Abstract This study enhances the understanding of riverbank filtration and improves management of the Mississippi River valley alluvial (MRVA) aquifer during a managed aquifer recharge (MAR) pilot project at Shellmound, MS. Using high‐resolution electrical resistivity tomography (ERT) and self‐potential (SP) geophysical methods, we characterized the heterogeneous MRVA aquifer and monitored groundwater flow near a pumping well. ERT was used to provide detailed spatial characterization, filling gaps left by airborne electromagnetic (AEM) data and soil boring logs, while SP techniques were used to monitor groundwater flow, predict drawdown trends, and investigate surface‐groundwater interactions. Results showed that SP signals were influenced by groundwater flow, river infiltration, and water mixing due to pumping disturbance of natural geochemical stratification, with significant river interaction observed after 1 h of pumping. The integration of ERT and SP methods revealed lithologic heterogeneity, explaining greater drawdowns on the northern side of the well and increased flow from the riverside. This comprehensive approach offers valuable insights into aquifer management and sustainability.

Md Lal Mamud

Robert M. Holt

Craig J. Hickey

Andrew M. O'Reilly

Leti T. Wodajo

Parsa Bakhtiari Rad

Md Abdus Samad

Ground Water

Integrating <scp>ERT</scp> and <scp>SP</scp> Techniques for Characterizing Aquifers and Surface‐Groundwater Interactions

整合ERT和SP技术用于表征含水层及地表-地下水相互作用

Jeeban Panthi

Rachel Spinti

Exploring Freshwater Beneath the Ocean Floor

探索海底淡水资源

The data that support the findings of this study are openly available in Faculty of Engineering Repository at https://aquiparameter.ingenieria.unam.mx/.

Héctor Baez‐Reyes

Antonio Hernández‐Espriú

<scp>AquiParameter</scp>—A Novel Interactive Web‐Based Tool for Statistical Assessment of Hydrogeological Parameters

<scp>AquiParameter</scp>——一种用于水文地质参数统计评估的新型交互式网络工具

Abstract Research into land subsidence caused by groundwater withdrawal is hindered by the availability of measured heads, subsidence, and forcings. In this paper, a parsimonious, linked data‐driven and physics‐based approach is introduced to simulate pumping‐induced subsidence; the approach is intended to be applied at observation well nests. Time series analysis using response functions is applied to simulate heads in aquifers. The heads in the clay layers are simulated with a one‐dimensional diffusion model, using the heads in the aquifers as boundary conditions. Finally, simulated heads in the layers are used to model land subsidence. The developed approach is applied to the city of Bangkok, Thailand, where relatively short time series of head and subsidence measurements are available at or near 23 well nests; an estimate of basin‐wide pumping is available for a longer period. Despite the data scarcity, data‐driven time series models at observation wells successfully simulate groundwater dynamics in aquifers with an average root mean square error (RMSE) of 2.8 m, relative to an average total range of 21 m. Simulated subsidence matches sparse (and sometimes very noisy) land subsidence measurements reasonably well with an average RMSE of 1.6 cm/year, relative to an average total range of 5.4 cm/year. Performance is not good at eight out of 23 locations, most likely because basin‐wide pumping is not representative of localized pumping. Overall, this study demonstrates the potential of a parsimonious, linked data‐driven, and physics‐based approach to model pumping‐induced subsidence in areas with limited data.

Jenny T. Soonthornrangsan

Mark Bakker

Femke C. Vossepoel

Linked Data‐Driven, Physics‐Based Modeling of Pumping‐Induced Subsidence with Application to Bangkok, Thailand

基于链接数据的物理驱动抽水沉降建模及其在泰国曼谷的应用

Numerical modeling offers a valuable alternative to analytical solutions for pumping test analysis. However, little is known about how discretization impacts results accuracy and runtime. This study presents a systematic method for defining the spatiotemporal discretization of pumping test numerical models based on dimensionless parameters. Two types of analysis are considered: one where observations are made in the pumping well, and another one where observations are made in different wells. The influence of the discretization parameters on results accuracy and runtime is investigated and an optimal set of parameters is determined that minimizes runtime while maintaining the maximum error under 1% for an "average" aquifer. Lower runtimes are achieved when the analysis focuses on the pumping well, which is attributed to the steady-state analytical solution approximating drawdown in the well in the numerical scheme employed. Additional tests demonstrate the robustness of the derived set of parameters in different configurations.

Ronny Figueroa

Etienne Bresciani

A Close‐to‐Optimal Discretization Strategy for Pumping Test Numerical Simulation

一种接近最优的抽水试验数值模拟离散化策略

Abstract Automated water level measurements collected using vented pressure transducers in deep wells screened across the water table may exhibit a greater response to barometric pressure changes than the true water level. The cause was hypothesized to be disequilibrium in barometric pressure between the wellbores and land surface due to air exchange with the deep vadose zone. In this study, vented and nonvented pressure transducers were installed and operated simultaneously in two deep wells screened across the water table. A vent tube open to the atmosphere at land surface allowed for barometric compensation of the vented transducers. Two nonvented transducers were installed in each well, one submerged in the water and one above the water surface. The difference in readings allowed for barometric compensation. Manual measurements were also collected. It was confirmed that measurements from the vented transducers exhibited greater variability in response to barometric pressure changes than the nonvented transducers and manual measurements. Comparison of the downhole barometric pressure measurements to values from a nearby meteorology station showed the response in the wells to changes in barometric pressure was time‐lagged and attenuated. Thus, the reference pressure from land surface supplied to the vented transducers was not representative of the air pressure within the wells. This caused fluctuations of the transducer readings in response to barometric pressure changes to be greater than the true water level change. This issue can be resolved by the use of nonvented pressure transducers.

John P. McDonald

Pressure Transducer Measurement Variability in Deep Wells Screened Across the Water Table

深井中跨水位压力传感器测量变异性

Groundwater serves as a vital source of drinking water for millions of people worldwide. In the United States, a substantial population depends on groundwater for household purposes, including drinking, and therefore, ensuring a clean and safe water supply is imperative to preventing a wide range of human and nonhuman diseases. Biological and chemical water contamination causes diseases—both major and minor. In this issue's media spotlight column, we review the film Erin Brockovich (2000). It is based on the true events in Hinkley, CA, whose residents suffered from several waterborne diseases caused by anthropogenic heavy metal poisoning; a topic more relevant today than it was 25 years ago. The film's protagonist Erin Brockovich, the eponymous legal clerk working on a pro bono case connected threatening diseases in local residents to chromium poisoning in groundwater. She unearthed evidence that the source of the poisoning was unlined wastewater ponds in the Hinkley compressor station of Pacific Gas & Electric—a major energy company in California—that contained dissolved hexavalent chromium. About "370 million gallons of Cr(VI)-laden wastewater" was dumped in large unlined ponds from 1952 to 1964, which led to severe groundwater poisoning in an area of ~2 mile2. She almost single-handedly led the campaign against PG&E and educated the general masses about the harmful effects of chromium poisoning. The above conversation disseminates information regarding the types of chromium—chemically speaking, the different oxidation states of chromium—in groundwater. The audience is acutely made aware that their diseases can be passed along to their biological offspring as Cr(VI) can cause changes to DNA and mutagenesis. Cr(III) is not harmful because it is neither soluble in natural groundwater nor does it readily get absorbed in our bodies. Cr(VI), on the other hand, is very harmful because it can dissolve relatively easily in natural water that is usually alkaline and oxygen-rich. The Cr(VI) bearing chromate ion [CrVIO42−] can enter all cell types in the human body via active sulfate transporters owing to their similar structure. Cr(VI) can thus become a part of the human biochemical cycle and can mutate DNA structures, causing all sorts of diseases, including cancer. Once Cr(VI) enters the mammalian cell, it can get reduced to Cr(III), which binds directly with the DNA causing mutagenesis. The reduction of Cr(VI) can also produce unstable and highly reactive Cr(V) and Cr(IV) intermediates that are the source of further cellular damage in the human body. The availability, solubility, reactivity, and toxicity of different heavy metals are strongly controlled by their oxidation states. We believe that the movie accurately describes and educates its audiences on the effects of the oxidation state and demonstrates how nuanced discussion of scientific information is sometimes misused and convoluted to blind people who are not experts. Aqueous geochemists who study elements in aqueous systems and their chemical properties at different oxidation states as a function of solution acidity (aka pH) and oxidizing nature (aka Eh) would find the film interesting. In 1996, PG&E paid $333 million to settle the lawsuit—the largest amount ever paid in any direct-action lawsuit in the United States—and was mandated to remediate the contamination by converting soluble Cr(VI) to insoluble Cr(III) by injecting ethyl alcohol in the groundwater. In 2012, the amount of hexavalent chromium in the groundwater remained more than the interim regulatory background concentration. The U.S. Geological Survey recently submitted a report that reassessed the natural background and anthropogenic levels of Cr(VI) of different areas of Hinkley Valley by studying geologic, geochemical, and hydrologic processes that the local water board will use to establish regulatory background concentrations. The findings of this 5-year study pointed out that Cr(VI) in alkaline, oxic groundwater in the Hinkley Valley is dependent on a combination of geological and anthropological factors, including local mineralogy, weathering and oxidation rates, aquifer textures, fluid Eh-pH, and groundwater age. After 25 years since its release, Erin Brockovich still remains relevant and a trailblazer in promulgating awareness about hexavalent chromium in water. The film and Erin herself have raised awareness in the United States regarding several other environmentally related issues and have demonstrated that such incidents can disproportionately affect marginalized communities, exacerbating existing inequalities. Some other movies that have tackled groundwater contamination include Dark Waters (2019), A Civil Action (1995), and Irada (transl. Intention) (2017). We encourage our readers to (re)watch these movies and Julia Roberts in her Academy Award-winning performance in and as Erin Brockovich.

Priyanka Sharma

Kaushik Mitra

Hexavalent Chromium Contamination in Groundwater: <i>Erin Brockovich</i> Promulgating Awareness Since 2000

六价铬地下水污染：《永不妥协》自2000年以来推动公众意识

Abstract Many sedimentary aquifers consist of small layers of coarser and finer material. When groundwater flow in these aquifers is modeled, the hydraulic conductivity may be simulated as homogeneous but anisotropic throughout the aquifer. In practice, the anisotropy factor, the ratio of the horizontal divided by the vertical hydraulic conductivity, is often set to 10. Here, numerical experiments are conducted to determine the effective anisotropy of an aquifer consisting of 400 horizontal layers of which the homogeneous and isotropic hydraulic conductivity varies over two orders of magnitude. Groundwater flow is simulated to a partially penetrating canal and a partially penetrating well. Numerical experiments are conducted for 1000 random realizations of the 400 layers, by varying the sequence of the layers, not their conductivity. It is demonstrated that the effective anisotropy of the homogeneous model is a model parameter that depends on the flow field. For example, the effective anisotropy for flow to a partially penetrating canal differs from the effective anisotropy for flow to a partially penetrating well in an aquifer consisting of the exact same 400 layers. The effective anisotropy also depends on the sequence of the layers. The effective anisotropy values of the 1000 realizations range from roughly 5 to 50 for the considered situations. A factor of 10 represents a median value (a reasonable value to start model calibration for the conductivity variations considered here). The median is similar to the equivalent anisotropy, defined as the arithmetic mean of the hydraulic conductivities divided by the harmonic mean.

Bram Bot

The Effective Vertical Anisotropy of Layered Aquifers

层状含水层有效垂向各向异性

As readers of Groundwater, you have all faced a quizzical look when you told someone that you are a hydrogeologist. You have discovered that simply repeating the word—although, after all, it describes itself—is rarely sufficient. So, you have developed your own short explanation for what a hydrogeologist does and why our work is critical to society (one of my favorite is, "You know that water you drank yesterday? You're welcome."). If you are in a position to hire an entry-level professional hydrogeologist, you are likely to share something else: a growing concern that there are not enough graduates to fill current demand, let alone future needs for our profession. In summary, the future of hydrogeology is bright, but we are not producing enough MS-level trained students even to meet the current demand. In addition, universities are moving away from their role as the principal source of master's graduates and are unlikely to fill the future needs of industry or academia. The good news is that there are several efforts in progress to address this problem. Some programs (e.g., the University of Neuchatel) have strong enrollment and continue to produce graduates. Other programs are coming together to offer multi-university degrees (e.g., the European ERASMUS+ cooperation project iNUX). In addition, there are efforts to redesign the university-based MS to deliver accessible in-person (e.g., the University of Arizona) or hybrid in-person/online programs (e.g., the University of Kansas and the University of Waterloo). There are also extra-university programs that focus on advanced topics (e.g., the Italian SYMPL School of Hydrogeologic Modeling). Finally, there are efforts to make videos and textbooks available for free to support educational programs (e.g., the micro-video project, the Groundwater Modeling for Decision Support Initiative, and the Groundwater Project). We need all of these efforts to succeed if we hope to produce the workforce that will be needed in the future. However, there is a crucial first step that we need to complete as a community to ensure that future students are receiving the training that they need to enter the profession. This is where we need your help as groundwater professionals. Thank you for being part of the Groundwater community and I hope to work with you to advance our profession into the future!

Ty Ferre

<scp>MS</scp> Students Are the Missing Link in the Future of Hydrogeology – And How You Can Help!

<scp>MS</scp>学生是水文地质学未来的缺失环节——以及你如何能提供帮助！

Abstract Streamflow records are biased toward large streams and rivers, yet small headwater streams are often the focus of ecological research in response to climate change. Conventional flow measurement instruments such as acoustic Doppler velocimeters (ADVs) do not perform well during low‐flow conditions in small streams, truncating the development of rating curves during critical baseflow conditions dominated by groundwater inflow. We revisited an instantaneous solute tracer injection method as an alternative to ADVs based on paired measurements to compare their precision, efficiency, and feasibility within headwater streams across a range of flow conditions. We show that the precision of discharge measurements using salt dilution by slug injection and ADV methods were comparable overall, but salt dilution was more precise during the lowest flows and required less time to implement. Often, headwater streams were at or below the depth threshold where ADV measurements could even be attempted and transects were complicated by coarse bed material and cobbles. We discuss the methodological benefits and limitations of salt dilution by slug injection and conclude that the method could facilitate a proliferation of streamflow observation across headwater stream networks that are highly undersampled compared to larger streams.

Karli M. Rogers

Jennifer B. Fair

Nathaniel P. Hitt

Karmann G. Kessler

Zachary A. Kelly

Martin Briggs

Utility of an Instantaneous Salt Dilution Method for Measuring Streamflow in Headwater Streams

瞬时盐溶液稀释法在测定源头溪流流量中的应用

《地下水》是专注于地下水的领先国际期刊。自 1963 年以来，GROUND WATER 发表了一系列与地下水相关的论文，包括地下水流动和井水力学、水文地球化学和污染物水文地质学、地球物理学应用、地下水管理和政策以及地下水水文学史。这是您可以信赖的期刊，可为您带来地下水水文学中的实际应用。

GROUND WATER is a leading international journal focused on groundwater research. Since its inception in 1963, GROUND WATER has published a wide range of papers related to groundwater, including studies on groundwater flow and well hydraulics, hydrogeochemistry and contaminant hydrogeology, applications of geophysics, groundwater management and policy, as well as the history of groundwater hydrology. This is a trusted journal that provides practical applications in the field of groundwater hydrology.

《地下水》是一本专注于地下水研究的国际领先期刊。自1963年以来，GROUND WATER发表了大量与地下水相关的研究论文，涵盖了地下水流动与井水力学、水文地球化学与污染物水文地质学、地球物理学应用、地下水管理与政策，以及地下水水文学的历史等领域。这是一本值得信赖的期刊，为您提供地下水水文学的实际应用研究。

期刊	Ground Water
ISSN	0017-467X, 1745-6584
h-index	110
Journal Impact	2.19
国际分区	WATER RESOURCES(Q3)
国内分区	地球科学(4区)地球科学地球科学综合(4区)地球科学水资源(4区)