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Estimation of subsurface flow from high-resolution temperature profiles
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  • Bo Zhang,
  • Kai Gu,
  • Peter Bayer,
  • Bin Shi,
  • Fulin Xiang,
  • Zhuang Wei,
  • Baojun Wang
Bo Zhang
Nanjing University

Corresponding Author:[email protected]

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Kai Gu
Nanjing University
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Peter Bayer
Martin Luther University Halle Wittenberg
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Bin Shi
Nanjing University
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Fulin Xiang
Nanjing University
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Zhuang Wei
Nanjing University
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Baojun Wang
Nanjing University
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Abstract

Subsurface flow rates are critical for hydrology and geothermal research, while field characterization remains a challenge. There are several analytical solutions for calculating the vertical water flux based on measured temperatures. Heat is a popular natural tracer to estimate subsurface flow rates. However, quantifying flow rates is impeded by insufficient sensors spacing during field investigations or simplifying assumptions for analysis such as sinusoidal temperature boundary. The objective of this study is to develop a convenient method to investigate subsurface flow on the sub-meter scale. Here, we present a program to estimate water fluxes based on temperature-depth profiles, so-called TempFlow. TempFlow is a numerical program written in MATLAB that calculates steady state flow in transient heat tracing based on the inversion of measured high-resolution temperature-depth series observed at a certain time. In this program, the Fiber Optic Distributed Temperature Sensing (FO-DTS) is recommended for temperature collection. FO-DTS techniques provide high-resolution temperature measurements with continuous temperature profiles that account for sub-meter scale and nonperiodic boundary conditions in saturated sediments. The estimated subsurface flow using TempFlow was validated in a medium-scale tank with a series of experiments, where the hydraulic and temperature boundary conditions were well-controlled. The results indicate that the estimation using TempFlow obtained similar results as the experiments. Thus, the method could potentially be used to determine the flow rate of the subsurface.