Measuring Flow Rates and Characterization Flow Regimes in Hot Springs

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Kinetics, Geochemistry, hot springs, hydrothermal, degassing, Dissolved Oxygen, gypsum, turbulence, Yellowstone National Park


Detailed studies were conducted at Big Boiler hot spring in Lassen Volcanic National Park, CA, and Ojo Caliente hot spring in Yellowstone National Park, WY, to measure the flow rate and characterize the flow regime of hot spring drainages. These drainages represent some of the most dynamic interfaces between the hydrosphere and atmosphere with steep temperature gradients and chemical gradients. The rate of thermal disequilibrium and chemical disequilibrium dissipation depends on the flow rate and flow regime. The drainage of each hot spring was divided into ten or more segments and water samples were collected at segment boundaries. Fluid flow velocity throughout the drainage was measured using an in situ flow probe where possible and by determining the advancement of a red food dye tracer through the flow channel. A combination of field and laboratory studies was used to adapt a method based on the transport-controlled dissolution rate of gypsum to characterize the flow regime throughout the drainages. Laboratory experiments as a well as a deployment in an artificial drainage were conducted to validate the application of this method for hot spring environments. The deployment of the gypsum tablets was complemented by using digital videography to record the nature of the flow regime throughout the drainages. In situ flow probe measurements were not possible at all locations. The data obtained with the probe showed a range of values that was in reasonable agreement with the flow rates obtained using the dye tracer. The average flow rate based on advancement of dye tracer determined at Big Boiler was 0.22 m/s in both 2000 and 2001, while in Ojo Caliente flow rate varied from 0.39 m/s in 2001 to 0.45 m/s in 2002. The results of the gypsum dissolution measurement in the field yield boundary layer thicknesses between 8 and 38 micron, with most values between 15 and 25 micron, indicating well-developed turbulent flow throughout the drainages. The results, consistent with videography, indicate that gypsum dissolution rates based on the deployment of well-characterized and pure gypsum tablets can be used in hot-spring environments. An analysis of cooling rates within the drainages illustrates the importance of turbulent flow in cooling the waters.


Special Issue for Dr. Kirk Nordstrom