photo by: Contributed

The KGS and its research partners recently completed an airborne survey in northwestern Kansas to help get data from the High Plains aquifer.

Updated at 9:23 a.m. Monday, Aug. 19

As you fly over central and western Kansas, you’ll notice distinctive circles in the agricultural fields below.

Some might interpret these patterns as evidence of extraterrestrial activity, but researchers from the Kansas Geological Survey see them as indicators of one of the nation’s most important water resources at work nourishing crops across the landscape.

These circles are center-pivot irrigation systems, which are large sprinklers on wheels that move across fields. They allow for efficient irrigation on uneven terrain, but also support large-scale water pumping from the High Plains aquifer, spanning roughly 174,000 square miles across eight states.

The aquifer provides water for industry and tap water for municipalities like Colby along Interstate 70 in northwestern Kansas. However, most of the water is used for agricultural irrigation. Since these practices began around 1950, the water level has fallen by an average of 14.2 feet. In some areas of the Ogallala portion of the High Plains aquifer, the decline has surpassed 60%.

In recent months, residents of northwestern Kansas have looked up in surprise, wondering if they were seeing something else otherworldly. It was a low-flying helicopter carrying a large hexagonal frame, and it was doing an airborne survey throughout Kansas Groundwater Management District No. 4, one of five groundwater management districts.

The survey was conducted by the KGS to evaluate the Ogallala aquifer as part of a broader effort to measure geologic structures and groundwater conditions in the region.

photo by: Google Earth screenshot

These circles, which can be seen in Google Earth and from an airplane, are center-pivot irrigation systems. These systems are large sprinklers on wheels that move across fields.

“(These) significant water declines (are) making it very difficult, in some of these areas, to continue irrigated agriculture, and there are ramifications for all these rural communities that depend on the agricultural economy and it makes it a lot tougher,” said KGS senior scientist and project lead Jim Butler.

“This is what motivates us to explore the aquifer to see if there are more sustainable paths forward, and to be able to start defining those paths, we need to have a better understanding of aquifer conditions at a level of detail that we don’t currently have,” Butler said.

The funding for this project was provided by the governor’s office and the Kansas Water Office. The KGS and District No. 4 enlisted Aqua Geo Frameworks LLC of Fort Laramie, Wyoming, to be the general contractor and provide the initial analysis of the data.

Although other states like Nebraska, Colorado and Wyoming have conducted surveys covering over 20,000 miles of the High Plains aquifer, this is the first airborne survey of Kansas’ portion. These areas in Kansas are essential for understanding how to replenish the depleting aquifer.

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Running low on water

The High Plains aquifer — which includes the prominent Ogallala aquifer — provides 70% to 80% of the water used each day by western and central Kansas residents, acting as a crucial water source for the region. However, extensive pumping from this aquifer has caused water levels to drop significantly in the west, leading to a range of critical water-related challenges.

With the high demand for water growing, people continued to extract water from the aquifer thinking there was an inexhaustible supply underneath. This has led to declines in the water table, which is a saturated area of water-filled soil on the upper surface of an aquifer.

photo by: Contributed

The Arkansas River near Larned has dried up from extensive pumping of the High Plains aquifer.

For some areas, the aquifer could run out in only a couple of dozen years. Thomas County, home to Colby, is expected to run out of water in the Ogallala aquifer in less than 75 years, Butler said.

And all that pumping can have other effects that people might not expect. According to information on the KGS’ website, lower water levels in the aquifer mean more water from the Arkansas River seeping into the ground rather than continuing downstream.

The Arkansas River once flowed through Dodge City but has dried up in many areas due to long-term pumping. Some river sections can’t be replenished as easily because aquifers don’t have uniform water depths and natural recharge from rain is low because much of the rain falls during the growing season. Butler said he has been working at a dried-up area of the river close to Garden City since late 2001.

“(Now what’s left) is the sand and gravel over which the water used to flow,” Butler said. “This is what you consider as hydrologic collateral damage of the aquifer depletion in western Kansas.”

Researchers have measured water extraction from the High Plains aquifer using acre-feet, which is the volume of water needed to cover one acre of land to a depth of one foot. One acre-foot equals 325,851 gallons of water. Between 2012 and 2021, over 3 million acre-feet of water was withdrawn from the aquifer, with 2.3 million acre-feet coming from the Ogallala region.

A survey of what lies beneath the surface

The airborne survey, although conducted from 100 to 200 feet above the ground, provides resistivity measurements that reveal rock types and other materials up to 1,000 feet underground.

The frame mounted on the helicopter uses pulses of electric current to create a magnetic field that can be used to measure the resistivity below the surface. Sands and gravels – which are excellent aquifer materials that readily supply water to wells – exhibit high resistivity. In contrast, clays, silts and shales provide minimal water to wells and have low resistivity.

These measurements will reveal how sand and gravel intervals are distributed in the aquifer and how less-permeable materials affect its response to pumping. The survey will offer insight into the geological factors influencing well distribution and yield which are shaping the future of the aquifer in District No. 4.

Alongside the reconnaissance flight lines that offered a broad overview of aquifer conditions, the research team selected certain areas within District No. 4 for more detailed study using closely spaced flight lines. Notably, the Sheridan-6 Local Enhancement Area, a groundwater conservation zone established in 2013 in Sheridan County because of significant aquifer depletion, was identified as a key area of interest.

photo by: Contributed

The frame mounted on the helicopter collects electromagnetic data by sending pulses of current through it. These pulses create a primary magnetic field, which induces eddy currents in the ground, resulting in a secondary magnetic field. This secondary field provides information about the subsurface resistivity, which reveals rock types and other materials up to 1,000 feet underground, and this is the data KGS aims to gather.

The helicopter carrying the hexagonal frame flew for 2,443 miles over portions of Cheyenne, Sherman, Wallace, Rawlins, Thomas, Decatur and Sheridan counties from May 28 to its final flight on June 16. Its nearly month-long journey did not involve flying over residential areas, other buildings, livestock feeding operations or wind turbines, and it won’t in the future. To avoid any conspiracy theories arising, KGS researchers were determined to get the word out about this large device flying around northwestern Kansas.

“We worked with (District No. 4), and they sent out a postcard across to all the irrigators in the area telling them what was going to be done,” Butler said. “I can only imagine people looking up and being like, ‘what kind of alien contraption?'”

Saving the High Plains aquifer

Butler said that Kansas stands out because it tracks data that other states don’t, specifically water pumping. Nearly all non-domestic wells in Kansas are equipped with totalizing flow meters that record the volume of water pumped. This data allows KGS researchers to analyze the information and determine the necessary reduction in pumping to sustain the aquifer.

In a previous assessment published by the KGS and co-authored by Butler, researchers found that groundwater levels in the High Plains aquifer could be maintained for at least a decade in moisture-stressed regions of western Kansas by reducing pumping by 18% to 32%.

photo by: Contributed

Center-pivot irrigation systems can span half a mile in diameter. These systems pump a significant amount of water to irrigate crops.

To slow the decline in water levels, Butler emphasized the need to cut back on pumping and adjust agricultural practices. Improving irrigation efficiency is important, but for a significant impact, a binding agreement to reduce pumping is also necessary.

Butler said that although offering subsidies or grants for more efficient irrigation equipment seems like a promising solution, it hasn’t actually improved water conservation. In reality, giving farmers better equipment often just encourages them to grow more crops and use more water.

“The only way irrigation efficiency improvements will work is if it’s tied to a legally binding agreement to reduce water use,” Butler said. “Otherwise, if you don’t have that agreement, nothing happens.”

Next steps for the survey

Butler said he has already received preliminary data from the survey of the aquifer, but the final data won’t be released until sometime in November. The KGS and Stanford University will work closely together to analyze and present this data.

But they aren’t done yet. The KGS and Aqua Geo Frameworks are planning to carry out a similar survey of Western Kansas Groundwater Management District No. 1 in the summer of 2025. This district includes parts of Greeley, Lane, Scott, Wallace, and Wichita counties. If funding permits in subsequent years, the research team also intends to survey District 3 in 2026, which encompasses Finney, Ford, Grant, Hamilton, Haskell, Kearny, Meade, Morton, Seward, Stanton, and Stevens counties.

photo by: Contributed

The map shows the percent change of the High Plains aquifer’s thickness throughout western and central Kansas. The blue areas of the map indicate where the aquifer has increased in thickness since the widespread pumping of irrigated agriculture, which the dark red areas display areas where over 60% of the aquifer is gone.

“We will have a much better understanding of the composition of the aquifer,” Butler said. “And so we’re going to significantly reduce the uncertainty associated with our description of the aquifer in these models, and that, in turn, will lead to more reliable predictions of what the impact of certain management options will be.”

He said with that understanding, the KGS can work with regulatory agencies and irrigators to devise plans for extending the lifespan of the aquifer, which is their ultimate goal.

“We’ve got climate change lurking on the horizon there, so we need to get on this so we can be prepared,” Butler said. “I (will) have a better idea of what’s going on and be able to define paths forward that take into account likely climatic trajectories in terms of the conditions that will be faced out there.”

Editor’s note: This story has been corrected in two ways. The photo of the Kansas River was taken near Larned. Thomas County, home to Colby, is expected to run out of water in the Ogallala aquifer in less than 75 years, Butler said.