Effects of Artificial Recharge on Water Quality in the Equus Beds Aquifer, South-Central Kansas

By Andrew C. Ziegler and Heather C. Ross
U.S. Geological Survey, 4821 Quail Crest Place, Lawrence, Kansas 66049

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Abstract

Water for 400,000 Wichita area residents comes from Cheney Reservoir (a large Federal impoundment) and a well field in the Equus Beds aquifer in south-central Kansas. These sources are not expected to meet the projected water needs for Wichita into the 21st century. One alternative being investigated to help meet future water-supply demands for the city is artificial recharge of the aquifer in the well field area using high flows from the Little Arkansas River. This process may have an added benefit of preventing degradation of the aquifer from existing chloride plumes migrating toward the well field from a nearby oil field and from the Arkansas River.

From 1995 to 2000, more than 4,000 samples were collected from the Little Arkansas River, wells in the area, and monitoring wells at test sites in the well field area before and after an artificial recharge demonstration project began.  Water samples were analyzed for more than 400 chemicals and bacteria. In samples collected before recharge, current (2001) U.S. Environmental Protection Agency (USEPA) drinking-water standards were exceeded for chloride, atrazine, and total coliform bacteria in surface-water samples and for arsenic in recharge water and one monitoring well at one of the test sites (Halstead).

Since artificial recharge began in 1997, there have been minimal effects on the quality of the existing ground water after recharging more than 1 billion gallons of water (5 percent of Wichita's annual water needs). After artificial recharge began, median concentrations of more than 400 chemicals including chloride, atrazine, and total coliform bacteria were all substantially less than their respective drinking-water standards and similar to concentrations in the receiving ground water before recharge. However, arsenic concentrations in the one monitoring well at the test site near Halstead increased from 8 to 19 micrograms per liter and exceeded the new (2001) USEPA drinking-water standard of 10 micrograms per liter. Continued monitoring of recharge and ground water will help prevent degradation of the water-quality in the Equus Beds aquifer. Current monitoring and interpretative information are available on the Internet at http://ks.water.usgs.gov/Kansas/studies/equus/.

In George R. Aiken and Eve L. Kuniansky, editors, 2002, U.S. Geological Survey Artificial Recharge Workshop Proceedings, Sacramento, California, April 2-4, 2002: USGS Open-File Report 02-89

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