GROUNDWATER DEPLETION

Groundwater depletion in the United States: causes, hotspots and how it is measured

What groundwater depletion is, how much the U.S. has lost, where aquifers like the Ogallala are declining fastest, and what falling water tables mean for wells, land and water supply.

By Argos Tellus · Updated October 1, 2026

KEY TAKEAWAYS

Groundwater depletion is a long-term decline in the volume of water stored in an aquifer, caused when pumping exceeds recharge for years at a time.
Roughly 140 million people — almost half the U.S. population — rely on groundwater for drinking water (USGS).
USGS estimated U.S. groundwater depletion of about 1,000 cubic kilometers from 1900 to 2008, with the rate in 2000–2008 (about 25 km³ a year) nearly three times the century-long average.
In the High Plains (Ogallala) aquifer, storage fell by about 286 million acre-feet from predevelopment to 2019, and some wells have recorded water-level declines of more than 250 feet (USGS).
Depletion has consequences beyond lower water levels: dry or less productive wells, higher pumping costs, land subsidence, reduced streamflow and poorer water quality.

What is groundwater depletion?

Groundwater is water stored in the pores and fractures of rock and sediment below the water table. Aquifers are recharged slowly by rain, snowmelt and seepage from streams. Groundwater depletion is the long-term reduction of that stored water — a sustained decline in water levels that does not recover between dry and wet years.

Short-term drawdown is normal: water levels drop during a pumping season and recover afterward. Depletion is different. It happens when withdrawals exceed recharge year after year, so each recovery is incomplete and the trend line keeps falling.

How much groundwater has the U.S. lost?

A U.S. Geological Survey assessment by Leonard Konikow estimated cumulative groundwater depletion in the United States of about 1,000 cubic kilometers between 1900 and 2008. The pace accelerated: depletion averaged about 9.2 km³ a year across the whole period but about 25 km³ a year in 2000–2008.

Groundwater remains central to U.S. water supply. USGS estimates about 140 million people rely on groundwater for drinking water — through public-supply wells and more than 40 million people on private domestic wells — and groundwater supplies close to half of the water used for irrigation.

Where is groundwater depletion worst?

Depletion is concentrated where intensive irrigation or urban demand sits on aquifers with limited recharge.

High Plains (Ogallala) aquifer — spanning parts of eight states from South Dakota to Texas, it supports a large share of U.S. irrigated agriculture. USGS reports storage declined by about 286 million acre-feet from predevelopment to 2019, with an area-weighted average water-level decline of about 16.5 feet and declines of more than 250 feet in some wells. The steepest declines are in the Southern High Plains of Texas and western Kansas.
California Central Valley — heavy pumping during droughts has caused large storage losses and some of the most dramatic land subsidence in the world; USGS documented more than 28 feet of subsidence near Mendota in the San Joaquin Valley between 1925 and 1977. California now regulates basin pumping under SGMA.
Mississippi Embayment and Gulf Coastal Plain — irrigation pumping from the Mississippi River Valley alluvial aquifer and confined coastal aquifers has produced persistent declines.
Desert Southwest — Arizona and parts of Nevada and New Mexico depend on basins with very low natural recharge.

Consequences of falling water tables

Lower water levels are only the first effect. The others are what turn depletion into a financial and operational problem:

Wells go dry or lose yield — shallow domestic wells fail first; production wells lose pump submergence and capacity.
Higher costs — every foot of additional lift raises pumping energy costs, and deeper wells cost more to drill.
Land subsidence — USGS attributes more than 80% of identified U.S. land subsidence (over 17,000 square miles in 45 states) to groundwater withdrawal; compaction of clay layers is largely permanent and reduces aquifer storage (see Houston subsidence).
Reduced streamflow and springs — many streams are fed by groundwater; depletion can dry springs and reduce baseflow.
Water quality changes — declining levels can draw in saline or poorer-quality water, including seawater along coasts.
Asset and lending risk — farmland, developments and industrial sites whose value depends on water can lose value as availability declines.

How groundwater depletion is measured

The most direct evidence is a long record of water levels in monitoring wells. Hydrographs from networks maintained by USGS and state agencies show seasonal cycles and long-term trends. Regional storage change is estimated by combining water-level change with the aquifer’s specific yield or storativity.

Satellite gravimetry (NASA’s GRACE missions) detects large regional changes in total water storage, and InSAR satellite data maps land subsidence. Numerical groundwater models combine these with pumping and recharge data to project how levels will change under future demand — the step needed to turn history into a forecast for a specific site.

Can groundwater depletion be reversed?

Partly, and slowly. Reducing pumping, shifting to surface or reclaimed water, managed aquifer recharge and conservation can stabilize or raise water levels. But where clays have compacted (subsidence), the lost storage does not come back, and in aquifers with very low recharge such as much of the Southern High Plains, depleted water is effectively non-renewable on human time scales.

For anyone relying on a specific aquifer — a farm, a city, a data center or a lender — the practical question is the trajectory at their site: how fast levels are falling, how much saturated thickness is left, and how long current pumping can continue.

Frequently asked questions

What causes groundwater depletion?

Pumping groundwater faster than the aquifer is recharged, sustained over many years. Irrigation is the largest driver in the U.S.; municipal and industrial demand, drought and reduced recharge add to it.

How much groundwater has the United States lost?

A USGS study estimated about 1,000 cubic kilometers of groundwater depletion in the U.S. from 1900 to 2008, with the rate accelerating to about 25 cubic kilometers a year in 2000–2008.

Is the Ogallala aquifer running out?

In parts, yes. USGS reports the High Plains aquifer lost about 286 million acre-feet of storage from predevelopment to 2019. Declines are uneven: some areas are stable, while parts of the Texas Panhandle and western Kansas have lost most of their saturated thickness.

What is the difference between drawdown and depletion?

Drawdown is the local, often temporary, lowering of water levels around a pumping well (the cone of depression). Depletion is a long-term, aquifer-wide loss of stored water that does not recover between seasons.

Does groundwater depletion cause land subsidence?

Yes. USGS attributes more than 80% of identified land subsidence in the U.S. to groundwater withdrawal, as clay layers compact when water pressure drops. Much of that compaction is permanent.

HOW ARGOS HELPS

Phreatic — groundwater availability

Per-aquifer water-level forecasts out to 20 years, saturated-thickness tracking and the Floyd Factor aquifer-health metric.

CARI — aquifer reasoning agent

Ask about water-level trends, drawdown and availability for any site in plain English.

SOURCES

Figures are taken from the primary sources above and dated as of the update shown. Concentrations are expressed in mg/L. Spot an error? Email support@argostellus.com.

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