OGALLALA AQUIFER

The Ogallala aquifer: how fast it is declining, where, and what it means

Ogallala (High Plains) aquifer depletion explained — how much water has been lost, which areas are declining fastest, why recharge cannot keep up, and what it means for farms, towns and new water users.

By Argos Tellus · Updated October 1, 2026

KEY TAKEAWAYS

The High Plains aquifer — of which the Ogallala Formation is the main unit — underlies about 174,000 square miles in eight states: Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas and Wyoming (USGS).
About 27% of U.S. irrigated land overlies it, and it supplies about 30% of the groundwater used for irrigation in the United States (USGS).
From predevelopment (about 1950) to 2019, water in storage fell by about 286 million acre-feet — an area-weighted average water-level decline of about 16.5 feet (USGS).
Decline is highly uneven. Much of Nebraska is close to stable, while the Texas Panhandle, the Southern High Plains and western Kansas have lost a large share of their saturated thickness — some wells more than 250 feet of water level.
In the southern aquifer, natural recharge is a small fraction of pumping, so depletion there is effectively permanent on human time scales.

What is the Ogallala aquifer?

The Ogallala Formation is a layer of sand, gravel, silt and clay eroded from the Rocky Mountains and deposited across the Great Plains millions of years ago. Together with connected younger deposits it forms the High Plains aquifer, one of the largest aquifers in the world and the principal water source for one of the most productive agricultural regions in the United States.

More than 95% of the water withdrawn from the High Plains aquifer is used for irrigation, according to USGS. It also supplies drinking water to cities and towns across the region, from Lubbock and Amarillo to communities in Kansas, Oklahoma and Nebraska.

How much has the Ogallala declined?

USGS has tracked High Plains water levels since large-scale irrigation began in the 1940s and 1950s. Its most recent comprehensive assessment estimated that recoverable water in storage fell by about 286 million acre-feet between predevelopment and 2019, leaving about 2.9 billion acre-feet. The area-weighted average water-level decline across the aquifer was about 16.5 feet.

The averages hide the problem. Because the aquifer is thick and stable in the north and thin and heavily pumped in the south, a 16.5-foot average includes areas with little change and areas where most of the usable water is already gone.

Measure (predevelopment to 2019)	Value	Source
Area of aquifer	≈174,000 sq mi in 8 states	USGS
Decline in water in storage	≈286 million acre-ft	USGS SIR 2023-5143
Water remaining in storage (2019)	≈2.9 billion acre-ft	USGS SIR 2023-5143
Area-weighted average water-level change	≈16.5 ft decline	USGS SIR 2023-5143
Largest declines at individual wells	More than 250 ft	USGS SIR 2023-5143

Where is the Ogallala declining fastest?

Texas Panhandle and Southern High Plains — the thinnest saturated thickness and some of the largest declines; many areas can no longer support full irrigation and have shifted to dryland farming.
Western Kansas — large declines in the southwest of the state, where Kansas has created local enhanced management areas to reduce pumping.
Oklahoma Panhandle and eastern New Mexico — significant declines tied to irrigation.
Nebraska — holds most of the aquifer’s water; parts of the state have seen little net decline, and some areas have risen where surface-water irrigation recharges the aquifer.

Why recharge can’t keep up

Recharge in the High Plains comes mostly from rain and snowmelt that infiltrates through thick unsaturated sediments. In the semi-arid southern plains, high evaporation and low rainfall mean recharge is measured in fractions of an inch to an inch or so a year in many places — while irrigation pumping removes far more. Where the water level falls a foot or more a year, it would take centuries of recharge to replace what has been pumped.

This is the textbook case of groundwater depletion: water that accumulated over thousands of years is being mined faster than it is replaced.

What Ogallala decline means for farms, towns and new water users

As saturated thickness shrinks, well yields fall, pumps must be lowered, more wells are needed to irrigate the same field, and eventually irrigation becomes uneconomic. Irrigated land converts to dryland production, which earns less and is worth less — a direct risk to farmland values and agricultural lending.

Towns that depend on the aquifer face rising costs to drill deeper wells or import water. And new large users — ethanol plants, feedlots, data centers — siting on the High Plains add demand to an aquifer already in decline. In Texas, local groundwater conservation districts set the production rules that determine how much of the remaining water any one user can take.

How to assess Ogallala water at a specific property

Regional maps show the trend; decisions need the parcel. A site-level assessment uses nearby well records to establish current saturated thickness and its rate of decline, projects how many years of pumping at a given rate the aquifer can support, and checks well interference and district rules. The result can be expressed as years of irrigation (or supply) remaining — the number that matters for land value, lending and siting.

Frequently asked questions

Is the Ogallala aquifer running dry?

In parts of it, effectively yes. USGS estimates about 286 million acre-feet of storage was lost from predevelopment to 2019. Declines are concentrated in the Texas Panhandle, Southern High Plains and western Kansas, where some areas can no longer sustain irrigation; much of Nebraska remains comparatively stable.

How big is the Ogallala aquifer?

The High Plains aquifer, of which the Ogallala is the main formation, underlies about 174,000 square miles in Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas and Wyoming, and held about 2.9 billion acre-feet of recoverable water in 2019 (USGS).

How much U.S. irrigation depends on the Ogallala?

About 27% of irrigated land in the United States overlies the High Plains aquifer, and it supplies about 30% of the groundwater used for U.S. irrigation, according to USGS.

Can the Ogallala aquifer recharge?

Slowly. Recharge from precipitation is low across the semi-arid southern plains, far less than current pumping, so depletion there is effectively permanent on human time scales. Recharge is higher in parts of Nebraska and where surface-water irrigation seeps into the aquifer.

HOW ARGOS HELPS

Phreatic — groundwater availability

A dedicated Ogallala model among its per-aquifer forecasters, with saturated-thickness tracking and sustainable yield.

CARI — aquifer reasoning agent

Ask how long a property’s wells can sustain irrigation, 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.

RELATED GUIDES

Need a site-specific answer?

Argos models groundwater availability, drawdown and contamination for individual sites and portfolios.

CONTACT ARGOS