Status of Groundwater Levels and Storage Volume in the EquusFor an overview of USGS information products, including maps, imagery, and publications, visit http://store.usgs.gov.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Status of Groundwater Levels and Storage Volume in the Equus Beds Aquifer near Wichita, Kansas, January 2016By Brian J. Klager AbstractThe Equus Beds aquifer in south-central Kansas, which is part of the High Plains aquifer, serves as a source of water for municipal and agricultural users in the area. The city of Wichita has used the Equus Beds aquifer as one of its primary water sources since the 1940s. The aquifer in and around Wichita's well field reached historically low water levels in 1993, prompting the city to adopt new water-use and conservation strategies to ensure future water supply needs were met. Part of the plan was to initiate a managed aquifer recharge program called the Equus Beds Aquifer Storage and Recovery project. The goal of the managed aquifer recharge program is to artificially recharge the Equus Beds aquifer with treated water from the Little Arkansas River. As part of the Equus Beds Aquifer Storage and Recovery project, the city of Wichita and the U.S. Geological Survey have partnered in a long-term cooperative study to monitor and describe the quantity and quality of the water in the Equus Beds aquifer and the Little Arkansas River.The city of Wichita, the Equus Beds Groundwater Management District No. 2, the Kansas Department of Agriculture-Division of Water Resources, and the U.S. Geological Survey collected groundwater levels in numerous wells screened in the Equus Beds aquifer in the area in and around Wichita's well field in January 2016. The measurements were used to interpolate potentiometric surfaces for shallow and deep parts of the aquifer in the study area. These potentiometric surfaces were compared with potentiometric surfaces from previous years to estimate changes in water levels and storage volume in the study area.

To evaluate the magnitude of, and change in, miningrelated contamination, streambed-sediment samples were collected from 30 sampling sites in the Spring River Basin in the Cherokee County Superfund site, southeast Kansas, in July and August 2017. The Cherokee County Superfund site is part of the Tri-State Mining District, an area that covers parts of Kansas, Missouri, and Oklahoma that was historically mined for lead and zinc. The sampling sites corresponded to 30 sites sampled in 2004 as part of a previous study. Concentrations of cadmium, lead, and zinc in the 2017 streambed-sediment samples were compared with the 2004 concentrations and with available sediment-quality guidelines. Cadmium concentrations from 2004 and 2017 samples were not compared if both samples had concentrations less than the lower of the sediment-quality guidelines because of poor performance of cadmium replicate-samples analyses at lower concentrations. Streambed-sediment concentrations of cadmium, lead, and zinc in the 2017 samples compared to the 2004 samples were decreased by at least 20 percent at 12, 16, and 16 sites, respectively; increased by at least 20 percent at 2, 5, and 7 sites, respectively; and had less than a 20-percent change at 5, 9, and 7 sites, respectively. In 2017, cadmium, lead, and zinc concentrations exceeded general consensusbased sediment-quality guidelines at 17, 14, and 18 sites, respectively, compared to 19, 17, and 20 sites, respectively, in 2004. In 2017, cadmium, lead, and zinc concentrations exceeded Tri-State Mining District-specific sediment-quality guidelines at 12, 14, and 11 sites, respectively, compared to 16, 16, and 13 sites, respectively, in 2004. The highest 2017 concentrations of cadmium, lead, and zinc were measured at sites along Short Creek near Galena, Kansas.

Data were collected at two monitoring sites along the Little Arkansas River in south-central Kansas that bracket most of the easternmost part of the Equus Beds aquifer. The data were used as part of the city of Wichita's aquifer storage and recovery project to evaluate source water quality. The U.S. Geological Survey, in cooperation with the City of Wichita, has continued to monitor the water quality of these sites through 2019 to update previously published regressionbased models using continuously measured physicochemical properties and discretely sampled water-quality constituents of interest. The purpose of this report is to provide an update of the previously published linear regression models that have been used to continuously compute estimates of water-quality constituent concentrations or densities at these two sites. Water-quality constituent model updates include those for dissolved and suspended solids, suspended-sediment concentration, hardness, alkalinity, primary ions (bicarbonate, calcium, sodium, chloride, and sulfate), nutrients (total Kjeldahl nitrogen and total phosphorus), total organic carbon, indicator bacteria (Escherichia coli and fecal coliform bacteria), a trace element (arsenic), and a pesticide (atrazine).Regression analyses were used to develop surrogate models that related continuously measured physicochemical properties, streamflow, and seasonal components to discretely sampled water-quality constituent concentrations or densities. Specific conductance was an explanatory variable for dissolved solids, primary ions, and atrazine. Turbidity was an explanatory variable for total suspended solids and sediment, nutrients, total organic carbon, and indicator bacteria. Streamflow and water temperature were explanatory variables for dissolved arsenic. Seasonal components were included as explanatory variables for atrazine models. The amount of variance explained by most of the updated models was within 5 percent of previously published models.

No abstract

For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.