What is the most depleted aquifer in the US?

The High Plains (Ogallala) Aquifer is the most depleted, having lost approximately 330 cubic kilometers of water since 1950. Parts of Kansas and Texas have lost 30-50% of their saturated thickness.

What causes land subsidence from groundwater pumping?

When groundwater is pumped from compressible clay layers, the sediments compact permanently, causing the land surface to sink. California's Central Valley has sunk up to 28 feet in some areas.

✓ Last Updated: February 2026

Aquifer Depletion Statistics 2026: 45 Facts & Data

Q: How much groundwater has been depleted?

Since 1950, approximately 1,000 cubic kilometers (270 trillion gallons) of groundwater has been depleted from U.S. aquifers, with depletion rates accelerating in recent decades.

Q: How fast are aquifers declining?

Depletion rates vary by region. The Ogallala declines 1-3 feet per year in heavily pumped areas. California's Central Valley has seen declines of 5-10 feet per year during droughts.

Q: What is groundwater overdraft?

Groundwater overdraft occurs when pumping exceeds natural recharge. California has 21 critically overdrafted basins under SGMA, and the Ogallala Aquifer is overdrawn by millions of acre-feet annually.

Comprehensive data on groundwater depletion, aquifer overdraft, land subsidence, and sustainability challenges from USGS and scientific sources.

1,000

km³ Depleted (US)

CA Basins Overdrafted

28 ft

Max Subsidence (CA)

30%

Ogallala Depleted

U.S. Aquifer Depletion Overview

1,000 km³ (270 Trillion Gallons) Total groundwater depleted from U.S. aquifers since 1950

Source: USGS Groundwater Depletion in the United States

National Depletion Statistics

Metric	Value
Total depletion since 1950	~1,000 km³
Annual depletion rate (2010-2020)	~25 km³/year
Depletion rate acceleration	3x since 1950
States with significant depletion	40+
Major aquifers in decline	30+

Key Facts

Depletion has tripled since 1950 due to irrigation expansion
Most depletion irreversible on human timescales (centuries to recover)
Half of depletion concentrated in High Plains and California
Climate change expected to accelerate depletion
$2 billion/year economic losses from depletion-related issues

Major Aquifer Depletion

Most Depleted U.S. Aquifers

Aquifer	Depletion	Decline Rate	Status
High Plains (Ogallala)	~330 km³	1-3 ft/year	Critical
Central Valley, CA	~150 km³	2-10 ft/year	Critical
Mississippi Embayment	~70 km³	0.5-2 ft/year	Declining
Atlantic Coastal Plain	~50 km³	0.5-1 ft/year	Moderate
Arizona Basin & Range	~45 km³	1-4 ft/year	Active mgmt

Ogallala Aquifer Statistics

Extent: 174,000 square miles across 8 states
Depletion: 30% of original volume lost
Kansas: Some areas 60% depleted
Texas Panhandle: 50% saturated thickness lost
Recharge rate: 0.5-1 inch/year (vs. 15-20 inches pumped)
Time to recovery: Estimated 6,000+ years natural recharge

California Depletion

21 Critically Overdrafted Basins California basins designated critically overdrafted under SGMA

Source: California DWR SGMA

Central Valley Statistics

Metric	Value
Total depletion since 1960	~150 km³
Annual overdraft	2-3 million acre-feet
Drought-year overdraft	5+ million acre-feet
San Joaquin Valley decline	Up to 100+ feet since 1960
Critically overdrafted basins	21

SGMA Critically Overdrafted Basins

Kern County Subbasin
Tulare Lake Subbasin
Tule Subbasin
Kaweah Subbasin
Kings Subbasin
Westside Subbasin
Delta-Mendota Subbasin
Chowchilla Subbasin
Madera Subbasin
Borrego Valley
... and 11 others

Land Subsidence

28 Feet Maximum recorded land subsidence in California's Central Valley

Source: USGS California Land Subsidence Program

Subsidence Statistics

Location	Total Subsidence	Rate
San Joaquin Valley (max)	28 feet	Historical
San Joaquin Valley (recent)	0.5-2 ft/year	Active
Houston, TX	10+ feet	Managed
Phoenix, AZ	18+ feet	Historical
Las Vegas, NV	6+ feet	Managed

Subsidence Impacts

Infrastructure damage: Roads, bridges, canals, pipelines
Reduced aquifer capacity: Permanent storage loss
Flooding risk: Lowered land elevations
Well damage: Casing collapse, reduced capacity
California canal damage: Billions in repairs needed

Depletion Impacts

Well Owner Impacts

Deeper wells required: 50-200+ feet deeper over time
Increased pumping costs: 2-3x higher energy bills
Dry wells: Thousands of domestic wells have gone dry
Well deepening costs: $15,000-50,000 typical
New well costs: 25-40% higher than a decade ago

Environmental Impacts

Stream depletion: Reduced baseflow to rivers
Ecosystem loss: Wetlands and springs drying
Seawater intrusion: Coastal aquifer contamination
Water quality decline: Concentration of contaminants

Frequently Asked Questions

How much groundwater has been depleted?

Since 1950, approximately 1,000 cubic kilometers (270 trillion gallons) has been depleted from U.S. aquifers.

What is the most depleted aquifer?

The High Plains (Ogallala) Aquifer has lost approximately 330 km³ since 1950, with some areas 50-60% depleted.

How fast are aquifers declining?

Rates vary from 1-3 feet/year in the Ogallala to 5-10 feet/year in California during droughts.

What is groundwater overdraft?

Overdraft occurs when pumping exceeds natural recharge. California has 21 critically overdrafted basins.

Can depleted aquifers recover?

Some can recover over decades with reduced pumping, but compacted aquifers suffer permanent storage loss.

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