GROUNDWATER FLOW ESTIMATION USING T-Z PROFILES IN A COMPLEX ENVIRONMENT WITH A CHANGING CLIMATE (Invited Presentation)

Obtaining estimates of vertical groundwater flows remains a challenge in hydrogeology. A number of methods based on temperature-depth (T-z) profiles are available to provide vertical groundwater flow estimates. However, methods based on steady state assumptions have been shown to be inappropriate for sites that have experienced land surface warming. Analytical solutions that account for surface warming are available, however they typically include unrealistic or restrictive assumptions, e.g. no flow initial conditions, or linear surface warming. We use a new analytical solution and associated computer program (FAST) that provides flexible initial and boundary conditions to estimate fluxes using T-z profiles from the “Willunga Super Science Site”, a complex, but densely instrumented site in South Australia. T-z profiles from eight wells (ranging from high elevation to near sea level) were utilized, in addition to mean air temperatures at nearby weather stations (boundary conditions), and down borehole geophysics to estimate thermal properties. Temperature based flux estimates were on the order of those estimated using chloride mass balance, providing a useful approach to constrain flux estimates utilizing data from non-hydraulic sources.