Last year, when researchers from the Kansas Geological Survey traveled to western Kansas to measure groundwater levels in the High Plains Aquifer, they found those levels had dropped by an average of about three and a half feet.

It was the second largest single-year decline they had ever recorded, exceeded only by the one the year before, when water tables had fallen an average of 4.25 feet.

Now those researchers are preparing to head out again for another round of measurements, and they don’t expect to see any change in those trends.

“I’ve only been doing this about eight years, and historically it’s declined year after year,” said Brett Wedel, manager of the KGS water-level-data acquisition program. “Some areas are worse than others. Two years ago was definitely the most drastic drop I’ve seen.”

Weather permitting, KGS crews and the Kansas Division of Water Resources plan to measure 1,407 wells in the aquifer region of central and western Kansas this winter, from Colby and Goodland in the north, down to Liberal and Garden City in the south.

Most of the wells draw water from the High Plains aquifer, a large network of underground water-bearing rocks that stretches from South Dakota and Wyoming to Texas and New Mexico. It includes the Ogallala aquifer in western Kansas, the Great Bend Prairie aquifer in west-central Kansas, and the Equus Beds aquifer north and west of Wichita.

That system is the primary source of water for cities and industries in the area. But the heaviest demand by far for the water is agriculture, which was fundamentally transformed in that region with the invention in 1948 of center-pivot irrigation, those devices that create large circular crop fields in an otherwise flat and grid-like landscape.

Over roughly the past five years, an extended drought in the central plains has forced farmers there to rely even more heavily on irrigation, drawing down two to three feet of water each year, while nature replaces only a few inches per year.

“Although parts of west-central and southwest Kansas received significant precipitation amounts in late July and August 2013, drought conditions persisted across roughly the western third of the state,” KGS water-data manager Brownie Wilson said. “Most of northwest Kansas missed out on those rains.”

Data collected during the annual survey are intended to help landowners and other water users evaluate local trends and plan for managing groundwater resources.

But most people acknowledge that those management plans will only buy time, and unless farming practices in the region change dramatically – or until the weather does – water in the aquifer is a finite resource.

“At some point it no longer becomes a continual process,” Wedel said. “You’re going to eventually bleed that resource dry.”