The Ogallala Has Lost 286 Million Acre-Feet Since 1950. Kansas Land Prices Already Show It.

The High Plains aquifer — better known as the Ogallala — underlies 111.8 million acres across eight states, from South Dakota to Texas.▸ Farmers began drawing on it in the late 1890s; large-scale irrigation pumping, and the water-level declines that came with it, took off around 1950. Three-quarters of a century later, the U.S. Geological Survey has the running total, and Kansas land markets already have a price on what's left.

The USGS re-measures the aquifer periodically by comparing water levels at thousands of wells against the same wells' historical readings.▸ Its most recent report, published in February 2024 by hydrologists Virginia McGuire and Kellan Strauch, put "recoverable water in storage" at about 2.91 billion acre-feet in 2019 — a decline of 286.4 million acre-feet, or roughly 10 percent, since predevelopment conditions around 1950. The area-weighted average water level across the whole aquifer has dropped 16.5 feet over that span, but the decline is not evenly spread. Texas and Kansas together account for 84 percent of the aquifer-wide loss — 169.6 million and 72.0 million acre-feet, respectively — while South Dakota is the only one of the eight states where storage has actually risen since predevelopment.

The bars above show magnitude of loss; South Dakota's +0.2 million acre-foot gain isn't pictured, but it's the one adjustment needed to reconcile the seven states' combined 286.6 million acre-foot decline with the USGS's stated aquifer-wide total of 286.4 million acre-feet.▸ Irrigated acreage across the whole footprint has followed a similar arc: from 2.1 million acres in 1949, it climbed to a peak of roughly 15.8 million acres in the mid-2000s and stood at 14.8 million acres in 2017 — the most recent year the report cites — covering about 14 percent of the land that overlies the aquifer.

Water under Kansas cropland doesn't trade on an open market the way corn or wheat does, so Nathan Hendricks and Gabriel Sampson, agricultural economists at Kansas State University, priced it indirectly: by comparing what buyers actually pay for irrigated versus otherwise identical dryland parcels.▸ Irrigated land in western Kansas sells for 53 percent more per acre than comparable dryland, their February 2022 study found, as reported by K-State's news service. Applied across the roughly 2.57 million irrigated acres in Kansas counties overlying the aquifer, at an assumed dryland baseline of $1,662 per acre, that premium adds up to $3.8 billion in land value that wouldn't exist without access to the Ogallala.

The same study puts a number on each foot of aquifer the county-level land market is watching disappear: a one-foot change in groundwater stock is associated with a $3-to-$15-per-acre change in irrigated land value.▸ Scaled across Kansas's irrigated acreage, one uniform foot of saturated thickness — gained or lost — is worth between $8 million and $41 million in aggregate land value.

Irrigation's footprint extends past land prices.▸ The same researchers found that Kansas counties overlying the aquifer post $2.4 billion more in annual animal sales, and carry 2.4 million more cattle on feed, than counties just outside it — and cited a 2013 USDA National Agricultural Statistics Service figure putting total agricultural sales from eight western Kansas counties overlying the aquifer at $4.7 billion, about a third of the state's entire farm revenue. Running the aquifer's own depletion projections forward, Hendricks and Sampson estimate that if current trends continue unchanged, Kansas's annual returns to irrigated land will fall by $34.1 million a year by 2050, compared to today — a standing bill for the feet of saturated thickness the state is projected to keep losing.

The $3.8 billion land-value figure, the $8-41 million per-foot range, and the $34.1 million 2050 projection all come from a single Kansas State University hedonic-pricing study covering irrigated counties in western Kansas. The 286.4 million acre-foot storage decline is a separate, aquifer-wide USGS measurement spanning all eight states. They are independent measurements of different but related things — one prices what's left in one state, the other measures what's gone across the whole aquifer — and shouldn't be read as components of a single total.