Heterogeneous Aquifers Research Articles

Backward Location and Travel Time Probabilities for Pollutants Moving in Three-Dimensional Aquifers: Governing Equations and Scale Effect

Backward probabilities have been used for decades to track hydrologic targets such as pollutants in water, but the convenient deviation and scale effect of backward probabilities remain unknown. This study derived backward probabilities for groundwater pollutants and evaluated their scale effect in heterogeneous aquifers. Three particle-moving methods, including the backward-in-time discrete random-walk (DRW), the backward-in-time continuous time random-walk (CTRW), and the particle mass balance, were proposed to derive the governing equation of backward location and travel time probabilities of contaminants. The resultant governing equations verified Kolmogorov’s backward equation and extended it to transient flow fields and aquifers with spatially varying porosity values. An improved backward-in-time random walk particle tracking technique was then applied to approximate the backward probabilities. Next, the scale effect of backward probabilities of contamination was analyzed quantitatively. Numerical results showed that the backward probabilities were sensitive to the vertical location and length of screened intervals in a three-dimensional heterogeneous alluvial aquifer, whereas the variation in borehole diameters did not influence the backward probabilities. The scale effect of backward probabilities was due to different flow paths reaching individual intervals under strong influences of subsurface hydrodynamics and heterogeneity distributions, even when the well screen was as short as ~2 m and surrounded by highly permeable sediments. Further analysis indicated that if the scale effect was ignored, significant errors may appear in applications of backward probabilities of groundwater contamination. This study, therefore, provides convenient methods to build backward probability models and sheds light on applications relying on backward probabilities with a scale effect.

Effects of different permeable lenses on nitrobenzene transport during air sparging remediation in heterogeneous porous media

Air sparging (AS) is considered an effective remediation technology for groundwater contaminated by volatile organic compounds. However, the effects of AS remediation of heterogeneous aquifers with lenses of different permeability are still unclear, which limits the application of AS technology. In this study, the effects of different permeable lenses on nitrobenzene (NB) transport were quantitatively analysed by tracking the temporal and spatial evolutions of the NB concentration and using light transmission visualisation technology to observe airflow. Experimental results showed that the NB outside the airflow zone of the heterogeneous aquifer containing a gravel lens was rapidly removed, which is a special phenomenon. Through moisture content monitoring and colour tracer technology, the bubble-induced water circulation zone in a gravel lens was discovered during AS. At this time, the zone of influence (ZOI) included air flow zone and water circulation zone, while previous studies believed that the ZOI only contained the air flow zone. The presence of water circulation zone in the heterogeneous aquifer with a gravel lens increased the ZOI area and average contaminant removal flux by 5 and 2.3 times, respectively, compared with those in homogeneous aquifer. These findings have modified the conventional cognition about the ZOI and are conducive to an in-depth understanding of the remediation mechanisms and a better design of AS technology in heterogeneous aquifers with different permeable lenses.

Impact of layered heterogeneity on thermal response test interpretation performed on a standing column well operated without bleed

This paper presents a comprehensive field testing programme conducted in Mirabel, Quebec, that aims to demonstrate the thermal effectiveness of a standing column well installed in a pervious layered aquifer. The first-order approximation of the infinite line source model of a thermal response test in the absence of bleed suggested that heat conduction alone could not explain the thermal response obtained at a test standing column well. To further investigate this hypothesis, a numerical model that couples the state equations for heat transfer and groundwater flow is developed and exploited to assess the contribution of advective heat transfer. A comparative study involving four cases is presented to analyse the effect of the aquifer heterogeneity in terms of hydraulic and thermal conductivity on the thermal response of test well. The results show that in contrast to the work currently available in the literature, the advective heat transfer mechanism can have a large contribution to the thermal response in specific geological environment, even without bleed. In this particular case, advection is approximately 265 times more important than conduction. This shows that layered heterogeneity and mean hydraulic conductivity can significantly impact the thermal response of a standing column well operating without bleed. The results presented in this study show that hydrogeological conditions should be given greater consideration by incorporating local hydrogeological features to replicate the experimental measurements of the thermal response test.

Experimental study of viscosity modification coupled with phase transfer catalysis for enhanced remediation of non-aqueous phase trichloroethene polluted heterogeneous aquifer

The degradation of dense non-aqueous phase liquid trichloroethene in low permeability zone is a challenging issue due to limited mass transfer between water-soluble oxidants (i.e., MnO4-) and residual phase trichloroethene and the bypassing of amendments in low permeability zone. This work accomplished trichloroethene oxidation enhancement through coupling viscosity modification by using xanthan with phase transfer of MnO4- by using phase transfer catalyst (PTC). Experiments were conducted by sand columns and 2D-tanks, and results revealed that after ~11.7 g of trichloroethene was injected in each tank, the mass of trichloroethene degradation was 1.3, 5.9, 6.9 and 8.5 g in MnO4-, MnO4- + xanthan, MnO4- + PTC and MnO4- + PTC + xanthan reaction systems, respectively. Combining PTC and xanthan with MnO4- increased the rate of continuous formation of Cl-, reflected in the acceleration of heterogeneous reactions and MnO4- transport enhancement in low permeability zone by PTC and xanthan. Moreover, PTC promoted dissolved Mn (Ⅱ) and Mn (Ⅲ) formation in the process of MnO4- reduction, and thus effectively inhibited MnO2 generation. In conclusion, the results revealed that PTC and xanthan could perform their respective contributions to mass transfer and amendment transport for jointly enhanced the remediation of trichloroethene polluted heterogeneous aquifer.

Revealing vertical aquifer heterogeneity and hydraulic anisotropy by pumping partially penetrating wells

The stratification of sedimentary aquifers introduces spatial variability in hydraulic conductivity, primarily between individual horizontal layers. On larger scales, the vertical heterogeneity enhances hydraulic anisotropy, with the horizontal conductivity typically exceeding the vertical one. In this study, the hydraulic anisotropy of a stratified aquifer is estimated from data of hydraulic tests in which water is sequentially extracted from well sections screened at different depths, and the hydraulic response is measured at various multilevel observation wells. The applicability of the method is demonstrated by field tests in a fluvial gravel aquifer in the Upper Rhine Valley, Germany. A homogeneous anisotropic model, and models with three and five anisotropic layers, are fitted to the measured drawdowns in the steady-shape regime, in which differences in hydraulic head between observation locations do not change over time even though the head values themselves change. The position of the five horizontal layers is based on the lithology of the drilling profile at the pumping-well location. The three-layer model is achieved by merging insensitive or similar layers with sensitive layers. The fits result in estimates of the radial and vertical hydraulic conductivities for all layers of the respective models, which are upscaled to effective parameters over the entire depth in the case of the multilayer models. The homogeneous model shows significantly higher errors than those of the heterogeneous models. The heterogeneous locally anisotropic models not only reveal vertical variability of hydraulic conductivity, but also lead to a three-times larger anisotropy ratio upon upscaling.

Evaluation of 1,4-dioxane attenuation processes at the Gelman Site, Michigan, USA

1,4-Dioxane released at the Gelman Site in Washtenaw County, Michigan, produced a series of contaminant plumes migrating up to 3 km through a heterogenous glacial aquifer system. An analysis of 1,4-dioxane concentrations in the Eastern Area of the Gelman Site between 2011 and 2017 documented a mass balance deficit of 2200 kg in excess of 2100 kg of 1,4-dioxane removed via remediation. Five mechanisms were evaluated to account for the mass deficiency: sorption, matrix diffusion, biodegradation, surface discharge, and bypass of the existing monitoring well network.The mass of 1,4-dioxane sorbed to aquifer and aquitard materials and the mass of 1,4-dioxane diffused into low permeability zones were estimated. However, decreasing aqueous concentrations across most of the contaminated area between 2011 and 2017 are expected to induce desorption and back diffusion during this period. Surface water discharge to a storm drain in the downgradient portion of the site was analyzed using concentration measurements and stream gage data. Results suggest that 1,4-dioxane mass entering the drain during the period between 2011 and 2017 was insufficient to account for the mass deficiency.Although available geochemical measurements indicate predominantly anaerobic aquifer conditions at the Gelman Site, biodegradation of 1,4-dioxane was estimated using first order decay rate constants from other sites where conditions may be more favorable. Results suggest that biodegradation could explain some but not all of the missing mass.Bypass of the downgradient monitoring well network is the most parsimonious explanation for the 1,4-dioxane mass deficit. This conclusion is supported by documented flow path complexity through the aquifer system and the sparse density of monitoring wells in the downgradient Eastern Area. These findings underscore the importance of characterizing aquifer heterogeneity when modeling and remediating persistent groundwater contaminants such as 1,4-dioxane.

Potential effects on groundwater quality associated with infiltrating stormwater through dry wells for aquifer recharge

Dry wells (gravity-fed infiltration wells) have frequently been used to recharge aquifers with stormwater, especially in urban areas, as well as manage flood risk and reduce surface water body contamination from stormwater pollutants. However, only limited assessment of their potential adverse impacts on groundwater quality exists. Dry well recharge can bypass significant portions of the filtering-capacity of the vadose zone. Stormwater and groundwater monitoring data and analysis of transport of a wide range of historic and current-use stormwater chemicals of concern is lacking. To address these gaps, two dry wells were constructed with vegetated and structural pretreatment features to assess the likelihood of stormwater contaminants reaching the aquifer. We monitored, assessed, and compared the presence of contaminants in stormwater to water quality in the vadose zone and shallow groundwater after it passed through the dry well. The dry wells were installed at a suburban residential and at a suburban commercial site. The selected sites were overlying a regional, unconsolidated, and highly heterogeneous alluvial aquifer system. Stormwater, vadose zone, and groundwater samples were collected during five storms and analyzed for over 200 contaminants of concern. Relatively few contaminants were detected in stormwater, generally at low concentrations. Prior to stormwater entering the dry well, 50–65% of contaminants were removed by vegetated pretreatment. In groundwater, metals such as aluminum and iron were detected at similar concentrations in both upgradient and downgradient wells, suggesting the source of these metals was not dry well effluent. Naturally occurring metals such as chromium and arsenic were not detected in stormwater but were found at elevated concentrations in groundwater. A modeling assessment suggests that the travel time of metals and hydrophobic organic contaminants to the water table at these sites ranges from years to centuries, whereas water soluble pesticides would likely reach the water table within days to months. The modeling assessment also showed that more vulnerable sites with higher fraction of alluvial sands would have much shorter contaminant travel times. However, none of the contaminants assessed reached concentrations that pose a risk to human health across the scenarios considered. No evidence was found, either through direct measurements or vadose zone modeling, that contaminants present in suburban stormwater degraded or would degrade groundwater quality at the studied sites and site conditions. Future work is needed to address emerging contaminants of concern.

Macrodispersion and Recovery of Solutes and Heat in Heterogeneous Aquifers

AbstractThe recovery efficiency of aquifer storage systems with radial flow fields are studied for heterogeneous aquifers. Macrodispersion, arising from spatially heterogeneous hydraulic conductivity, is modeled as a scale‐dependent mechanical dispersion process. Approximate solutions for the recovery efficiency as a function of local dispersion and macrodispersion parameters, the injection‐extraction rate and duration , and storage cycle count, are derived and validated against numerical simulations. If macrodispersion dominates and the macrodispersion coefficient scales linearly with distance, the recovery efficiency is independent of both . For sublinear and superlinear scalings, recovery increases and decreases respectively if increases. However, if local dispersion dominates, increasing always increases recovery. As macrodispersion becomes increasingly dominant with scale, the recovery efficiency may be a nonmonotonic function of , with a maximum. In homogeneous aquifers, nonmonotonicity does not occur for 1D and 2D radial flow, but occurs for 3D radial flow fields only as a function of , not . These methods may also be used for fitting local dispersion and macrodispersion parameters with push‐pull tests using recovery data, with advantages in scope of applicability and ease of data acquisition and interpretation, compared to existing push‐pull test methods, which fit to breakthrough curves and do not consider macrodispersion. Furthermore, characterizing macrodispersion with push‐pull tests may be advantageous over methods that use observation wells, as observation well placement may be challenging in highly heterogeneous aquifers. The results show that the macrodispersion parameters are not innate aquifer hydraulic properties, as their values vary with flow field geometry.

A robust deep learning workflow to predict multiphase flow behavior during geological [formula omitted] sequestration injection and Post-Injection periods

Simulation of multiphase flow in porous media is essential to manage the geologic CO2 sequestration (GCS) process, and physics-based simulation approaches usually take prohibitively high computational cost due to the nonlinearity of the coupled physics. This paper contributes to the development and evaluation of a deep learning workflow that accurately and efficiently predicts the temporal-spatial evolution of pressure and CO2 plumes during injection and post-injection periods of GCS operations. Based on a Fourier Neural Operator, the deep learning workflow takes input variables or features including rock properties, well operational controls and time steps, and predicts the state variables of pressure and CO2 saturation. To further improve the predictive fidelity, separate deep learning models are trained for CO2 injection and post-injection periods due to the difference in primary driving force of fluid flow and transport during these two phases. We also explore different combinations of features to predict the state variables. We use a realistic example of CO2 injection and storage in a 3D heterogeneous saline aquifer, and apply the deep learning workflow that is trained from physics-based simulation data and emulate the physics process. Through this numerical experiment, we demonstrate that using two separate deep learning models to distinguish post-injection from injection period generates the most accurate prediction of pressure, and a single deep learning model of the whole GCS process including the cumulative injection volume of CO2 as a deep learning feature, leads to the most accurate prediction of CO2 saturation. For the post-injection period, it is key to use cumulative CO2 injection volume to inform the deep learning models about the total carbon storage when predicting either pressure or saturation. The deep learning workflow not only provides high predictive fidelity across temporal and spatial scales, but also offers a speedup of 250 times compared to full physics reservoir simulation, and thus will be a significant predictive tool for engineers to manage the long-term process of GCS.

Uncertainty of heterogeneous hydrogeological models in groundwater flow and land subsidence simulations – A case study in Huwei Town, Taiwan

The distribution of hydrogeological materials in a three-dimensional heterogeneous aquifer system has a large effect on groundwater flow and land subsidence simulations. The hydrogeological information for regions between boreholes embeds a large amount of uncertainty into the hydrogeological model, and thus affects numerical assessment. Quantifying the effects of the heterogeneous system and hydrogeological model uncertainty on groundwater flow and land subsidence simulations is thus important. Here, data from 46 geological boreholes in Huwei Town, Taiwan, were adopted to investigate hydrogeological model uncertainty. The one-dimensional continuous-lag Markov chain and the geostatistical method were used to analyze the spatial characteristics of hydrogeological materials and generate realizations of the hydrogeological model based on the assessment results. Estimated hydrological conditions and hydraulic parameters were applied to mitigate uncertainty not caused by the hydrogeological model. The mean of the results of land subsidence in Monte Carlo simulations showed a more stable distribution than that of individual realizations, for which land subsidence might be far from the mean. Therefore, the mean and variance results provide a reliable assessment with uncertainty information for land subsidence simulations. The coefficient of variation (CV) was used to quantify the hydrogeological model uncertainty. The CV value of land subsidence was larger than that of the hydraulic head because the thickness of clay is not uniform whereas the flow pattern is smooth. The variance and CV distributions of the hydraulic head and land subsidence provide uncertainty information that can be used to guide site investigations. A heterogeneous hydrogeological model with uncertainty quantification should be carefully applied to land subsidence simulations to obtain reasonable results.

Impact of planned heterogeneity of hydraulic conductivity on the results of pumping in an isolated unconfined layer

The paper presents the results of numerical simulation of cluster pumping test in an heterogeneous aquifer with transmissivtyvariability described by the model of a stationary random field of its logarithm with a given scale of correlation in the plan. The case of comparable planar distance to observation wells and correlation scale is considered. Parameters of the model of transmissivity heterogeneity of the simulated aquifer are obtained from the data of experimental tests carried out within the limits of the South Voronezhskoye groundwater field. The simulation has shown that the average results of interpretation of these cluster pumping data correspond to the geometric value of the transmissivity, which confirms the previously obtained approximate theoretical result for the model of small-scale heterogeneity and extends it to an almost important case of similarity of cluster well test planar sizes and spatial scale of heterogeneity. Thus, the present study has confirmed the possibility to apply standard methods in processing of cluster pumping data under planned heterogeneity conditions to estimate the equivalent aquifer transmissivity in the well cluster location area.

Groundwater Circulation Enhanced Electrobioremediation of 1,2-Dichloroethane in a Simulated Heterogeneous Aquifer

Groundwater Circulation Enhanced Electrobioremediation of 1,2-Dichloroethane in a Simulated Heterogeneous Aquifer

Stochastic deep collocation method based on neural architecture search and transfer learning for heterogeneous porous media

We present a stochastic deep collocation method (DCM) based on neural architecture search (NAS) and transfer learning for heterogeneous porous media. We first carry out a sensitivity analysis to determine the key hyper-parameters of the network to reduce the search space and subsequently employ hyper-parameter optimization to finally obtain the parameter values. The presented NAS based DCM also saves the weights and biases of the most favorable architectures, which is then used in the fine-tuning process. We also employ transfer learning techniques to drastically reduce the computational cost. The presented DCM is then applied to the stochastic analysis of heterogeneous porous material. Therefore, a three dimensional stochastic flow model is built providing a benchmark to the simulation of groundwater flow in highly heterogeneous aquifers. The performance of the presented NAS based DCM is verified in different dimensions using the method of manufactured solutions. We show that it significantly outperforms finite difference methods in both accuracy and computational cost.

Mapping of hydraulic transmissivity field from inversion of tracer test data using convolutional neural networks. CNN-2T

This paper introduces a new concept for mapping hydraulic transmissivity from temporal concentration data collected in multiple tracer tests. Based on convolutional neural network, the principle uses an encoder-decoder architecture with multiple neural layers to establish a relationship between the concentration data and the transmissivity field. This relationship is established in two phases with two networks. The first network is designated and trained to reconstruct a transmissivity field using data from a single tracer test. To improve the reconstruction quality, the second network then performs a joint interpretation for multiple tracer tests, which reprocesses all the transmissivity resulted from the first network for each individual tracer test. Both networks are trained by synthetic data, where the transmissivity models are generated with a Gaussian variogram and its properties are considered as prior information on the aquifer heterogeneity. Tracer tests are derived numerically by solving the forward problem to obtain the corresponding concentration data that feed the training. The trained networks accurately map the transmissivity fields, of which the accuracy relies on the volume and nature of the heterogeneities of training models, as well as the number of piezometers used to monitor the concentration changes. Reconstruction quality, on the other hand, is less influenced by data noise. Effective training requires a large dataset, but the time required for dataset generation is only on the order of the Gauss-Newton algorithm in a conventional inversion, while the trained network performs inference instantly.

Characterization Method and Application of Heterogeneous Reservoir Based on Different Data Quantity

Abstract Deep saline aquifers have strong heterogeneity under natural conditions, which affects the migration of carbon dioxide (CO2) injection into the reservoir. How to characterize the heterogeneity of rock mass is of great significance to research the CO2 migration law during CO2 storage. A method is proposed to construct different heterogeneous models from the point of view of whether the amount of data is sufficient or not, the wholly heterogeneous model with sufficient data, the deterministic multifacies heterogeneous model which is simplified by lithofacies classification, and the random multifacies heterogeneous model which is derived from known formation based on transfer probability theory are established, respectively. Numerical simulation is carried out to study the migration law of CO2 injected into the above three heterogeneous models. The results show that the migration of CO2 in heterogeneous deep saline aquifers shows a significant fingering flow phenomenon and reflect the physical process in CO2 storage; the migration law of CO2 in the deterministic multifacies heterogeneous model is similar to that in the wholly heterogeneous model and indicates that the numerical simulation of simplifying the wholly heterogeneous structure to the lithofacies classification structure is suitable for simulating the CO2 storage process. The random multifacies heterogeneous model based on the transfer probability theory accords with the development law of sedimentary formation and can be used to evaluate the CO2 migration law in unknown heterogeneous formations. On the other hand, by comparing the dry-out effect of CO2 in different heterogeneous models, it is pointed out that the multifacies characterization method will weaken the influence due to the local homogenization of the model in small-scale research; it is necessary to refine the grid and subdivide the lithofacies of the local key area elements to eliminate the research error. The research results provide feasible references and suggestions for the heterogeneous modeling of the missing data area and the simplification of large-scale heterogeneous models.

Using Multiple Partially-Penetrating Wells (Mppws) to Improve the Performance of High-Temperature Ates Systems: Well Operation, Storage Conditions and Aquifer Heterogeneity

Using Multiple Partially-Penetrating Wells (Mppws) to Improve the Performance of High-Temperature Ates Systems: Well Operation, Storage Conditions and Aquifer Heterogeneity

Numerical modeling and evaluation of lab-scale CO2-injection experiments based on electrical resistivity measurements

This paper presents numerical models for validating electrical resistivity (ER)-derived carbon dioxide (CO2) saturation obtained from lab-scale CO2 flooding experiments. ER assessments have generally been implemented using Archie's empirical equation, but it is only applicable to non-saline water, homogeneous medium, and non-conductive minerals. Therefore, it is necessary to develop a reliable numerical model to scale up experimental results by calibrating uncertain properties, such as capillary pressure, relative permeability, and aquifer heterogeneity. Cylindrical sandstone samples from the homogeneous Berea sandstone and heterogeneous Tako sandstone were prepared to evaluate CO2 transport within brine-saturated media. The reliability of the numerical method was verified by the trajectories of ER-derived CO2 saturation (SCO2) in the homogeneous Berea sandstone, which showed similar profiles and a root mean square error (RMSE) of 0.0503. The aquifer heterogeneity of the Tako sandstone influenced CO2 transport, i.e., its frontal velocity, by producing retardation at the less porous layers, whereas the homogeneous Berea sandstone showed consistent movement of the CO2 front. The numerical simulation of the heterogeneous Tako sandstone confirmed the effects of the less porous layers and matched the experimental profiles of SCO2, with an RMSE of 0.0421. The developed models enable validation of ER-derived SCO2 at the early stage and forecasting of the CO2 distribution in heterogeneous saline aquifers.

An Adaptive Hybrid Vertical Equilibrium/Full‐Dimensional Model for Compositional Multiphase Flow

AbstractEfficient compositional models are required to simulate underground gas storage in porous formations where, for example, gas quality (such as purity) and loss of gas due to dissolution are of interest. We first extend the concept of vertical equilibrium (VE) to compositional flow, and derive a compositional VE model by vertical integration. Second, we present a hybrid model that couples the efficient compositional VE model to a compositional full‐dimensional model. Subdomains, where the compositional VE model is valid, are identified during simulation based on a VE criterion that compares the vertical profiles of relative permeability at equilibrium to the ones simulated by the full‐dimensional model. We demonstrate the applicability of the hybrid model by simulating hydrogen storage in a radially symmetric, heterogeneous porous aquifer. The hybrid model shows excellent adaptivity over space and time for different permeability values in the heterogeneous region, and compares well to the full‐dimensional model while being computationally efficient, resulting in a runtime of roughly one‐third of the full‐dimensional model. Based on the results, we assume that for larger simulation scales, the efficiency of this new model will increase even more.

Estimation of groundwater flow along complex coastal aquifers in presence of tidal waves

ABSTRACT Coastal aquifers are of interest for many years in understanding the transient interaction of tides and groundwater. With existing studies, water table fluctuations in the two zonal aquifers of various configurations separated by horizontal or sloping bases have been addressed; however, flow properties in respective aquifers are not addressed. The present study is an application of the previous study and it addresses flow properties such as flow rate at both ends of the complex coastal aquifer, and volumetric exchanges of groundwater at the proximity surface and at the boundary point. The combined effect of the bed slope and tidal waves on groundwater flow properties is addressed by obtaining the analytical expressions. Furthermore, numerical simulation using a finite difference method (FDM) is carried out for the flow rate and analytical solution is compared with it and found to be satisfactory. The hydrographs representing the flow rate and amount of groundwater exchanged are studied with different bed slopes and for various time lags. The flow analysis is carried out in a heterogeneous aquifer by changing various hydrological parameters. The study focused on dependency of groundwater hydraulic properties for the sloping zone on the horizontal zone. Based on the results, the groundwater flow in the complex aquifer systems is discussed.

How groundwater time series and aquifer property data explain heterogeneity in the Permo-Triassic sandstone aquifers of the Eden Valley, Cumbria, UK

A novel investigation of the impact of meteorological and geological heterogeneity within the Permo-Triassic Sandstone aquifers of the River Eden catchment, Cumbria (UK), is described. Quantifying the impact of heterogeneity on the water cycle is increasingly important to sustainably manage water resources and minimise flood risk. Traditional investigations on heterogeneity at the catchment scale require a considerable amount of data, and this has led to the analysis of available time series to interpret the impact of heterogeneity. The current research integrated groundwater-level and meteorological time series in conjunction with aquifer property data at 11 borehole locations to quantify the impact of heterogeneity and inform the hydrogeological conceptual understanding. The study visually categorised and used seasonal trend decomposition by LOESS (STL) on 11 groundwater and meteorological time series. Decomposition components of the different time series were compared using variance ratios. Though the Eden catchment exhibits highly heterogeneous rainfall distribution, comparative analysis at borehole locations showed that (1) meteorological drivers at borehole locations are broadly homogeneous and (2) the meteorological drivers are not sufficient to generate the variation observed in the groundwater-level time series. Three distinct hydrogeological regimes were identified and shown to coincide with heterogeneous features in the southern Brockram facies, which is the northern silicified region of the Penrith Sandstone and the St Bees Sandstone. The use of STL analysis in combination with detailed aquifer property data is a low-impact insightful investigative tool that helps guide the development of hydrogeological conceptual models.