title: Groundwater flow estimation using temperature-depth profiles in a complex environment and a changing climate.
abstract: Obtaining reliable estimates of vertical groundwater flows remains a challenge but is of critical importance to the management of groundwater resources. When large scale land clearing or groundwater extraction occurs, methods based on water table fluctuations or water chemistry are unreliable. As an alternative, a number of methods based on temperature-depth (T-z) profiles are available to provide vertical groundwater flow estimates from which recharge rates may be calculated. However, methods that invoke 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, but they typically include unrealistic or restrictive assumptions (e.g. no flow initial conditions or linear surface warming). Here, 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 groundwater catchment in South Australia. T-z profiles from seven wells (ranging from high elevation to near sea level) were utilised, in addition to mean annual air temperatures at nearby weather stations to estimate boundary conditions, and thermal properties were estimated from down borehole geophysics. Temperature based flux estimates were 5 to 23mmy-1, which are similar to those estimated using chloride mass balance. This study illustrates that T-z profiles can be studied to estimate recharge in environments where more commonly applied methods fail.
authors.affiliation: School of Earth, Atmosphere and Environment, Monash University, Clayton, Vic 3800, Australia; National Centre for Groundwater Research and Training, GPO Box 2100, Flinders University, Adelaide, SA 5001, Australia. Electronic address: dylan.irvine@monash.edu.
authors.forename: Dylan J
authors.initials: DJ
authors.lastname: Irvine
authors.affiliation: School of Geography and Earth Sciences, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada.
authors.forename: Barret L
authors.initials: BL
authors.lastname: Kurylyk
authors.affiliation: School of Earth, Atmosphere and Environment, Monash University, Clayton, Vic 3800, Australia; National Centre for Groundwater Research and Training, GPO Box 2100, Flinders University, Adelaide, SA 5001, Australia.
authors.forename: Ian
authors.initials: I
authors.lastname: Cartwright
authors.affiliation: School of the Environment, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia.
authors.forename: Mariah
authors.initials: M
authors.lastname: Bonham
authors.affiliation: School of the Environment, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia; Federal Institute for Geosciences and Natural Resources (BGR), Hannover 30655, Germany.
authors.forename: Vincent E A
authors.initials: VEA
authors.lastname: Post
authors.affiliation: School of the Environment, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia; National Centre for Groundwater Research and Training, GPO Box 2100, Flinders University, Adelaide, SA 5001, Australia.
authors.forename: Eddie W
authors.initials: EW
authors.lastname: Banks
authors.affiliation: School of the Environment, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia; National Centre for Groundwater Research and Training, GPO Box 2100, Flinders University, Adelaide, SA 5001, Australia.
authors.forename: Craig T
authors.initials: CT
authors.lastname: Simmons
keywords: Geothermics; Groundwater; Heat tracing; Land use change; Surface warming; Water resources