Water Quality and Possible Sources of Nitrogen and Bacteria to Rock and Travertine Creeks, Chickasaw National Recreation Area, Oklahoma, 2004

Becker, Carol

During the summer months, thousands of visitors swim and wade in the waters along Rock Creek and Travertine Creek in the Chickasaw National Recreation Area. The National Park Service reports that since 2001, Escherichia coli bacteria counts exceeding the Oklahoma primary contact standard of 235 colonies per 100 milliliters have been measured at swimming areas on Rock Creek and Travertine Creek during periods of high use, after heavy rainfall events, and during periods of extended drought. A better understanding of the potential sources of bacterial contamination to these streams would facilitate the development of strategies by the National Park Service officials to improve water quality. The U.S. Geological Survey, in cooperation with the National Park Service, conducted a study in the Upper Rock Creek basin in Murray County, Oklahoma during 2004. The objectives of the study were to identify the possible primary source(s) of Escherichia coli bacteria and related contaminants to surface water using: (1) analysis of nitrogen compounds and nitrogen-isotope ratios in nitrate nitrogen and ammonia nitrogen, (2) analysis of organic compounds associated with human wastewater, and (3) a genotypic method of bacterial source tracking. In May 2004, stream discharge and water properties were measured in addition to counts of fecal coliform and Escherichia coli bacteria at sites on Rock Creek and Travertine Creek. Surface water was sampled an additional three times at these locations during August and October. During those three sampling occasions, water properties and stream discharge were measured and samples were analyzed for nitrogen compounds and the stable nitrogen isotopes 15N and 14N in nitrate and ammonia nitrogen, and organic wastewater compounds. Fecal indicator bacteria were enumerated and surface water was collected to culture and isolate Escherichia coli bacteria for a bacterial source tracking technique described as ribotyping. The water quality of Rock Creek in the Chickasaw National Recreation Area seems to be affected most during periods of precipitation from surface-water runoff and sewage effluent. Fecal coliform and Escherichia coli bacteria counts in addition to ammonia nitrogen plus organic nitrogen and total nitrogen concentrations were highest in Rock Creek during the precipitation event on October 1. The increase of these constituents in surface water probably can be attributed in part to runoff containing fecal and organic material from non-point sources such as livestock grazing areas in the basin. The area of early runoff in the Rock Creek basin, downstream from the floodwater retarding structures and upstream from the Chickasaw National Recreation Area, may be an area of substantial non-point source contamination during precipitation events.