Temperature-driven groundwater convection in cold climates

Abstract

The aim was to study density-driven groundwater flow and analyse groundwater mixing because of seasonal changes in groundwater temperature. Here, density-driven convection in groundwater was studied by numerical simulations in a subarctic climate, i.e. where the water temperature was <4°C. The effects of soil permeability and groundwater temperature (i.e. viscosity and density) were determined. The influence of impermeable obstacles in otherwise homogeneous ground was also studied. An initial disturbance in the form of a horizontal groundwater flow was necessary to start the convection. Transient solutions describe the development of convective cells in the groundwater and it took 22 days before fully developed convection patterns were formed. The thermal convection reached a maximum depth of 1.0 m in soil of low permeability (2.71 · 10 −9 m 2 ). At groundwater temperature close to its density maximum (4°C), the physical size (in m) of the convection cells was reduced. Small stones or frost lenses in the ground slightly affect the convective flow, while larger obstacles change the size and shape of the convection cells. Performed simulations show that Bseasonal groundwater turnover^occurs. This knowledge may be useful in the prevention of nutrient leakage to underlying groundwater from soils, especially in agricultural areas where no natural vertical groundwater flow is evident. An application in northern Sweden is discussed.

Minimizing Virus Transport in Porous Media by Optimizing Solid Phase Inactivation

“…Seasonal temperature variations initiate and drive thermal groundwater convection, especially during the transition from summer to winter months (Engström and Nordell, 2016). In natural systems, thermally driven convection is initiated by various processes such as varying groundwater flow and infiltration of rain and Table 1, Supplemental Table S1, and Table 2 present fitted model parameters, standard error coefficient, and mass balance information, respectively.…”

Single‐Rate Dual‐Domain Mass Transfer Model: Elucidating Temperature Effects

“…For instance, the transport of solutes in porous media can be modified by the ambient temperature in the subsurface. Here, documented examples include, among others, temperature impacts on the groundwater flow regime in the form of buoyancy effects and variations of the hydraulic conductivity value (e.g., Engström & Nordell, 2016; Harris et al., 2015; Ma & Zheng, 2010). Furthermore, chemical reaction rates (e.g., Brielmann et al., 2009; Prommer & Stuyfzand, 2005; Saripalli et al., 2001), (micro) biological activity (e.g., Derx et al., 2012; Gharabaghi et al., 2015; Stein et al., 2006) as well as intensity of diffusive processes (e.g., Mon et al., 2016) typically correlate with changes in ambient temperature.…”

Seawater intrusion in coastal aquifers: Combined effects of salinity and temperature

“…In groundwater studies, the effect of heat and salt on the pore water flow due to natural convection has been studied typically separately, except for the class of double-diffusive convection as will be reviewed in more detail in the next section. While the salinity effect features extensively in the groundwater dynamics in coastal aquifers as previously discussed, heat transport has also been studied comprehensively for distribution tendency, controlling parameters and effect on pore water flow [Elder, 1967;Straus and Schubert, 1977;Molson et al, 1992;Ferguson, 2007;Van Lopik et al, 2015;Engström and Nordell, 2016]. Mechanistically, heat transport in porous media results from a combination of the convection associated with fluid flow and the thermal conduction through both fluid and the solid matrix [Engström and Nordell, 2016].…”

“…While the salinity effect features extensively in the groundwater dynamics in coastal aquifers as previously discussed, heat transport has also been studied comprehensively for distribution tendency, controlling parameters and effect on pore water flow [Elder, 1967;Straus and Schubert, 1977;Molson et al, 1992;Ferguson, 2007;Van Lopik et al, 2015;Engström and Nordell, 2016]. Mechanistically, heat transport in porous media results from a combination of the convection associated with fluid flow and the thermal conduction through both fluid and the solid matrix [Engström and Nordell, 2016]. Kilty and Chapman [1980] supported the consideration of groundwater movement in assessment of subsurface temperature distribution after employing convective heat transfer theory to elaborate the thermal anomalies under three different field conditions.…”