Conduit Flow Research Articles

Dissolving the mystery of subsurface controls on snowmelt–discharge dynamics in karst mountain watersheds using hydrologic timeseries

AbstractStreamflow generation in mountain watersheds is strongly influenced by snow accumulation and melt as well as groundwater connectivity. In mountainous regions with limestone and dolomite geology, bedrock formations can host karst aquifers, which play a significant role in snowmelt–discharge dynamics. However, mapping complex karst features and the resulting surface‐groundwater exchanges at large scales remains infeasible. In this study, timeseries analysis of continuous discharge and specific conductance measurements were combined with gridded snowmelt predictions to characterize seasonal streamflow response and evaluate dominant watershed controls across 12 monitoring sites in a karstified 554 km2 watershed in northern Utah, USA. Immense surface water hydrologic variability across subcatchments, years and seasons was linked to geologic controls on groundwater dynamics. Unlike many mountain watersheds, the variability between subcatchments could not be well described by typical watershed properties, including elevation or surficial geology. To fill this gap, a conceptual framework was proposed to characterize subsurface controls on snowmelt–discharge dynamics in karst mountain watersheds in terms of conduit flow direction, aquifer storage capacity and connectivity. This framework requires only readily measured surface water and climatic data from nested monitoring sites and was applied to the study watershed to demonstrate its applicability for evaluating dominant controls and climate sensitivity.

Unveiling the role of Atomic-Level “Pump-Driven” effect in MoS2/MnO2 for facilitating directional charge transfer in hybrid capacitive deionization

In addressing the limitations imposed by the inherently low electronic conductivity and substantial ion transfer resistance of transition metal oxides (TMOs) in hybrid capacitive deionization (HCDI) applications, this study delineates a pioneering approach through the fabrication of a MoS2/MnO2 heterostructure, leveraging manganese dioxide (MnO2) as a model system. The investigation underscores the essentiality of constructing high-quality interfaces to act as conduits for directional charge flow, a critical but formidable challenge for enhancing desalination efficacy in electrode materials. By harnessing an atomistic “pump-driven” mechanism, the MoS2/MnO2 heterostructure demonstrably facilitates the promotion of desalination processes, underscored by the establishment of a potent local electric field (IEF) aimed at commanding charge dynamics. Empirical and computational analyses coalesce to unveil the preferential electron transfer from MoS2 to MnO2, a phenomenon precipitated by charge redistribution. This orchestrated charge flow not only augments electronic and ionic transfer efficiencies but also emboldens the MoS2/MnO2 heterostructure with enhanced desalination capabilities. The results show that MoS2/MnO2 demonstrates superior HCDI performance compared to MnO2 in a 500 mg L-1 NaCl solution at 1.2 V, with SRC of 33.21 mg g-1 and SRR of 1.50 mg g-1 min-1. The elucidation of this charge-guided dynamic, achieved through meticulous manipulation of the electronic microstructure and the IEF at the atomic scale, presents a novel paradigm for material science. This research presents an innovative approach for realizing robust charge-guided dynamics through the deliberate manipulation of the electronic microstructure and IEF of materials, employing an atomic-level “pump-driven” effect. This strategy opens new avenues for extending these principles to a broad array of advanced materials.

Discontinuous Galerkin method for the coupled dual-porosity-Brinkman model

In this paper we use the weighted discontinuous Galerkin finite element method to solve the dual-porosity-Brinkman coupling model. The dual-porosity model describes fluid flow in a dual-porosity medium composed of matrix and microfractures, while the Brinkman equation describes fluid flow in hydraulic fractures or conduits containing “debris filling” or “proppant filling”. The two models are coupled by the four physically effective interface conditions, which are constructed based on the fundamental properties of the dual-porosity model and the Brinkman-Darcy model. We provide a weighted discontinuous discrete scheme for the model and derive the optimal error estimates. Through numerical experiments, we verify the properties of the model and the advantages of the numerical method, such as the optimal convergence rate of the numerical solution and the simulation of the flow characteristics around hydraulic fractures and conduits.

Impact of 4D-Flow CMR Parameters on Functional Evaluation of Fontan Circulation.

We sought to evaluate the potential clinical role of 4D-flow cardiac magnetic resonance (CMR)-derived energetics and flow parameters in a cohort of patients' post-Fontan palliation. In patients with Fontan circulation who underwent 4D-Flow CMR, streamlines distribution was evaluated, as well a 4D-flow CMR-derived energetics parameters as kinetic energy (KE) and energy loss (EL) normalized by volume. EL/KE index as a marker of flow efficiency was also calculated. Cardiopulmonary exercise test (CPET) was also performed in a subgroup of patients. The population study included 55 patients (mean age 22±11 years). The analysis of the streamlines revealed a preferential distribution of the right superior vena cava flow for the right pulmonary artery (62.5±35.4%) and a mild preferential flow for the left pulmonary artery (52.3±40.6%) of the inferior vena cave-pulmonary arteries (IVC-PA) conduit. Patients with heart failure (HF) presented lower IVC/PA-conduit flow (0.75±0.5 vs 1.3±0.5 l/min/m2, p=0.004) and a higher mean flow-jet angle of the IVC-PA conduit (39.2±22.8 vs 15.2±8.9, p<0.001) than the remaining patients. EL/KE index correlates inversely with VO2/kg/min: R: -0.45, p=0.01 peak, minute ventilation (VE) R: -0.466, p<0.01, maximal voluntary ventilation: R:0.44, p=0.001 and positively with the physiological dead space to the tidal volume ratio (VD/VT) peak: R: 0.58, p<0.01. From our data, lower blood flow in IVC/PA conduit and eccentric flow was associated with HF whereas higher EL/KE index was associated with reduced functional capacity and impaired lung function. Larger studies are needed to confirm our results and to further improve the prognostic role of the 4D-Flow CMR in this challenging population.

Depositional facies controls on reservoir rock typing and heterogeneity: Devonian siliciclastic succession, south central Ghadames basin, Libya

The Devonian sedimentary succession hosts the most potential reservoir targets in Ghadames Basin, Northwest Libya. This succession consists of a complex pattern of siliciclastic facies deposited during successive episodes of sea level fall and rise, thereby leading to a large scale heterogeneity in sandstone facies connectivity and distribution. The present study integrates core sedimentology, wireline logs, and routine and special core analysis to establish a framework for predicting the distribution of the best Devonian reservoir rock types (RRTs). A lowstand amalgamated fluvial sandstone bars only exist in the Lower Devonian Tadrart Formation; the other Devonian rock units consist of transgressive and highstand tidally-influenced estuarine and deltaic facies. The pore system characteristics are controlled by initial depositional attributes where open, megapores with entry displacement pressures <10 psi occur in the quartzose, high energy fluvial sandstone bars, delta distributary channels and mouth bars. These facies are classified as RRTI and are mostly associated with lowstand and late highstand facies. In contrast, the other RRTs display tight pore system with elevated irreducible water content >20%. RRTI rocks account for greater than 90% of the fluid flow capacity in the Devonian reservoirs. A link between the facies depositional setting, RRT distribution, vertical amalgamation and lateral compartmentalization of flow conduits, barriers and baffles zones has been proposed, thereby promoting the predictability of the best reservoir targets.

Vulcanian eruptions at Sakurajima Volcano: geophysical data, numerical modelling, and petrological evidence

We investigated the magma conduit system beneath three active craters that have repeatedly generated Vulcanian eruptions at Sakurajima Volcano, Japan, by analysing seismic, infrasound, and tilt data. The hypocentres of the earthquakes associated with the Vulcanian eruptions are distributed separately at shallow depths of approximately 0.5 km beneath the craters. Infrasound indicated that the swelling of the crater floor starts approximately 0.2 s after the occurrence of earthquakes and that the eruption starts about 0.3 to 0.5 s later. During an eruption, tilt vectors at a station approximately 2.7 km far from the active craters indicated a deflationary trend directed toward one of the three active craters. A 1-D conduit flow simulation indicated pressure build-up at a depth of 0.4–1.0 km beneath the crater, consistent with previously reported pressure sources during eruptions detected by geodesy. Volcanic lapilli emitted from the three craters have the same chemical composition; hence, Vulcanian eruptions of all three studied craters originate from a common magma source.

Advancing sanitary surveillance: Innovating a live-feed sewer monitoring framework for effective water level and chamber cover detections

Efficient sanitation system management relies on vigilant sewage surveillance to uphold environmental hygiene. The absence of robust monitoring infrastructure jeopardizes unimpeded conduit flow, leading to floods and contamination. The accumulation of harmful gases in sewer chambers, coupled with tampered lids, compounds sewer network challenges, resulting in structural damage, disruptions, and safety risks from accidents and gas inhalation. Notably, even vehicular transit is vulnerable, facing collisions due to inadequately secured manholes. The core objective of this research was to deconstruct and synthesize a prototype blueprint for a live-feed sewer monitoring framework (LSMF). This involves creating a data gathering nexus (DGN) and empirically assessing diverse wireless sensing implements (WSI) for precision. Simultaneously, a geographic information matrix (GIM) was developed with algorithms to detect sewer surges, blockages, and missing manhole covers. Three scrutinized sensors—the LiDar TF-Luna, laser TOF400 VL53L1X, and ultrasonic JSN-SR04T—were evaluated for their ability to measure water levels in sewer vaults. The results showed that the TF-Luna LiDar sensor performed favorably within the 1.0–5.0 m range, with a standard deviation of 0.44–1.15. The TOF400 laser sensor ranked second, with a more variable standard deviation of up to 104 as obstacle distance increased. In contrast, the JSN-SR04T ultrasonic sensor exhibited lower standard deviation but lacked consistency, maintaining readings of 0.22–0.23 m within the 2.0–5.0 m span. The insights from this study provide valuable guidance for sustainable solutions to sewer surveillance challenges. Moreover, employing a logarithmic function, TF-Luna Benewake exhibited reliability at approximately 84.5%, while TOF400 VL53L1X adopted an exponential equation, boasting reliability approaching approximately 89.6%. With this navigational tool, TF-Luna Benewake maintained accuracy within ±10 cm for distances ranging from 8 to 10 m, showcasing its exceptional performance.

Influence of karst conduit’s geometry and morphology on 3D flow and transport processes: Insights from 3D tracer tests and numerical modelling

In karst, the characterization of subsurface solute and contaminant transport is a major issue that has been widely investigated due to the high vulnerability of these hydrosystems. In former studies, several researchers addressed these needs with different approaches such as laboratory experiments, field experiments, or groundwater flow and transport simulations. The objective of such approaches is to improve knowledge of transport processes in karst hydrosystems, and propose solutions to limit the downstream hydrogeological risks (contamination of water resources). In this study, we performed the 3D mapping of the karst conduit, which outlet is the Lez spring (southern France) to get the precise geometry and morphology of this fully water-filled karst conduit. Then we injected a dye in the water-filled karst conduit and performed a continuous monitoring of dye tracer recovery at three different cross-sections located downstream the injection spot, at a distance of 40 m, 90 m and 160 m, respectively. In each cross-section, five submersible fluorometer probes were positioned at different locations (top, right, down, left and central parts) along the cross-section of the karst conduit. Experimental data allowed to reconstruct the transient spatial distribution of concentration for each cross-section, which allowed assessing the propagation and evolution of solute plume over time. Monitored data also provided information about dye mixing along the karst conduit and were used to investigate the effect of karst conduit geometry, flow turbulences and velocity profiles on the mixing processes and propagation of solute plume along the conduit with numerical models. Modelling results showed that the consideration of 3D mapped karst conduit geometry and morphology allows a much better reproduction of observed transport processes and breakthrough curves, than the one obtain when considering simplified conduit geometry and morphology.

A New Index to Assess the Effect of Climate Change on Karst Spring Flow Rate

Karstic aquifers, because of their conduit system, are susceptible to climate change. Ten karst springs in the Zagros region were selected to investigate the impact of climate change under three CMIP6 scenarios: SSP1-1.9, SSP2-4.5, and SSP5-8.5. This study was conducted in three steps: downscaling climate projection, analyzing spring discharge time series, and introducing a new index to assess the impact of climate change on spring flow rate. Applying LARS-WG6, precipitation was downscaled at 14 stations in the study area. Moreover, time series and trend analysis showed that the selected springs have experienced a decrease in their flow rate. Assuming the covariance function between precipitation and spring discharge is constant, new indices (i.e., IQd, IdQd, and Icc) were introduced to highlight the effect of climate change according to the three scenarios. dQd is the variability of spring discharge from past to future, IdQd is spring discharge variability over the historical data, and Icc is the effect of precipitation and spring discharge change together. Icc has a range from −0.25 to 0.25 below and above, which is indicative that two extreme conditions including the spring dryness and overflow are in effect, respectively. The main results revealed that the degree of impact at each spring is a function of climate change scenarios and hydrogeological characteristics of the karstic systems. A more noticeable negative trend in spring flow rate is observed for the karst springs characterized by a dominant conduit flow regime and low matrix storage, located in the areas with low cumulative rainfall, and has a stronger relationship with precipitation. Based on the results, decisions on the management of karst water resources should be made considering where the springs bear free surface and pressurized flow conditions.

Evaluating physical controls on conduit flow contribution to spring discharge

The physical controls on the contribution of conduit to spring discharge, quantified as the ratio of conduit flow to spring discharge (Qc/Q), are evaluated through numerical simulations using MODFLOW-Conduit Flow Process. The controlling factors include the ratio of conduit surface roughness to conduit diameter (ε/D), the hydraulic conductivity ratio between the conduit wall and the porous matrix (Kc/K), the ratio of groundwater recharge to the hydraulic conductivity of the porous matrix, and conduit density (Cd) defined as the ratio of total conduit length to springshed area. For a single conduit, Qc/Q increases with Kc/K when flow in the conduit is laminar. When flow is turbulent, Qc/Q is stable and then decreases with ε/D, increases with Kc/K, and decreases with R/K due to the limited exchange capacity between matrix and conduit (i.e., small Kc/K). The results of hypothetical conduit networks show that Qc/Q increases with Cd but is not sensitive to the two sets of network structure evaluated. The sensitivity analysis for the Silver Springs in Florida shows that the spatial heterogeneity of conduit diameter causes higher Qc/Q, and Qc/Q is most sensitive to the conduit density, followed by R/K, and then Kc/K.

A Stokes–Darcy–Darcy model and its discontinuous Galerkin method on polytopic grids

In this paper, we propose and numerically solve a model considering confined flow in fractured porous media coupled with free flow in conduits. Such a situation arises, for example, for fluid flows in fractured vuggy carbonate reservoirs and caves/conduits, where a matrix and fractures are the main spaces for fluid storage and flow. The flow in caves and conduits is governed by the Stokes equation; the flow in fractured porous media, which consists of both a matrix and fractures, is described by a coupled Darcy–Darcy (bulk–fracture) model. Then, the two models are coupled through suitable (physically consistent) interface conditions on the interface between fractured porous media and caves/conduits, playing a key role in a physically faithful simulation that achieves high accuracy. The construction of all the interface conditions of the coupled model is based on the fundamental properties of the traditional bulk–fracture model and the well-known Stokes–Darcy model. The weak formulation is derived for the proposed model, and the well-posedness of the model is theoretically analyzed. We also propose a polyhedral discontinuous Galerkin finite element approximation for the Stokes flow in conduits and Darcy flow in the porous matrix, which is coupled with a conforming finite element scheme for the flow in the fracture. Optimal error estimates in a suitable energy norm are obtained. Two-dimensional numerical experiments are conducted to validate the proposed model and to demonstrate the features of both the model and the numerical method, such as the optimal convergence rate of the numerical solution; the detail flow characteristics around fractures, the matrix, and conduits; and the applicability to real-world problems.

Two-dimensional high-resolution numerical investigation of eddy effect in artificial rough conduits with different shapes

Subsurface conduit flow is a critical element of investigating groundwater movement in karst regions, and it is still poorly understood due to complexity of subsurface conduit geometries and the nonlinearity of the conduit flux-hydraulic gradient relationship. A significant nature of the flow nonlinearity is the occurrence of different eddies in conduits. To reveal the nonlinear nature of conduit flow, this study investigates the influence of the eddy effect on the hydraulic gradient of different rough conduits based on extensive high-fidelity numerical simulations. Overall, the hydraulic gradients of all types of rough conduits show quadratic relations with an increase in the specific discharge. In addition, the triangular rough conduit has the largest hydraulic gradient, which gradually decreases as the shape coefficient (which is used to quantify rough elements) increases. We have identified the development and evolution of eddies in different types of rough conduits in detail. This study shows that a larger specific discharge leads to a larger eddy area, and the hydraulic gradient changes exponentially with the eddy area ratio within a limited range. Finally, the relationships among specific discharges, eddy area ratio, and hydraulic gradients are constructed and summarized. The results of this investigation are helpful for developing realistic karst groundwater flow and transport models in which subsurface conduit plays a dominant role for conducting groundwater flux and mass transport.

Integrated seismic-stratigraphic, sedimentological and petrophysical approaches for characterizing the reservoir potential of early Cretaceous Alam El Bueib formation in the Meleiha concession of North Western Desert, Egypt

The Early Cretaceous late syn-rift sediments of Alam El Bueib Formation host potential, however poorly-explored reservoir targets in the north Western Desert of Egypt. The controls on depositional evolution and architecture of Alam El Bueib sedimentary facies, as well as the influence of depositional attributes on reservoir facies heterogeneity, are poorly constrained. Therefore, this study integrates seismic, sedimentological, and petrophysical data from Meleiha concession in the north Western Desert to build evolutionary models for Alam El Bueib succession and predict the architecture of the potential reservoir facies. Several channel systems were observed with a notable upward transition from complex-filled to flat-filled channels. The complex-filled channels correspond to the early highstand tidally-influenced estuarine, deltaic/estuarine sediments of Alam El Bueib-IV and Alam El Bueib-IIIG units. Matruh canyon and Alam El Bueib-IIIG fluvial sand bars were developed during a phase of forced regression, and the canyon was infilled by hemiplegic mudstones during the Late Valanginian sea level rise. The late highstand and lowstand facies of Alam El Bueib-IIIG unit present the main fluid flow conduits. The minimal degree of reservoir heterogeneity occurs in the lowstand amalgamated fluvial sandstone bars, whereas lateral and vertical reservoir heterogeneity increases in the deltaic/estuarine and estuarine successions of Alam El Bueib-IIIG and Alam El Bueib-IV, respectively. The lateral compartmentalization of the Alam El Bueib-IIIG fluvial facies against Alam El Bueib Matruh canyon shales produced excellent stratigraphic traps that should be tracked throughout the entire north Western Desert.

Shale barrier performance in petroleum systems: implications for CO 2 storage and nuclear waste disposal

Shale is often required to act as a natural barrier to fluid flow around nuclear waste repositories and above CO 2 storage sites. The small pore size of the shale matrix makes it an effective barrier to fluid flow. However, leakage could occur along faults or fractures. Experiments provide insight into fault/fracture-related leakage on short timescales (i.e. 1–10 years) compared to that needed for safe disposal (up to 1 Ma). Data collected by the petroleum industry provides strong evidence on how faults and fractures in shale impact fluid flow on such timescales. Faulted shales act as seals to petroleum reservoirs and abnormal pressures on geological timescales (&gt;10 Ma). This observation suggests that faults in shale can either form without acting as flow conduits or act as temporary conduits but then reseal. Index properties such as clay content and elastic moduli are useful for identifying shales in which faults/fractures are likely to self-seal. However, fault and fracture-related fluid flow can occur through weak shales if high overpressures are maintained. Nuclear waste repositories can be sited away from where overpressures could develop. Leakage from CO 2 storage sites is more risky because the CO 2 provides drive to maintain high pressures, which could suppress self-sealing. Thematic collection: This article is part of the Fault and top seals 2022 collection available at: https://www.lyellcollection.org/topic/collections/fault-and-top-seals-2022

Hydrochemical and hydrodynamic study to explore the origin of water in a volcanic aquifer

Abstract The current research aimed to determine the origin of ions and the type of flow system in groundwater flowing out through two types of atmospheric and hydrothermal springs by hydrochemical and hydrodynamic approaches in a volcanic aquifer. Findings revealed that the major ion types in atmospheric waters are calcic and magnesium bicarbonate, whereas hydrothermal springs predominantly indicated chloride–sodic composition, showing an evolving pattern resulting from hydrothermal and atmospheric waters mixing. Investigating the ionic ratios and the saturation index to determine the origin of ions suggests that the presence of ions in the waters can be attributed to the weathering of silicates and plagioclase-bearing minerals in the volcanic units, and in some cases, ionic exchange also plays a role. The recession curve analysis revealed a predominant conduit flow with α = 0.144 in the system feeding the representative hydrothermal spring. Two micro-regimes with α1 = 0 = 0.46 and α2 = 2.68 were detected on the hydrograph of the atmospheric representative spring, indicating the development of systems with two types of flow regimes. Estimating the Qmax/Qmin ratio for selected hydrothermal and atmospheric springs as 2.3 and 36.8, respectively, and calculating the electrical conductivity coefficient as 11% and 18% respectively, confirmed the recession curve analysis result.

Evaluation of geological structures and geothermal resources in the North Tanzania Volcanic area using remote sensing and gravity data analysis

Problems Statement and Purpose. Northern Tanzania Volcanic terrain has been a subject of evaluation for geothermal potential in the last four decades. The region is characterized by Neogene to Recent volcanic and tectonic activities. This preliminary study based on remote sensing, water chemistry, gravity data, geological structures and volcanic centers distribution reports the geothermal manifestations identified and discusses the implications on geothermal fluid pathways. Oxygen-hydrogen isotope data from water samples indicate that there were involved in the hydrothermal system. Tectono-Volcanic Structures. The Northern Tanzania Divergence (NTD) area characterized by Neogene to Recent volcanic and tectonic activities. Recent volcanic and tectonic activities are ash cone and lava dome eruption at the floor of Meru crater a century ago, dyke intrusion and volcanic eruption south of Gelai volcano, and Oldoinyo-Lengai volcano, respectively. Fumarolic activities and hot springs are dominant in a relatively young volcanic area to the north-eastern and northern part of the NTD. Data and Methods. Shuttle Radar Topography Mission (SRTM), Landsat 8 Operational Land Imager (OLI) image, water isotope analysis and gravity data were used to extract and analyze the surface and subsurface geological lineaments and map the hydrothermal alteration zones in the study area. The hydrothermal alteration is used to evaluate and identify the permeable structures. Analysis and interpretation of the length and trends of extracted lineaments were used to investigate the tectonic evolution. Geological map of a study area was digitized from the existing geological maps and the age of rocks to delineate volcanic activity and associated lineaments based on the age of the lithological domain. Digital image processing was applied to enhance the visual interpretation. Gravity data were used to give insight into the subsurface structure in the study area. Results and Discussion. The higher δ 18O values and large deviation from meteoric water lines suggest that is due to the interaction of fluids with host rocks at elevated temperatures. These are consistent with open structures that act as conduits for fluid flow. The potential field gravity data reveal a basin-like structure trending in the NNW direction. The gravity data show that the basement units gradually deepen towards the central part and that it is controlled by two main fault systems that trend N-S and NW-SE respectively. The gravity data presented here provides new constraints on the tectonic evolution and geothermal resources of the study area.

Influence of sediments burying the discharge area of a karst aquifer on the groundwater flow field—Numerical testing of conceptual models

AbstractKarst springs are a natural result of karst water discharging to the surface through unimpeded pathways where the water table meets the surface. This study investigates the impact of alluvial deposits of varying thicknesses and permeabilities burying the main outlet (karst spring) of a well‐developed conduit network on karst drainage, including the development of hydraulic heads, drainage patterns and conduit‐matrix interactions in response to a positive base‐level shift. Numerical testing using FEFLOW on a simplified conceptual model of a hypothetical karst aquifer with six different model configurations was used to examine various drainage structures (with and without flow through a conduit), spring conditions (free vs. partially/fully clogged), sediment cover thickness (20 and 50 m), and hydraulic conductivity of the sediments (low and high). The numerical testing model incorporated one‐dimensional discrete feature elements to simulate conduit flow and coupled conduit‐matrix interactions. Results indicate that even with a fully plugged outlet, the conduit network remains a significant contributor to the drainage system, collecting water from the matrix in the recharge zone. As the outlet becomes buried, the hydraulic head increases along the conduit, forcing water back up into the matrix. The elevated hydraulic head in the karst system will cause new conduits to form at the contact between limestone and sediments, creating new potential spring sites (or reactivating existing paleo‐phreatic levels). Artesian conditions will occur below the low permeability sediments. These findings provide valuable insights into the responses of natural karst systems.

Geological Structure Model for Recharge Area in Patuha Geothermal Field

Geothermal sustainability requires geological structure analysis using gravity methods for groundwater management. Geological structure analysis reviews fault data. Geological structure as a pathway for fluid movement for groundwater management in the research area, especially the Patuha Geothermal Field, West Java. This study uses global gravity model, terrestrial gravity, DEM, and geological data. The gravity method applied in this research involves calculations for latitude correction, free air correction, bouguer correction and terrain correction. The final results of this research are free air anomaly, complete Bouguer anomaly, and model evaluation (MRSE, MRE, and MAE). Free air anomaly results from free air correction of global gravity model data. DEM topography analyzes free air anomaly. The FAA data model evaluated RMSE at 1.27, MRE at 0.004, and MAE at 0.83. 138.02–280.26 mgal is the FAA range. The research area’s elevation range is 836–2431 m. Topography and free air anomaly correlate 0.75. Positive high connection. Mountains and plateaus may have positive gravity anomalies. Free air, bouguer, terrain, and CBA are applied to global gravity model data. The CBA model evaluation indicates quality. RMSE is 1.47, MRE is 0.012, and MAE is 1.11. CBA fluctuation implies fault spread. Faults serve as water flow conduits and channels, increasing the risk of infiltration. Meanwhile, cracks are being distributed as conduits and for infiltration. This research forms the basis for developing and increasing geothermal production so that further studies are needed regarding the influence of geological structures for reservoir in geothermal areas.

Magnesium and groundwater flow relationship in karst aquifers: a tool for exploitation management of springs

Karst aquifers are characterized by different types of groundwater flow, related to different types of permeability due to the simultaneous presence of matrix, fractures and conduits. The presence of a well-developed karst conduit system leads to a rapid circulation of groundwater within the aquifer and a pulse-type response of the spring flow to the rainfall inputs, with a potential fast transport of contaminants from the hydrogeological basin surface to the discharge zones. Supported by hydro chemical analyses of spring water samples and single discharge measurements, it was possible to develop specific mass balance models, correlating ion content to spring flowrates. Specifically, Mg2+ content revealed a reliable application for spring baseflow separation in karst settings. Once the local model has been set, its conservative behaviour, in mostly limestone-dominant aquifers, allows using Mg2+ as a natural tracer of groundwater flow, distinguishing conduit flow (overflow) and diffuse flow (baseflow) occurrence in the spring outlet, without additional discharge measurements. In karst settings, the difficulty in continuously monitoring the spring discharge values makes this application interesting for exploitation management. This study shows the results obtained for two springs located in Central Italy, confirming that monitoring groundwater quality in karst environments is often the key for successfully characterizing springs and assessing the total yield when direct measurements are not available.

Effects of Geometry on Artificial Tracer Dispersion in Synthetic Karst Conduit Networks

This paper presents the modeling results of tracer test simulations performed using COMSOL Multiphysics (version 6.1), a powerful software for multiphysics simulation. The simulations consist of the propagation of artificial tracers injected into different model configurations. This study is based on computational fluid dynamics (CFDs), which allows us to take into consideration the turbulent regime of the water flow in conduits. The objective of this contribution is to identify the relationship between the tracer dynamics and the geometric parameters of synthetic karstic systems via a systematic investigation of the occurrence of dual-peaked breakthrough curves (BTCs) in tracer tests. Various conduit structures were proposed by modifying five key factors: conduit diameter, presence of pools, connection angle between conduits, distance of the outlet from the inlet, and number of branches. The next step will be to confront these computational experiments with real-world tracer test experiments.