ANALYTICAL MODELING OF HEAT FLUX AND SUBSURFACE FLOWPATHS USING SHALLOW SEISMIC REFRACTION AND GROUND TEMPERATURES AT BURGDORF HOT SPRINGS, IDAHO

Burgdorf Hot Springs is a recreational bathing resort located in the Payette National Forest north of McCall, Idaho. We conducted a shallow seismic refraction survey and measured near-surface ground temperatures to estimate overburden thickness and isolate subsurface flowpaths near the spring discharge area. Our data indicate upwelling of hydrothermal fluids, probably from fractures in the granite bedrock, and subsequent lateral flow along the bedrock/alluvium contact to the discharge point that feeds the recreational pools. We used Poisson's equation to model steady-state heat losses from the hydrothermal fluids to the land surface as a function of distance from the presumed source in the granite fractures, and attempted to calibrate the model using the measured shallow ground temperatures. The results of this study offer the potential to calculate temperatures of the upwelling fluids at the granite/alluvium interface, and may assist with the development of plans for direct use of the hydrothermal fluids.