Box 7 Heat Transport Modeling
Analytical and numerical models are used to estimate flux rates from observed temperatures (e.g. Stallman, 1965; Goto et al., 2005; Hatch et al., 2006; Keery et al., 2007; Schmidt et al., 2007; Lien and Ford, 2014). Modeling requires assigning sediment thermal properties, estimates of porosity, measurements of VHG in the porous media, and assignment of thermal boundary conditions. The model calculates groundwater flux and groundwater velocities based on field-observed heat transport data sets. Stonestrom and Constantz (2004), Anderson (2005), and Constantz (2008) present tables of sediment thermal properties. VS2DH is widely used for such modeling. It is a public-domain, numerical, one-dimensional, energy transport and fluid flow simulator that can evaluate variably saturated flow and solute transport (Healy and Ronan, 1996). Other codes used for this purpose include Ex-Stream (Swanson and Cardenas, 2011) which uses MATLAB (Mathworks, Inc., and VFLUX (Gordon et al,. 2012). All three of these models simulate one-dimensional vertical flow. Two- and three-dimensional transport certainly occurs in some settings and the application of a simple one-dimensional model may be inappropriate (e.g., Cuthbert and Mckay, 2013).