A recent publication by the Kansas Geological Survey (KGS) at the University of Kansas sheds light on the current conditions and trends in water levels and groundwater usage within the High Plains Aquifer (HPA) in Kansas, emphasizing the importance of sustainable management practices.
The HPA, a crucial groundwater resource spanning eight states from South Dakota to Texas, is pivotal in sustaining agriculture and communities, particularly in western Kansas, KGS said. It includes the Ogallala Aquifer of western Kansas and the Great Bend Prairie and Equus Beds aquifers in the south-central part of the state.
In the western portion of the state and within the Ogallala Aquifer are three groundwater management districts (GMDs): Western Kansas (GMD1), Southwest Kansas (GMD3) and Northwest Kansas (GMD4). In the south-central portion, the Big Bend (GMD5) and Equus Beds (GMD2) encompass the Great Bend Prairie and Equus Beds portions of the aquifer, respectively.
Water level and water use data from the last 25 years has enabled KGS to assess the aquifer’s status in Kansas thoroughly. During winter, KGS and the Division of Water Resources in the Kansas Department of Agriculture annually measure groundwater levels in approximately 1,400 wells, primarily irrigation wells. According to the publication titled “2023 Status of the High Plains Aquifer in Kansas,” Kansas has more than 35,600 wells with active water rights, with approximately 88% (24,179) used for irrigation in the HPA.
“The availability of more than 25 years’ worth of high-quality water-level and water-use data for the aquifer makes it possible to provide a sound assessment of the aquifer status,” said Donald Whittemore, KGS emeritus senior scientist and lead author of the publication. “The results can help irrigators, groundwater management districts, and other local and state agencies determine how successful conservation efforts have been.”
The publication highlights the potential for sustaining groundwater levels in imperiled areas of western Kansas by reducing pumping between 18-32%. Such reductions, defined as achieving zero water-level change, could extend the aquifer’s viability for at least one to two decades, KGS said. Groundwater levels in the Ogallala portion (GMDs 1, 3 and 4) have significantly declined since the widespread adoption of irrigation in the mid-20th century, leaving some areas with less than 40% of the original aquifer thickness. The publication states the average aquifer thicknesses remaining in GMDs 4, 1 and 3 are 75 feet, 32 feet and 142 feet, respectively.
Analysis of data from GMD1 in west-central Kansas and a portion of GMD4 in northwest Kansas reveals that water conservation measures have effectively slowed the rate of water use and water-level declines. By comparing water use before and after implementing conservation measures, researchers at KGS were able to determine the contributions of irrigation efficiency and decreases in irrigated areas to the overall reduction in pumping.
In Sheridan County in GMD4, the state’s first local enhanced management area (LEMA), known as the Sheridan-6 LEMA, realized water savings. LEMAs empower local stakeholders to develop plans for reducing irrigation pumping in specified areas, with oversight provided by groundwater management districts and the Kansas Department of Agriculture Division of Water Resources. Since its formation in 2013, it has achieved water savings of approximately 23%, attributed to irrigation efficiency, with an additional 1% related to a decrease in irrigated area.
While the Sheridan-6 LEMA has been a success story, the districtwide LEMA in GMD4, established in 2018, has not substantially impacted water use or water-level declines.
In GMD1, two LEMAs have been formed and led to a total reduction in pumping of about 24% districtwide, with 10.5% attributed to irrigation efficiency and nearly 14% to decreases in irrigated acreage. Wichita County, which formed a LEMA in 2021, stands out with a reduction in pumping of about 40% due to adjustments by farmers, such as reducing acreage, altering cropping patterns and adopting technologies to optimize water usage.
In south-central Kansas, the Equus Beds Aquifer in GMD2 has demonstrated stable water levels over the past 25 years, while the GMD5 Big Bend Prairie region shows a slight decline. The necessary reduction in pumping to achieve districtwide stable water levels in GMD5 is estimated at 1.6%.
“Our results show that the only way to slow water-level declines is to reduce pumping in conjunction with modification of agricultural practices,” said Jim Butler, KGS senior scientist and one of the report’s co-authors. “Use of more efficient irrigation technology by itself will not slow these declines. As has been shown in Kansas and elsewhere, efficient irrigation technology must be coupled with a binding agreement to reduce pumping if we are to make a difference.” — Charles Wallace, WLJ contributing editor
