The city of Wichita artificially recharged about 1 billion gallons of water into the Equus Beds aquifer during 2007–2012 as part of Phase I recharge of the Artificial Storage and Recovery project. This report, prepared in cooperation by the U.S. Geological Survey and the city of Wichita, Kansas, summarizes Little Arkansas River (source-water for artificial recharge) andEquus Beds aquifer water quality before (1995–2006) and during (2007–2012) Artificial Storage and Recovery Phase I recharge. Additionally, aquifer water-quality distribution maps are presented and water-quality changes associated with Phase I recharge timing are described.

Computed chloride concentrations in the Little Arkansas River exceeded the Federal secondary maximum contaminant level (SMCL) about 20 percent of the time during 1999 through 2012, primarily during low-flow conditions. Groundwater chloride concentrations during 2001 through 2012 exceeded the SMCL in about 6 percent of shallow wells and 7 percent of deep wells, primarily near Burrton, Kansas and along the Arkansas River. Nearly all surface water nitrate plus nitrite concentrations during 1995 through 2012 were less than the Federal maximum contaminant level (MCL); groundwater nitrate plus nitrite concentrations exceeded the MCL in about 16 percent of shallow groundwater samples and were minimal in the deeper parts of the aquifer. Several trace elements frequently exceeded drinking water criteria, including arsenic, iron, and manganese.

Recharge activities at Phase I recharge wells have not resulted in substantial effects on groundwater quality in the area, likely because the total amount of water recharged is relatively small (1 billion gallons) compared to aquifer storage volume (greater than 990 billion gallons in winter 2012). The eastward movement of the Burrton chloride plume is likely being slowed by a line of recharge locations associated with Phase I; however, chloride concentrations in deep groundwater still advanced to less than one half mile from the central part of the study area. Water-quality constituents of concern (major ions, nutrients, trace elements, triazine herbicides, and fecal indicator bacteria) have not increased substantially and are likely more affected by climatological (natural recharge by precipitation) and natural (geochemical oxidation/reduction, metabolic and decay rates) processes than artificial recharge. Arsenic remains a water-quality constituent of concern because of natural and continued persistence of concentrations exceeding the Federal maximum contaminant level of 10 micrograms per liter, especially in the deeper parts of theEquus Beds aquifer.