streams are fed from below by groundwater seeping up through their beds. When pumping pulls the water table down, that upward flow slows or stops entirely. At higher pumping rates, the relationship can actually reverse: instead of groundwater feeding the stream, the stream starts losing water downward into the depleted aquifer.
This shift has real consequences for ecosystems. Modeling of California’s Santa Rosa Plain shows that increased pumping under future climate scenarios leads to declining groundwater levels, reduced groundwater discharge into streams, and a growing number of stream reaches that lose water instead of gaining it. Fish populations suffer directly. Along the San Joaquin River, a major federal program is working to restore natural river ecology specifically to bring back salmon and other fish that depend on consistent streamflow.
Wetland plants are among the first casualties. Research in Colorado’s San Luis Valley tracked what happened after a sustained drop in the water table: wetland grasses and grass-like species declined significantly, replaced by drought-tolerant shrubs like greasewood and rabbitbrush. The landscape shifted from a wetland community to something much drier, changing the habitat for every species that depended on it.
Saltwater Contaminates Coastal Drinking Water
Along coastlines, freshwater in underground aquifers naturally pushes against saltwater from the ocean. The two meet at an equilibrium point, and as long as there’s enough freshwater pressure flowing seaward, the salt stays out. Pump too much freshwater from coastal wells, and that pressure drops. Saltwater then migrates inland into the aquifer, contaminating wells that communities depend on for drinking water.
Florida provides a clear example of how this plays out. As freshwater levels in the state’s aquifers have dropped relative to sea level, saltwater has moved in through multiple pathways. Once an aquifer is contaminated with salt, it’s extremely difficult and expensive to reverse. Wells may need to be abandoned, and communities face the cost of finding alternative water sources or building desalination infrastructure.
Agriculture Faces Rising Costs and Falling Yields
About 70% of groundwater withdrawn worldwide goes to agriculture, and in the United States, roughly 71% of groundwater pumping supports crop irrigation. That makes farming the single largest driver of aquifer depletion, and also the sector most vulnerable to its consequences.
As water tables drop, the most immediate hit is economic. Pumping water from greater depths requires more energy, which raises costs for every acre irrigated. For farmers operating on thin margins, those rising costs can make certain crops unprofitable. Over time, if an aquifer is drawn down far enough, some wells simply stop producing. Research focused on California’s Central Valley projects that over 9,000 domestic wells and around 1,000 public supply wells could be affected if groundwater continues declining at current rates through 2040.
The long-term concern is food production itself. Regions that became agricultural powerhouses because of abundant groundwater, like the Central Valley or the area above the Ogallala Aquifer in the Great Plains, face a future where that water is no longer reliably available. Without groundwater, these areas would need to either shift to rain-fed farming with significantly lower yields or find alternative water sources that may not exist at the needed scale.
The Problem Is Accelerating
Global groundwater depletion, the gap between how much water is pumped out and how much naturally recharges, is projected to reach 887 cubic kilometers by 2050. That’s about 61% more than 2021 levels. The trend line points sharply upward, driven by population growth, expanding irrigation, and climate patterns that reduce natural recharge in many regions.
What makes groundwater loss particularly challenging is that its effects compound. Subsidence makes flooding worse in sinking coastal areas. Saltwater intrusion removes aquifer capacity that was already shrinking. Dried-up streams can’t recharge the aquifers they once connected to. Each consequence reinforces the others, making recovery harder the longer depletion continues. And because aquifer compaction is permanent, some of the storage capacity lost today is gone for good.