HESS Hydrology and Earth System Sciences HESS Hydrol. Earth Syst. Sci. 1607-7938 Copernicus Publications Göttingen, Germany 10.5194/hess-19-137-2015 Thermal damping and retardation in karst conduits Luhmann A. J. 1 Covington M. D. https://orcid.org/0000-0003-4044-7387 2 Myre J. M. 2 Perne M. 3 2 Jones S. W. 4 Alexander Jr. E. C. 1 Saar M. O. 1 5 University of Minnesota, Department of Earth Sciences, 310 Pillsbury Dr. SE, Minneapolis, Minnesota 55455, USA University of Arkansas, Department of Geosciences, 216 Ozark Hall, Fayetteville, Arkansas 72701, USA Jožef Stefan Institute, Department of Systems and Control, Jamova Cesta 39, Ljubljana, Slovenia 527 Karrow St., Maryville, Tennessee 37803, USA ETH-Zürich, Geothermal Energy and Geofluids Group, Department of Earth Sciences, Zürich, Switzerland 09 01 2015 19 1 137 157 Copyright: © 2015 A. J. Luhmann et al. 2015 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://hess.copernicus.org/articles/19/137/2015/hess-19-137-2015.html The full text article is available as a PDF file from https://hess.copernicus.org/articles/19/137/2015/hess-19-137-2015.pdf

Water temperature is a non-conservative tracer in the environment. Variations in recharge temperature are damped and retarded as water moves through an aquifer due to heat exchange between water and rock. However, within karst aquifers, seasonal and short-term fluctuations in recharge temperature are often transmitted over long distances before they are fully damped. Using analytical solutions and numerical simulations, we develop relationships that describe the effect of flow path properties, flow-through time, recharge characteristics, and water and rock physical properties on the damping and retardation of thermal peaks/troughs in karst conduits. Using these relationships, one can estimate the thermal retardation and damping that would occur under given conditions with a given conduit geometry. Ultimately, these relationships can be used with thermal damping and retardation field data to estimate parameters such as conduit diameter. We also examine sets of numerical simulations where we relax some of the assumptions used to develop these relationships, testing the effects of variable diameter, variable velocity, open channels, and recharge shape on thermal damping and retardation to provide some constraints on uncertainty. Finally, we discuss a multitracer experiment that provides some field confirmation of our relationships. High temporal resolution water temperature data are required to obtain sufficient constraints on the magnitude and timing of thermal peaks and troughs in order to take full advantage of water temperature as a tracer.

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