Water quality on the Little Arkansas River and in the Equus Beds aquifer has not substantially changed since 2007 recharge activities began in the Equus Beds aquifer, according to a new study by the U.S. Geological Survey, in cooperation with the City of Wichita, Kansas.

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The Equus Beds aquifer is one of the primary water-supply sources for the city of Wichita. Groundwater pumping for municipal and irrigation needs and sporadic drought conditions have caused water-level declines that led to concerns about the adequacy of the future water supply for Wichita. For this reason, the City of Wichita developed the Equus Beds Aquifer Storage and Recovery (ASR) project.

Scientists with the USGS looked at water-quality characteristics two years before (January 2011 through April 2013) and two years after (May 2013 through December 2014) Phase II of the aquifer recovery activities started. Researchers examined water chemistry, biology and habitat health on the Little Arkansas River, as well as the water quality of groundwater in the Equus Beds aquifer. Findings showed that the ASR did not substantially impact water quality. The full report is available online.

“This study shows that most of the small changes observed in surface and groundwater quality were largely governed by streamflow and precipitation, rather than activities related to the City of Wichita’s aquifer storage and recovery efforts,” said Scott Macey, City of Wichita Water Resource Engineer. “Understanding the condition of water resources adjacent to the recovery project allows Wichita to make informed water planning decisions.” 

In 2007, the City of Wichita began to artificially recharge the aquifer with treated storm runoff water from the Little Arkansas River or bank storage wells along the river. Phase II of the project started in 2013, which includes runoff being treated to meet drinking-water quality standards before recharging the aquifer through wells, or recharge basins. After the water is treated at a facility, the residuals, or what is removed from the water, are returned to the Little Arkansas River downstream of the facility in adherence to Kansas Department of Health requirements.

Study results show no significant differences in the quality of the Little Arkansas River upstream and downstream of the treatment facility after the ASR facility began operating. This finding is likely because the residuals are diluted by increased streamflow required for ASR facility operations to take place.

The health of aquatic biology was the same between upstream and downstream sites, according to Kansas Department of Health and Environment macroinvertebrate aquatic life support scores and fish community biotic integrity scores.

After the recharge program began, there was a small increase in concentrations of some water-quality constituents in the groundwater, including chloride, arsenic, phosphorus and carbon, but all were below drinking-water standard levels. Conversely, nitrate and some bacteria levels significantly decreased.

Artificial recharge is being used to increase water levels and storage volume in the aquifer to provide for water during drought conditions. Increased water levels can slow down the migration of a plume of chloride that is approaching the Wichita well field from historic oil and gas activities near Burrton, Kansas. The USGS will continue to work with the City of Wichita, the Equus Beds Groundwater Management District No. 2 and the Kansas Geological Survey to monitor the water-level and storage-volume changes in the Equus Beds aquifer.

More information is available on USGS efforts related to defining and understanding water quantity and quality of the Equus Beds aquifer on the USGS Kansas Water Science Center website.

The USGS provides information in a number of states related to preservation of water supplies in artificial recharge and aquifer storage and recovery. For more information visit the USGS artificial groundwater recharge website.

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