Preliminary Characterization of Thermal Waters East of Hot Springs National Park

Established in 1832 to preserve 47 hot springs flowing from of Hot Springs Mountain, Hot Springs National Park (HSNP) is the oldest National Park in the country. Recent findings show that the geologic formations constituting the geothermal system of HSNP actively support geothermal activity well east of the boundaries of HSNP. The Arkansas State Highway and Transportation Department plans to construct a four-lane highway bypass (approximately five miles in length) around the City of Hot Springs that would traverse the potential recharge area and involve blasting road cuts through a series of brittle novaculite ridges. In 2006, hot water was pumped from a local well located 5.5 miles east of the park and approximately one mile from the highway construction- the first known occurrence of geothermal waters outside the park in more than 175 years.

Sampling at spring.

The existence of the geothermal system east of the park highlights the potential vulnerability of the thermal water resource of HSNP to changes resulting from human activities. Potential impacts could include pirating of thermal flow from the current flow path that feeds the hot springs of HSNP, changes in hot springs discharge, and changes in hot springs temperature due to changing contribution ratios for hot-water and cold-water components.

Current U.S. Geological Survey activities for addressing the causes of thermal water outside of the HSNP boundaries include:

1. A survey reconnaissance of the existence and distribution of any other thermal waters outside of the HSNP in this eastern area around the hot well location.
2. Geophysical logging and discrete-zone geochemical sampling of thermal wells to characterize the geology, identifying geologic formation contacts, fracture zones, and other elements of site hydrogeology.
3. Water-level monitoring of selected wells to provide information on timing of head response to recharge events, which will serve to indicate change in the system and show connection between various components of the hydrologic system.
4. Geochemical and isotopic sampling of hot springs and wells in the recharge area to characterize the geochemistry and refine the recharge area for the hot springs.

Publications
	Scientific Investigations Report 2007-5004 Influence of locally derived recharge on the water quality and temperature of springs in Hot Springs National Park, Arkansas, by R.W. Bell and P.D. Hays
	Scientific Investigations Report 2006-5001 Characteristics of thermal springs and the shallow ground-water system at Hot Spring National Park, Arkansas, by D.S. Yeatts
	U.S. Geological Survey Professional Paper 1044-C The Waters of Hot Springs National Park, Arkansas - Their Nature and Origin, by M.S. Bedinger, F.J. Pearson, Jr., J.E. Reed, T.R. Sniegocki, and C.G. Stone