Search

This study introduces a new analytical framework that employs the image‐well method to simulate the spatial and temporal temperature distribution in vertical borehole thermal energy storage (BTES) systems. The model accommodates complex boundary shapes and conditions, including insulation, convection, and constant temperature, without requiring iterative solutions at each time step. The model's accuracy and utility are demonstrated through an application to a borehole heat exchanger cluster arranged in an octagonal shape with insulating boundaries, based on a BTES site in Drake Landing (Canada). Model predictions are validated against a finite element model, showing a root‐mean‐square error of 0.012°C. A global sensitivity analysis highlights the influence of thermal parameters on system performance, identifying the heat flux of the borehole heat exchanger as the most sensitive parameter. Overall, this approach combines the advantages of analytical and numerical techniques to provide a clear and efficient tool for evaluating BTES systems, offering significant potential for advancing sustainable energy solutions. [ABSTRACT FROM AUTHOR]

Locating clandestine graves presents significant challenges to law enforcement agencies, necessitating the testing of grave detection techniques. This experimental study, conducted under Australian field conditions, assesses the effectiveness of time-lapse ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) in detecting pig burials as simulated forensic cases. The research addresses two key questions: (1) observability of graves using GPR and ERT, and (2) changes in geophysical responses with reference to changing climatic conditions. The principal novelty of this research is its Australian focus—this is the first time-lapse GPR and ERT study used to locate clandestine graves in Australia. The results reveal that both GPR and ERT can detect graves; however, ERT demonstrates greater suitability in homogeneous soil and anomalously wet climate conditions, with the detectability affected by grave depth. This project also found that resistivity values are likely influenced by soil moisture and decomposition fluids; however, these parameters were not directly measured in this study. Contrastingly, although GPR successfully achieved 2 m penetration in each survey, the site's undeveloped soil likely resulted in inconsistent detectability. The findings underscore the significance of site-specific factors when employing GPR and/or ERT for grave detection, including soil homogeneity, climate conditions, water percolation, and body decomposition state. These findings offer practical insights into each technique's utility as a search tool for missing persons, aiding law enforcement agencies with homicide cases involving covert graves. [ABSTRACT FROM AUTHOR]

The sustainability of limited freshwater resources in coastal settings requires an understanding of the processes that affect them. This is especially relevant for freshwater lenses of oceanic islands. Yet, these processes are often obscured by dynamic oceanic water levels that change over a range of timescales. We use regression deconvolution to estimate an oceanic response function (ORF) that accounts for how sea-level fluctuations affect measured groundwater levels, thus providing a clearer understanding of recharge and withdrawal processes. The method is demonstrated using sea-level and groundwater-level measurements on the island of Norderney in the North Sea (northwestern Germany). We expect that the method is suitable for any coastal groundwater system where it is important to understand processes that affect freshwater lenses or other coastal freshwater resources. [ABSTRACT FROM AUTHOR]

Estimating groundwater recharge rates is important to understand and manage groundwater. Numerous studies have used collated recharge datasets to understand and project regional or global-scale recharge rates. Recharge estimation methods each have distinct assumptions, quantify different recharge components, and operate over different temporal scales. To address these challenges, we use over 200,000 groundwater chloride measurements to estimate groundwater recharge rates using the chloride mass balance (CMB) method across Australia. Recharge rates were produced stochastically using gridded chloride deposition, runoff, and precipitation datasets. After filtering out recharge rates where the assumptions of the method may have been compromised, 98,568 estimates of recharge were produced. The resulting recharge rates and 17 spatial datasets were integrated into a random forest regression algorithm, generating a high-resolution (0.05°) model of recharge rates across Australia. The regression reveals that climate-related variables, including precipitation, rainfall seasonality, and potential evapotranspiration, exert the most significant influence on recharge rates, with vegetation (NDVI) also contributing significantly. Importantly, both the mean values of the recharge point dataset (43.5 mm y-1) and of the spatial recharge model (22.7 mm y-1) are notably lower than those reported in previous studies, underscoring the prolonged timescale of the CMB method and the potential disparities arising from distinct recharge estimation methodologies. This study presents a robust and automated approach to estimate recharge using the CMB method, offering a unified model based on a single estimation method. The resulting datasets, the Python script for recharge rate calculation, and the spatial recharge models collectively provide valuable insights for water resources management across the Australian continent and similar approaches can be applied globally. [ABSTRACT FROM AUTHOR]

In recent years, there has been a growing interest in utilizing the groundwater response to Earth tides as a means to estimate subsurface properties. However, existing analytical models have been insufficient in accurately capturing realistic physical conditions. This study presents a new analytical solution to calculate groundwater response to Earth tide strains, including storage and compressibility of the aquitard, borehole storage and skin effects. We investigate the effects of aquifer and aquitard parameters on well water response to Earth tides at two dominant frequencies (O1 and M2) and compare our results with hydraulic parameters obtained from a pumping test. Inversion of the six hydro-geomechanical parameters from amplitude response and phase shift of both semi-diurnal and diurnal tides provides relevant information about aquifer transmissivity, storativity, well skin effect, aquitard hydraulic conductivity and diffusivity. The new model is able to reproduce previously unexplained observations of the amplitude and frequency responses. We emphasize the usefulness in developing relevant methodology to use the groundwater response to natural drivers for characterizing hydrogeological systems. [ABSTRACT FROM AUTHOR]

Subsurface hydraulic and geomechanical properties can be estimated from well water level responses to Earth and atmospheric tides. However, the limited availability of analytical solutions restricts the applicability of this approach to realistic field conditions. We present a new and rigorous analytical solution for modelling flow between a subsurface-well system caused by harmonic atmospheric loading. We integrate this into a comprehensive workflow that also estimates subsurface properties using a well-established Earth tide method. When applied to groundwater monitoring datasets obtained from two boreholes screened in a sand aquifer in the Mary-Wildman Rivers region (Northern Territory, Australia), estimated hydraulic conductivity and specific storage agree. Results also indicate that small vertical leakage occurs in the vicinity of both boreholes. Furthermore, the estimated geomechanical properties were within the values reported in literature for similar lithological settings. Our new solution extends the capabilities of existing approaches, and our results demonstrate that analysing the groundwater response to natural tidal forces is a low-cost and readily available solution for unconsolidated, hydraulically confined, and undrained subsurface conditions. This approach can support well-established characterisation methods, increasing the amount of subsurface information. [ABSTRACT FROM AUTHOR]

When analyzing convective heat transport, local thermal equilibrium (LTE) between the solid and fluid phases of water-saturated porous media is commonly assumed. However, experiments investigating the scope of validity of this assumption are lacking. We conducted heat transport experiments using two types of porous media having the same grain size (5 mm) but contrasting thermal properties (glass and polyoxymethylene) for different thermal Péclet numbers between 1.1 and 19.8. We used specifically crafted sensors to separately measure the temperature of the solid and fluid phases. Both LTE and local thermal non-equilibrium (LTNE) models were used to analyze the measurement data. While the LTE model was appropriate for all experimental conditions, small signatures of LTNE were detected. The experimental data and the sensitivity analysis using the LTNE model demonstrated that the volumetric heat capacity of solid plays a more significant role in causing LTNE than the solid thermal conductivity. [ABSTRACT FROM AUTHOR]

The sustainability of limited freshwater resources in coastal settings requires an understanding of the processes that affect them. This is especially relevant for freshwater lenses of oceanic islands. Yet, these processes are often obscured by dynamic oceanic water levels that change over a range of time scales. We use regression deconvolution to estimate an Oceanic Response Function (ORF) that accounts for how sea-level fluctuations affect measured groundwater levels, thus providing a clearer understanding of recharge and withdrawal processes. The method is demonstrated using sea-level and groundwaterlevel measurements on the island of Norderney in the North Sea (Northwest Germany). We expect that the method is suitable for any coastal groundwater system where it is important to understand processes that affect freshwater lenses or other coastal freshwater resources. [ABSTRACT FROM AUTHOR]