Ground Water[JOURNAL]
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200 papers
Evaluating Flow Distribution in a Multiaquifer Recharge Well Using an In Situ Flowmeter.
Martinez MB, Widdowson MA
Ground Water · 2024 · PMID 38084658 · Publisher ↗
Quantifying the flow rate distribution in a multiple-screen recharge well is relevant to understanding groundwater flow and solute transport behavior in managed aquifer recharge (MAR) operations. In this study, an impell...
Quantifying the flow rate distribution in a multiple-screen recharge well is relevant to understanding groundwater flow and solute transport behavior in managed aquifer recharge (MAR) operations. In this study, an impeller flowmeter was deployed to measure flow rate distribution in a multiple-screen MAR well under both recharge and pumping conditions screened in the multiple-strata of the Virginia Coastal Plain aquifer system. Preferential flow distribution in the well was observed through the uppermost screens during recharge while flow distribution was more evenly distributed along all screens under pumping conditions. Analysis of flow along individual screens also indicates preferential flow to the upper part of the screen during both recharge and pumping. Comparison of flowmeter results under both recharge and pumping conditions to previous site-specific measurements suggests that the distribution of flow may vary with time, depending on well screen condition and well rehabilitation efforts, and should be monitored over the duration of an MAR project. These results have implications for groundwater quality given that flow distribution in a multiscreen recharge well has profound impact on travel time and on transport modeling if flow is assumed to be steady and consistent under a range of operational conditions.
An Iterative Method of Modeling Pump-Treat-Inject System with "Partial Treatment".
Zhang J, Zhang Y, Schwartz FW … +1 more , Karimi M
Ground Water · 2024 · PMID 38061892 · Publisher ↗
Pump-and-treat technologies are widely used in groundwater remediation and site cleanup. Such technologies involve pumping contaminated groundwater to the surface for treatment. Following treatment, the water is often re...
Pump-and-treat technologies are widely used in groundwater remediation and site cleanup. Such technologies involve pumping contaminated groundwater to the surface for treatment. Following treatment, the water is often reinjected back into the aquifer (referred to as pump-treat-inject or PTI) for potential reuse. The treatment system is often designed to remove dissolved-phase contaminants in groundwater such that water meets applicable cleanup standards (herein referred to as "full treatment"). However, in some cases, the treatment system may not effectively reduce the dissolved-phase concentrations (herein referred to as "partial treatment") for some of the contaminants present in groundwater. Modeling PTI under partial treatment conditions is challenging because contaminant concentrations in injected water depend on the pumped water concentrations and the system treatment efficiency. Essentially, the injected water concentration (a transport model input) is unknown prior to transport simulation. This study presents a novel iterative approach to modeling PTI under partial treatment scenarios, where the injected water concentration is linked to the modeled pumped water concentration. The method was developed for a complicated three-dimensional (3D) flow and transport modeling study conducted for a confidential remediation site where PTI with partial treatment was applied. However, due to the complexity of the 3D model and the confidential information of the site, a simple two-dimensional (2D) numerical model is presented to demonstrate the iterative method. The 2D model test runs and the 3D model application in a remediation site showed that the iterative simulation results quickly converged to a viable final solution.
New Insights into the Formation and Properties of Wellbore Skin: Why We Have to Rethink the Concept.
Houben GJ, Lamparter A, Ufer K … +2 more , Damian C, Boz D
Ground Water · 2024 · PMID 38039098 · Publisher ↗
The deposition of fine-grained material of low permeability on the borehole wall during drilling (wellbore skin) is a common problem affecting the operation and efficiency of water wells. Here, we present new data and no...
The deposition of fine-grained material of low permeability on the borehole wall during drilling (wellbore skin) is a common problem affecting the operation and efficiency of water wells. Here, we present new data and novel insights from four excavated dewatering wells from a lignite surface mine. All wells have the same age, are of similar construction, and were sampled at two different depths each. The thickness of the skin layer increases with depth. Its composition and permeability is strongly influenced by the surrounding aquifer material. Nonuniform sediments of low permeability result in less permeable wellbore skin deposits. The presence of discontinuities in the skin layer may be a determining feature for the resulting flow to wells, especially with skin layers of low permeability. The presence of naturally occurring swelling clay (smectite) provides the skin layer with a significant self-sealing capacity.
Groundwater for People and the Environment: A Globally Threatened Resource.
Loaiciga HA, Doh R
Ground Water · 2024 · PMID 37989720 · Publisher ↗
The intensity of global groundwater use rose from 124 m per capita in 1950 to 152 m in 2021, for a 22.6% rise in the annual per capita use. This rise in global per capita water use reflects rising consumption patterns. T...
The intensity of global groundwater use rose from 124 m per capita in 1950 to 152 m in 2021, for a 22.6% rise in the annual per capita use. This rise in global per capita water use reflects rising consumption patterns. The global use of groundwater, which provides between 21% and 30% of the total freshwater annual consumption, will continue to expand due to the sustained population growth projected through most of the 21st century and the important role that groundwater plays in the water-food-energy nexus. The rise in groundwater use, on the other hand, has inflicted adverse impacts in many aquifers, such as land subsidence, sea water intrusion, stream depletion, and deterioration of groundwater-dependent ecosystems, groundwater-quality degradation, and aridification. This paper projects global groundwater use between 2025 and 2050. The projected global annual groundwater withdrawal in 2050 is 1535 km (1 km = 10 m = 810,713 acre-feet). The projected global groundwater depletion, that is, the excess of withdrawal over recharge, in 2050 equals 887 km, which is about 61% larger than in 2021. This projection signals probable exacerbation of adverse groundwater-withdrawal impacts, which are worsened by climatic trends and the environmental requirement of groundwater flow unless concerted national and international efforts achieve groundwater sustainability.
Impact of Type and Shape of Microplastics on the Transport in Column Experiments.
Schenkel CA, Brown MRM, Lenczewski ME
Ground Water · 2024 · PMID 37983834 · Publisher ↗
The pervasive nature of plastic and the longevity of plastics leaves a legacy of microplastics (MPs) that contaminate our environment, including drinking water sources. Although MPs have been documented in every environm...
The pervasive nature of plastic and the longevity of plastics leaves a legacy of microplastics (MPs) that contaminate our environment, including drinking water sources. Although MPs have been documented in every environmental setting, a paucity of research has focused on the transport and fate of MPs in groundwater. Previous field and laboratory studies have shown that MPs can migrate through aquifer material and are influenced by environmental factors. This study used controlled column experiments to investigate the influence of polymer type (polyamide, polyethylene, polypropylene, and polyester) and particle shape (fragment, fiber, and sphere) on MP retardation and retention. The results showed that all individual MP types investigated were retarded compared to the NaCl tracer, with a retardation factor ranging from 1.53 to 1.75. While hypothesized that presence of multiple types and shapes could change mobility, the results indicate that this hypothesis is not correct for the conditions tested. This study provides new insights into MP transport in groundwater systems based on the characteristics of MP particles. In addition, this study demonstrates the need for further research on types of MPs and under more conditions, especially in the presence of a mixture of types and shapes of MPs to gauge what is occurring in natural systems where many MPs are present together.
Towards Improved Remedial Outcomes in Categorical Aquifers with an Iterative Ensemble Smoother.
Khambhammettu P, Renard P, Doherty J … +3 more , White J, Killingstad M, Kladias M
Ground Water · 2024 · PMID 37945376 · Publisher ↗
Categorical parameter distributions consisting of geologic facies with distinct properties, for example, high-permeability channels embedded in a low-permeability matrix, are common at contaminated sites. At these sites,...
Categorical parameter distributions consisting of geologic facies with distinct properties, for example, high-permeability channels embedded in a low-permeability matrix, are common at contaminated sites. At these sites, low-permeability facies store solute mass, acting as secondary sources to higher-permeability facies, sustaining concentrations for decades while increasing risk and cleanup costs. Parameter estimation is difficult in such systems because the discontinuities in the parameter space hinder the inverse problem. This paper presents a novel approach based on Traveling Pilot Points (TRIPS) and an iterative ensemble smoother (IES) to solve the categorical inverse problem. Groundwater flow and solute transport in a hypothetical aquifer with a categorical parameter distribution are simulated using MODFLOW 6. Heads and concentrations are recorded at multiple monitoring locations. IES is used to generate posterior ensembles assuming a TRIPS prior and an approximate multi-Gaussian prior. The ensembles are used to predict solute concentrations and mass into the future. The evaluation also includes an assessment of how the number of measurements and the choice of the geological prior determine the characteristics of the posterior ensemble and the resulting predictions. The results indicate that IES was able to efficiently sample the posterior distribution and showed that even with an approximate geological prior, a high degree of parameterization and history matching could lead to parameter ensembles that can be useful for making certain types of predictions (heads, concentrations). However, the approximate geological prior was insufficient for predicting mass. The analysis demonstrates how decision-makers can quantify uncertainty and make informed decisions with an ensemble-based approach.
Borehole Nuclear Magnetic Resonance Estimation of Specific Yield in a Fractured Granite Aquifer.
Phillips SN, Carr B, Zhang Y … +2 more , Flinchum B, Ren S
Ground Water · 2024 · PMID 37930240 · Publisher ↗
In this study, we introduce a novel field-based method to estimate specific yield (S) in fractured, low-porosity granite aquifers using borehole nuclear magnetic resonance (bNMR). This method requires collecting a bNMR s...
In this study, we introduce a novel field-based method to estimate specific yield (S) in fractured, low-porosity granite aquifers using borehole nuclear magnetic resonance (bNMR). This method requires collecting a bNMR survey immediately following a pump test, which dewaters the near-borehole fractures. The residual water content measured from bNMR is interpreted as "bound" and represents the specific retention (S) while the water drained by the pump is the S. The transverse relaxation cutoff time (T) is the length of time that partitions the total porosity measured by bNMR into S and S. When applying a calibrated T, S equals the bNMR total porosity minus S; thus, a calibrated T is required to determine S directly from NMR results. Based on laboratory experiments on sandstone cores, the default T is 33 ms; however, its applicability to fractured granite aquifers is uncertain. The optimal T based on our pumping test is 110 ± 25 ms. Applying this calibrated T on a saturated, A-type granite at our field site, we estimate the S to be 0.012 ± 0.005 m m which is significantly different from the S (0.021 ± 0.005 m m) estimate using the default T of 33 ms. This S estimate falls within a range determined using traditional hydraulic testing at the same site. Using the conventional T (33 ms) for fractured granite leads to an inaccurate S; therefore, it is essential to calibrate the bNMR T for the local site conditions prior to estimating S.
Delineation of a PFOA Plume and Assessment of Data Gaps in its Conceptual Model Using PlumeSeeker™.
Ozbek M, Voorhies N, Howard L … +2 more , Swanson R, Fox T
Ground Water · 2024 · PMID 37930157 · Publisher ↗
An accurate conceptual site model (CSM) and plume-delineation at contamination sites are pre-requisites for successful remediation and for satisfying regulators and stakeholders. PlumeSeeker™ is well-suited for assessing...
An accurate conceptual site model (CSM) and plume-delineation at contamination sites are pre-requisites for successful remediation and for satisfying regulators and stakeholders. PlumeSeeker™ is well-suited for assessing data gaps in CSMs by using available site data and for identifying the optimal number and locations of sampling locations to delineate contaminant plumes. It is an enhancement of a university research code for plume delineation using geostatistical and stochastic modeling integrated with the groundwater modeling software MODFLOW-SURFACT™. PlumeSeeker™ increases the overall confidence in the location of the plume boundary through a variance-reduction approach that selects existing- or new monitoring wells for sampling based on minimizing the uncertainty in plume boundary and on new field information. Applicable at sites with or without existing monitoring wells, PlumeSeeker™ is particularly powerful for optimally allocating project resources (labor, well installation, and laboratory costs) between existing wells and sampling at new locations. An application of PlumeSeeker™ at Lakehurst, the naval component of Joint Base McGuire-Dix-Lakehurst in New Jersey, demonstrates how the cost of delineating the migration pathway of a perfluorooctanoic acid (PFOA) plume can be minimized by requiring only 9 new sampling locations in addition to samples from 2 existing wells for achieving a 70% reduction in plume uncertainty. In addition, the use of available site data in three different scenarios identified CSM data-gaps in the source area and in the interaction between Manapaqua Branch and groundwater, where the observed high concentration in this area could have resulted from a combination of groundwater migration and induced infiltration.
Hydrogeochemical Evaluation of Aquifer Storage and Recovery in Edwards Aquifer, New Braunfels, Texas.
Simbo CW
Ground Water · 2024 · PMID 37927180 · Publisher ↗
This study examines the potential for aquifer storage and recovery (ASR) in the brackish portion of the Edwards aquifer in New Braunfels, Texas. Successful ASR relies on understanding hydraulic properties, aquifer hetero...
This study examines the potential for aquifer storage and recovery (ASR) in the brackish portion of the Edwards aquifer in New Braunfels, Texas. Successful ASR relies on understanding hydraulic properties, aquifer heterogeneity, water geochemistry, and geochemical processes during operations. The research aims to investigate the chemistries of native groundwater and injectant during ASR operation, estimate the hydraulic properties of the aquifer layers, and assess the recovery rate for the recovered groundwater meeting the total dissolved solids (TDS) threshold. The study found that native groundwater is of Na-Cl facies due to halite dissolution and a possible basinal brine migration associated with the zone of greatest fault displacement. High sulfate ions in background native groundwater result from sulfate-bearing minerals' dissolution in the Kainer and Person Formations. The injectant water is of Ca-Mg-HCO facies due to the carbonate-rich composition of the aquifer host matrix and interaction with the Guadalupe River riverbed. During ASR operations, mixing controlled the shift in hydrochemical facies from Na-Cl to Ca-Mg-HCO.The study also suggests a possible connection between Kainer and Person Formations and preferential pathways in the targeted storage zone aquifer. The estimated conductivity values also indicate dominant horizontal flow via possible fracture pathways in both the Person and Kainer Formation storage zones. Recovery of groundwater meeting the TDS of 1000 mg/L requires a recovery rate of 0.03 m/s for 60 days after 40-day storage. This research emphasizes that understanding the hydrogeological conditions and geochemical processes is critical to ASR feasibility in brackish carbonate multi-aquifer fractured systems.
Effects of Auto-Adaptive Localization on a Model Calibration Using Ensemble Methods.
Traylor JP, Hunt RJ, White J … +1 more , Fienen MN
Ground Water · 2024 · PMID 37897310 · Publisher ↗
Abstract loading — click title to view on PubMed.
An Agricultural Package for MODFLOW 6 Using the Application Programming Interface.
Larsen JD, Langevin CD, Hughes JD … +1 more , Niswonger RG
Ground Water · 2024 · PMID 37882370 · Publisher ↗
An agricultural water use package has been developed for MODFLOW 6 using the MODFLOW Application Programming Interface (API). The MODFLOW API Agricultural Water Use Package (API-Ag) was based on the approach to simulate...
An agricultural water use package has been developed for MODFLOW 6 using the MODFLOW Application Programming Interface (API). The MODFLOW API Agricultural Water Use Package (API-Ag) was based on the approach to simulate irrigation demand in the MODFLOW-NWT and GSFLOW Agricultural Water Use (AG) Package. The API-Ag Package differs from the previous approach by implementing new features and support for additional irrigation providers. New features include representation of deficit and over-irrigation, Multi-Aquifer Well and Lake Package irrigation providers, and support for structured, vertex, and unstructured grid models. Three example problems are presented that demonstrate how the API-Ag Package improves representation of highly managed systems and are further used to validate the irrigation demand and delivery formulations. Irrigation volumes simulated in the three example problems show excellent agreement with the MODFLOW-NWT AG Package.
Approximation of van Genuchten Parameter Ranges from Hydraulic Conductivity Data.
Peche A, Houben G, Altfelder S
Ground Water · 2024 · PMID 37870086 · Publisher ↗
The use of retention function and relative conductivity function is essential for the calculation of flow in a variably saturated media using the Richards equation. A widely used mathematical model for this is the Mualem...
The use of retention function and relative conductivity function is essential for the calculation of flow in a variably saturated media using the Richards equation. A widely used mathematical model for this is the Mualem-van Genuchten model which requires the shape parameters and . These, however, are difficult to obtain. When data is scarce, and are often taken from literature and may deviate largely from actual values. The current study presents a novel mathematical model for the approximation of and and for the further estimation of realistic value ranges, which may be used as parameter space, for example, for the calibration of a numerical model. The model was developed for cases where data is scarce and only values of saturated hydraulic conductivity are available. It is based on a large data set from literature and it is demonstrated that the model estimates mean values from that data set with a good accuracy. In order to show the applicability of the model, a second data set has been compiled anew (provided as Supporting Information). The model is incorporated into the current version of the freeware computer program HYPAGS, which enables easy usage.
An Automatic-Vertical Profile Monitoring System for Fresh-Saline Water Zones in Coastal Aquifer.
Jeon WH, Moon HS, Choi J … +4 more , Jung B, Kim Y, Hwang S, Lee SH
Ground Water · 2024 · PMID 37847079 · Publisher ↗
Coastal aquifers are complex systems governed by fresh-saline water interactions and ocean tidal effects. The vertical electrical conductivity (EC) and temperature (T) are general indicators for detecting the fresh-salin...
Coastal aquifers are complex systems governed by fresh-saline water interactions and ocean tidal effects. The vertical electrical conductivity (EC) and temperature (T) are general indicators for detecting the fresh-saline water interface (FSI) and sea water intrusion in groundwater wells located in coastal aquifers. In this method brief, we developed a cost-effective Arduino-based automatic-vertical profile monitoring system (A-VPMS) to continuously record vertical EC and T in groundwater wells, with the aim of testing its effectiveness in spatiotemporal monitoring of the FSI in a coastal aquifer located in eastern Korea. By analyzing the high-density EC and T data obtained by the A-VPMS, we evaluated the characteristics of the FSI, such as depth and spatial distribution. Our established EC and T data collection method using the A-VPMS proved to be efficient and reliable, providing an excellent tool for fine-scale temporal and spatial understanding of sea water intrusion. The results of this study demonstrate the potential of the A-VPMS for continuous monitoring of the FSI in coastal aquifers, which is crucial for sustainable management of groundwater resources.
Water Table Depth Estimates over the Contiguous United States Using a Random Forest Model.
Ma Y, Leonarduzzi E, Defnet A … +3 more , Melchior P, Condon LE, Maxwell RM
Ground Water · 2024 · PMID 37797066 · Publisher ↗
Water table depth (WTD) has a substantial impact on the connection between groundwater dynamics and land surface processes. Due to the scarcity of WTD observations, physically-based groundwater models are growing in thei...
Water table depth (WTD) has a substantial impact on the connection between groundwater dynamics and land surface processes. Due to the scarcity of WTD observations, physically-based groundwater models are growing in their ability to map WTD at large scales; however, they are still challenged to represent simulated WTD compared to well observations. In this study, we develop a purely data-driven approach to estimating WTD at continental scale. We apply a random forest (RF) model to estimate WTD over most of the contiguous United States (CONUS) based on available WTD observations. The estimated WTD are in good agreement with well observations, with a Pearson correlation coefficient (r) of 0.96 (0.81 during testing), a Nash-Sutcliffe efficiency (NSE) of 0.93 (0.65 during testing), and a root mean square error (RMSE) of 6.87 m (15.31 m during testing). The location of each grid cell is rated as the most important feature in estimating WTD over most of the CONUS, which might be a surrogate for spatial information. In addition, the uncertainty of the RF model is quantified using quantile regression forests. High uncertainties are generally associated with locations having a shallow WTD. Our study demonstrates that the RF model can produce reasonable WTD estimates over most of the CONUS, providing an alternative to physics-based modeling for modeling large-scale freshwater resources. Since the CONUS covers many different hydrologic regimes, the RF model trained for the CONUS may be transferrable to other regions with a similar hydrologic regime and limited observations.
Urban Thirst and Rural Water: The Saga of the Southern Nevada Groundwater Development Project.
Jones NL, Mayo AL
Ground Water · 2024 · PMID 37793027 · Publisher ↗
In 1989, the Southern Nevada Water Authority (SNWA) launched the Southern Nevada Groundwater Development Project-a bold plan to construct a series of deep wells in east-central Nevada to pump groundwater and send it to t...
In 1989, the Southern Nevada Water Authority (SNWA) launched the Southern Nevada Groundwater Development Project-a bold plan to construct a series of deep wells in east-central Nevada to pump groundwater and send it to the Las Vegas region through 300 miles of pipeline. Before starting work on the project, SNWA conducted an environmental impact study and secured water rights in the valleys. Applications for additional new water rights were filed with Nevada State Engineer on the basis of uncaptured evapotranspiration. The SNWA spent decades and millions of dollars studying the hydrogeology of the region and developing computer models to demonstrate that the project would not have an unduly negative impact on the ecology or water users in the region. The project was opposed by environmental groups, native American tribes, and existing water rights holders. One of the protestants was the Cleveland Ranch in Spring Valley. Using the SNWA's own groundwater model, the ranch argued that the project would result in substantial harm to the ranch's water rights which included springs, wells, and a stream, and that the project would result in perpetual groundwater mining, which is forbidden by Nevada state policy. The Nevada State Engineer approved the project, but the decision was eventually reversed by Seventh District Court, which sided with the ranch and ruled that the project would never be sustainable and is therefore not compatible with Nevada policy. The project was formally abandoned in 2020.
Use of Hydrogeochemistry and Isotopes for Evaluation of Groundwater in Qilian Coal Base of China.
Zhao C, Li X, Wang Z … +2 more , Hou X, Ma J
Ground Water · 2024 · PMID 37787624 · Publisher ↗
The Jiangcang Basin is an important mining area of the former Qilian Mountain large coal base in Qinghai Province, and understanding the groundwater circulation mechanism is the basis for studying the hydrological effect...
The Jiangcang Basin is an important mining area of the former Qilian Mountain large coal base in Qinghai Province, and understanding the groundwater circulation mechanism is the basis for studying the hydrological effects of permafrost degradation in alpine regions. In this study, hydrogeochemical and multiple isotope tracer analysis methods are used to understand the chemical evolution and circulation mechanisms of the groundwater in the typical alpine region of the Jiangcang Basin. The diversity of the groundwater hydrochemistry in the study area reflects the complexity of the hydrogeochemical environment in which it is located. The suprapermafrost water and intrapermafrost water are recharged by modern meteoric water. The groundwater is closely hydraulically connected to the surface water with weak evaporation overall. The high δS value of deep groundwater is due to SO reduction, and SO -rich snow recharge with lixiviated sulfate minerals are the main controlling factor for the high SO concentration in groundwater. According to the multivariate water conversion relationships, it reveals that the river receives more groundwater recharge, suprapermafrost water is recharged by the proportion of meteoric water, which is closely related to the mountainous area at the edge of the basin, while intrapermafrost water is mainly recharged by the shallow groundwater. This study provides a data-driven approach to understanding groundwater recharge and evolution in alpine regions, in addition to having significant implications for water resource management and ecological environmental protection in coal bases of the Tibetan Plateau.
What Can Groundwater Monitoring Tell Us About Gas Migration? A Numerical Modeling Study.
Jain K, Van De Ven CJC, Mayer KU
Ground Water · 2024 · PMID 37779366 · Publisher ↗
Groundwater monitoring to measure a variety of indicator parameters including dissolved gas concentrations, total dissolved gas pressure (TDGP), and redox indicators is commonly used to evaluate the impacts of gas migrat...
Groundwater monitoring to measure a variety of indicator parameters including dissolved gas concentrations, total dissolved gas pressure (TDGP), and redox indicators is commonly used to evaluate the impacts of gas migration (GM) from energy development in shallow aquifer systems. However, these parameters can be challenging to interpret due to complex free-phase gas source architecture, multicomponent partitioning, and biogeochemical reactions. A series of numerical simulations using a gas flow model and a reactive transport model were conducted to delineate the anticipated evolution of indicator parameters following GM in an aquifer under a variety of physical and biogeochemical conditions. The simulations illustrate how multicomponent mass transfer processes and biogeochemical reactions create unexpected spatial and temporal variations in several analytes. The results indicate that care must be taken when interpreting measured indicator parameters including dissolved hydrocarbon concentrations and TDGP, as the presence of dissolved gases in background groundwater and biogeochemical processes can cause potentially misleading conclusions about the impact of GM. Based on the consideration of multicomponent gas partitioning in this study, it is suggested that dissolved background gases such as N and Ar can provide valuable insights on the presence, longevity and fate of free-phase natural gas in aquifer systems. Overall, these results contribute to developing a better understanding of indicators for GM in groundwater, which will aid the planning of future monitoring networks and subsequent data interpretation.
A Low-Cost Programmable Reversing Flow Column Apparatus for Investigating Mixing Zones.
Buskirk RE, Knappett PSK, Cardenas MB … +3 more , Datta S, Borowski WS, Mendoza-Sanchez I
Ground Water · 2024 · PMID 37776269 · Publisher ↗
This note describes the development and testing of a novel, programmable reversing flow 1D (R1D) experimental column apparatus designed to investigate reaction, sorption, and transport of solutes in aquifers within dynam...
This note describes the development and testing of a novel, programmable reversing flow 1D (R1D) experimental column apparatus designed to investigate reaction, sorption, and transport of solutes in aquifers within dynamic reversing flow zones where waters with different chemistries mix. The motivation for constructing this apparatus was to understand the roles of mixing and reaction on arsenic discharging through a tidally fluctuating riverbank. The apparatus can simulate complex transient flux schedules similar to natural flow regimes The apparatus uses an Arduino microcontroller to control flux magnitude through two peristaltic pumps. Solenoid valves control flow direction from two separate reservoirs. In-line probes continually measure effluent electrical conductance, pH, oxidation-reduction potential, and temperature. To understand how sensitive physical solute transport is to deviations from the real hydrograph of the tidally fluctuating river, two experiments were performed using: (1) a simpler constant magnitude, reversing flux direction schedule (RCF); and (2) a more environmentally relevant variable magnitude, reversing flux direction schedule (RVF). Wherein, flux magnitude was ramped up and down according to a sine wave. Modeled breakthrough curves of chloride yielded nearly identical dispersivities under both flow regimes. For the RVF experiment, Peclet numbers captured the transition between diffusion and dispersion dominated transport in the intertidal interval. Therefore, the apparatus accurately simulated conservative, environmentally relevant mixing under transient, variable flux flow regimes. Accurately generating variable flux reversing flow regimes is important to simulate the interaction between flow velocity and chemical reactions where Brownian diffusion of solutes to solid-phase reaction sites is kinetically limited.
Hydrogeological Functioning of a Karst Underground River Basin in Southwest China.
Guo Y, Huang F, Sun P … +4 more , Zhang C, Xiao Q, Wen Z, Yang H
Ground Water · 2023 · PMID 37776229 · Publisher ↗
The Maocun underground karst river system in the peak cluster depression is an important source of groundwater in southwest China. Multitracers and high resolution water-level-monitoring technology were used to assess an...
The Maocun underground karst river system in the peak cluster depression is an important source of groundwater in southwest China. Multitracers and high resolution water-level-monitoring technology were used to assess and evaluate the hydrogeological structure and flow dynamics. The results showed that the spatial geological structures of the sites had high heterogeneity. Scatter plots of environmental tracers divided the sampling points into groups under different water flow patterns. The karstification was found to increase from sites XLB and LLS to sites BY, SGY and BDP to sites CY and DYQ, where the main water flow patterns at these site groups were diffuse water, both diffuse water and conduit water, and conduit water, respectively. The response times of the subsystems were found to be influenced by the spatial structure, the degree of karstification, and the volume of precipitation and frequency. The average response times of SGY, BDP, ZK, and Outlet in the selected precipitation scenarios were 5.17, 4.08, 16.42, and 5.83 h, respectively. In addition, the EC, δ C , Rn, and δ O exhibited both linear or exponential relationships. Overall, three hydrogeological conceptual models were constructed showing: (1) high precipitation driving the deep water, resulting in a concentrated flow regime and regional groundwater flow field; (2) both concentrated and diffuse water flows existing under moderate precipitation, resulting in mixed water flow field; (3) the water cycle in the shallow karst aquifer system under low precipitation causing the local groundwater flow field to be dominated by diffuse water flow.
Learning Theories Applied to Teaching and Improving Hydrogeological Conceptualization.
Brown S, Bornasal F
Ground Water · 2023 · PMID 37773587 · Publisher ↗
Conceptual change is the process of developing a new understanding of an idea or related set of ideas and has been researched and theorized extensively in the last few decades. Although there is ongoing debate about how...
Conceptual change is the process of developing a new understanding of an idea or related set of ideas and has been researched and theorized extensively in the last few decades. Although there is ongoing debate about how and why conceptual change occurs, all agree that individuals' prior knowledge plays a role, everyone engages differently in the process, and the context of the learning environment is influential. In this paper we build upon the work explored by Jimenez-Martinez (this issue) on conceptual change in hydrogeology, and explore how the conceptual change theory of Vosniadou may facilitate understanding the learning process in hydrogeology. Vosniadou's theory is particularly applicable because it addresses the learning of ideas that combine abstract (GW flow) and visible (water flow) concepts. A pathway for exploring hydrogeology students' mental models (from naïve framework theory, to synthetic models, to scientific mental models) and identifying misconceptions specifically within hydrogeology using methods established by Vosniadou and colleagues is proposed as a means to address some of the challenges identified by Jimenez-Martinez.
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