LAWRENCE — In 2013 average groundwater levels in central Kansas rose for the first time in four years while levels in western Kansas continued to decline, although less sharply than in 2012, according to preliminary data compiled by the Kansas Geological Survey, based at the University of Kansas.
The KGS and the Division of Water Resources of the Kansas Department of Agriculture measured groundwater level in approximately 1,400 water wells in early 2014 as part of a program to monitor the health and sustainability of the state’s most important groundwater resources.
Between January 2012 and January 2013, the well network on the whole averaged a water-level decline of about 0.9 feet, although results varied significantly across the network. In the Equus Beds — a major source of water for Wichita, Hutchinson and surrounding towns — average levels rose more than 2.5 feet. In southwestern Kansas, average levels dropped about 2.3 feet.
The KGS measures approximately 500 wells in western Kansas each January, and DWR staff from field offices in Stockton, Garden City and Stafford measure nearly 900 in western and central Kansas. Most of the wells are used for irrigation and have been measured since at least 1996.
The same wells, spread over 47 counties, are measured every year to determine the long-term behavior of the High Plains aquifer system — a network of underground water-bearing formations, consisting of porous rock and unconsolidated sediment that includes the Equus Beds and Great Bend Prairie aquifer in south-central Kansas and the expansive Ogallala aquifer.
Measurements are taken primarily in January because water levels are least likely to fluctuate when irrigation wells aren’t in use. Infrequently, however, later-than-normal pumping due to dry conditions may unduly affect measurement results.
Ninety percent of the wells measured by the KGS and DWR draw from the High Plains aquifer, the primary source of irrigation, municipal and industrial water for much of western and central Kansas. Other measured wells tap the deeper Dakota system or shallower alluvial aquifers along streams and rivers.
Above-average precipitation in July and August led to the gains in central Kansas and slowed losses in much of western Kansas.
“July and August saw some very high rainfall amounts across south-central Kansas, west-central Kansas and even into portions of drought-stricken southwest Kansas,” said Brownie Wilson, KGS water-data manager. “Obviously, any time you can get your water demands satisfied by Mother Nature, the less you have to pull from aquifers and surface reservoirs.”
During dry periods, the prolonged pumping to compensate for the lack of precipitation, not the lack of precipitation itself, has the biggest impact on groundwater levels, he said.
Much of south-central Kansas also received above-average rainfall in April and May, lowering the demand for irrigation water during the growing season.
Besides receiving more precipitation, on average, than western Kansas, south-central Kansas also has geologic advantages. Groundwater there is relatively close to the surface and often overlain by sandy soils that allow some recharge to reach the aquifer, while farther west the water is deeper and more confined beneath less penetrable rocks.
Despite above average rainfall throughout much of the state in midsummer, dry conditions persisted in western Kansas during the prime growing season. Much of southwestern Kansas, for example, received less than 50 percent — in many places less then 25 percent — of normal precipitation between March and early June.
“It’s tough to catch up when that happens,” Wilson said.
Most of the 1,400 wells in the network monitored by KGS and DWR are within the boundaries of the state’s five Groundwater Management Districts (GMDs), which are organized and governed by area landowners and large-scale water users to address water-resource issues.
In southwestern Kansas GMD 3, levels dropped 2.31 feet in 2013, after declining 3.10 feet, 3.70 feet and 3.60 feet in the three previous years, respectively. Since 1996, when the monitoring program began, groundwater levels in the area have dropped, on average, nearly 35 feet.
The wells monitored in GMD 3 pull water from the Ogallala aquifer except in a few areas where they draw from the Dakota aquifer. The district includes all or part of Grant, Haskell, Gray, Finney, Stanton, Ford, Morton, Stevens, Seward, Hamilton, Kearny and Meade counties.
Western Kansas GMD 1 includes portions of Wallace, Greeley, Wichita, Scott and Lane counties, where the majority of wells are drilled into the Ogallala aquifer. In GMD 1, groundwater levels declined 0.79 feet in 2013 compared to 1.27 in 2011 and 1.66 feet in 2012.
Water levels in northwest Kansas GMD 4 declined, on average, 0.76 feet during 2013. Although declines were not as great as in 2012, when the average level fell 1.39 feet, GMD 4 missed out on the above-average precipitation experienced across much of the rest of western Kansas in July and August.
GMD 4 covers Sherman, Thomas and Sheridan, and parts of Cheyenne, Rawlins, Decatur, Graham, Wallace, Logan and Gove counties. Groundwater there is pumped mainly from the Ogallala aquifer.
Big Bend GMD 5, centered on the Great Bend Prairie aquifer underlying Stafford and Pratt counties and parts of Barton, Pawnee, Edwards, Kiowa, Reno and Rice counties, had a 0.55-foot water-level increase overall, with a rise of more than 2 feet in the eastern half. Levels in GMD 5 fell 2.86 feet in 2011 and 1.86 feet in 2012.
Equus Bed GMD 2 includes parts of Sedgwick, McPherson, Harvey and Reno counties. Groundwater levels there rose 2.57 feet after declining 3.07 feet in 2011 and 1.64 feet in 2012.
Measurement results are provisional and subject to revision based on additional analysis. The data is scheduled to be available in late February online.