GroundwaterPub Date : 2026-09-13Epub Date: 2026-05-28DOI: 10.1111/gwat.70082
Rui Hugman, Jeremy White
{"title":"Python-Based Model Emulation Workflows with PEST","authors":"Rui Hugman, Jeremy White","doi":"10.1111/gwat.70082","DOIUrl":"10.1111/gwat.70082","url":null,"abstract":"<p>Computational demands for uncertainty quantification and optimization often exceed available resources for high-fidelity environmental models. While surrogate modeling (or model emulation) offers a pragmatic solution, widespread adoption is hindered by a significant “implementation gap”: practitioners often lack standardized, robust tools to integrate emulation techniques directly into existing modeling workflows, relying instead on bespoke implementations. To bridge this gap, we present the Emulator module within the open-source pyEMU package. This framework provides a “plug-and-play” architecture for deploying Gaussian Process Regression (GPR), Data-Space Inversion (DSI) and other model emulation approaches. The framework automates the complex “plumbing” of emulation-based workflows, including non-Gaussian data transformation and the generation of PEST interface files, allowing trained surrogates to serve as drop-in replacements for physics-based models. We believe this one-to-one correspondence between physics-based model and emulator-based workflows will facilitate direct comparisons between the two so that the community in general can build up the knowledge of when and how to effectively and appropriately deploy emulation. We demonstrate the utility of these tools through a benchmarking optimization problem and a history-matching application on a synthetic groundwater model.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 5","pages":"669-680"},"PeriodicalIF":2.6,"publicationDate":"2026-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148045040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GroundwaterPub Date : 2026-09-13Epub Date: 2026-08-07DOI: 10.1111/gwat.70097
Yu-Feng F. Lin
{"title":"Groundwater in an Evolving Energy Landscape","authors":"Yu-Feng F. Lin","doi":"10.1111/gwat.70097","DOIUrl":"10.1111/gwat.70097","url":null,"abstract":"<p>For nearly a century, groundwater professionals have established groundwater as one of society's most valuable water resources. Today, another opportunity stands before us. Our community should consider broadening the definition of groundwater resources by recognizing one additional resource that groundwater has always provided—energy. In this editorial, “energy” does not refer to transforming groundwater into fuel or electricity, but to groundwater's natural capacity to store, transport, exchange, and recover thermal energy, which improves the efficiency, resilience, and sustainability of modern energy systems.</p><p>Most discussions about energy policy begin with electricity. Governments announce new generating capacity, utilities forecast future demand, and industries estimate how many gigawatts will be needed to support the artificial intelligence (AI) infrastructure, such as data centers, semiconductor manufacturing plants, and their supply chains. These discussions are necessary, but they represent only one side of the energy equation. The other side—how efficiently energy is stored, transported, utilized, and managed—is equally important. Most electricity ultimately becomes heat that must be removed, recovered, or stored. As society increasingly builds an energy-intensive infrastructure, thermal management is becoming as critical as generating electricity.</p><p>Groundwater offers capabilities that few other natural resources can provide. It occupies an enormous subsurface volume, maintains relatively stable temperatures throughout the year, and possesses one of the highest volumetric heat capacities among naturally abundant materials. A saturated system is not only an excellent thermal reservoir but also an effective thermal carrier if groundwater flow occurs. This combination of high heat capacity and natural convective heat transport gives saturated aquifer systems significant advantages over unsaturated or dry subsurface materials for geothermal exchange, underground thermal energy storage (UTES), district energy systems, and cooling of the AI infrastructure (Fleuchaus et al. <span>2018</span>; Pepin et al. <span>2025</span>). Furthermore, most modern UTES systems recirculate groundwater without water loss except for leakage.</p><p>Our profession has already been building the scientific foundation for these applications since the 1970s. The <i>Groundwater</i> Special Issue on <i>Advances in Thermal Use of Groundwater</i> documented the rapid maturation of groundwater thermal science (Lin et al. <span>2023</span>). Many coupled thermohydrologic models have been used since the 1980s, such as MULKOM, the TOUGH suite series, and many more. More recently, the Groundwater Energy (GWE) Model for MODFLOW 6 integrated groundwater flow and thermal energy transport into what is now the most widely used open-access groundwater simulation. Scientific advances often redefine how society values natural resources. The ability to quantify groundwate","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 5","pages":"532-533"},"PeriodicalIF":2.6,"publicationDate":"2026-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.70097","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148687188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GroundwaterPub Date : 2026-09-13Epub Date: 2026-08-15DOI: 10.1111/gwat.70098
G. Kourakos, H. Morel-Seytoux, E. C. Dogrul, T. Kadir, H. E. Dahlke
{"title":"Finite Element Implementation of SAFE for Asymmetric Stream-Aquifer Flow Exchange","authors":"G. Kourakos, H. Morel-Seytoux, E. C. Dogrul, T. Kadir, H. E. Dahlke","doi":"10.1111/gwat.70098","DOIUrl":"10.1111/gwat.70098","url":null,"abstract":"<p>Climate change and human activities increasingly affect interconnected stream–aquifer systems, motivating continued evaluation of how stream–aquifer interactions are represented in integrated groundwater–surface water models. Most groundwater models quantify stream–aquifer exchange using an empirical riverbed leakance parameter that is predefined or calibrated from observed head differences between the stream and aquifer. Here, we describe the numerical implementation of the analytical stream aquifer flow exchange (SAFE) formulation (Morel-Seytoux et al., 2018) within the finite-element-based Integrated Water Flow Model (IWFM). SAFE represents stream–aquifer exchange using physically based parameters and provides an alternative to commonly used first order exchange (FOE) formulations, such as the MODFLOW River Package (RIV). A key extension is the ability to quantify asymmetric stream–aquifer exchange arising from different groundwater heads on opposing sides of a stream, a capability not available in standard stream–aquifer interaction packages. Numerical experiments using hypothetical test cases and a large-scale regional application demonstrate that differences in conductance and connectivity parameterizations produce distinct spatial and temporal patterns of simulated exchange. Compared with FOE, the SAFE formulation produces smoother temporal transitions and reduced short-term variability in simulated exchange. These results demonstrate the importance of conceptual model formulation when interpreting simulated stream–aquifer exchange and provide a physically based alternative for large-scale integrated groundwater–surface water modeling.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 5","pages":"650-668"},"PeriodicalIF":2.6,"publicationDate":"2026-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.70098","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148763987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GroundwaterPub Date : 2026-09-13Epub Date: 2026-08-24DOI: 10.1111/gwat.70101
Paul Whincup
{"title":"Zamzam, the World's Most Sacred Groundwater Well: Mecca, Saudi Arabia","authors":"Paul Whincup","doi":"10.1111/gwat.70101","DOIUrl":"10.1111/gwat.70101","url":null,"abstract":"","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 5","pages":"697-701"},"PeriodicalIF":2.6,"publicationDate":"2026-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148815253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GroundwaterPub Date : 2026-07-10Epub Date: 2026-05-26DOI: 10.1111/gwat.70084
Upasana Pandey, Andrew J. Stumpf, Yu-Feng F. Lin
{"title":"Aquifer Thermal Energy Storage: Groundwater for Efficient Data Center Cooling in the United States","authors":"Upasana Pandey, Andrew J. Stumpf, Yu-Feng F. Lin","doi":"10.1111/gwat.70084","DOIUrl":"10.1111/gwat.70084","url":null,"abstract":"<p>Data centers are energy end users with the fastest growing need for electricity in the United States, mainly because of the rapid expansion of cloud computing and artificial intelligence (AI). A substantial portion of this electricity, between 10% and 40%, is used for cooling. As the number of data centers increases and the sector's energy demand continues to rise exponentially, there is an urgent need to explore the use of alternative energy systems that are more efficient and sustainable. This article explores aquifer thermal energy storage (ATES) as a technically feasible and currently underutilized solution for data center cooling in the United States. Previous case studies from Europe and assessments based in the United States are considered, and the potential of ATES for reducing electricity usage for data centers, which would reduce overall greenhouse gas emissions and support sustainable energy operations.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 4","pages":"394-404"},"PeriodicalIF":2.6,"publicationDate":"2026-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.70084","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148019599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GroundwaterPub Date : 2026-07-10Epub Date: 2026-05-05DOI: 10.1111/gwat.70079
Wondwosen M. Seyoum
{"title":"Satellite Remote Sensing for Water Management","authors":"Wondwosen M. Seyoum","doi":"10.1111/gwat.70079","DOIUrl":"https://doi.org/10.1111/gwat.70079","url":null,"abstract":"","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 4","pages":"389-390"},"PeriodicalIF":2.6,"publicationDate":"2026-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148532481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GroundwaterPub Date : 2026-07-10Epub Date: 2026-05-15DOI: 10.1111/gwat.70081
Konstantin Drach, Carsten Leven, Olaf A. Cirpka
{"title":"Discharge-Targeted Hydraulic Tomography to Quantify and Locate Aquifer Discharge","authors":"Konstantin Drach, Carsten Leven, Olaf A. Cirpka","doi":"10.1111/gwat.70081","DOIUrl":"10.1111/gwat.70081","url":null,"abstract":"<p>Quantifying and localizing groundwater discharge is inherently difficult. It requires knowledge about hydraulic conductivity and the hydraulic gradient on the scale of interest. Conventional hydraulic testing, such as pumping tests, may fail in the presence of heterogeneity and complex structural boundaries. While advanced 2D and 3D hydraulic tomography may resolve small-scale heterogeneity, it is typically limited to small spatial scales and requires costly field installations. We propose a simplified tomographic approach using a limited number of pumping and observation wells spatially distributed over a well profile in the order of 100 m transverse to the direction of ambient flow. To infer the spatially variable hydraulic-conductivity field from drawdown data with its uncertainty, we apply an iterative ensemble smoother. Subsequently, the posterior ensemble of hydraulic-conductivity fields is used to calculate total and specific discharge based on the observed ambient hydraulic heads in the same wells. We test our approach in a synthetic scenario mimicking a channel-like aquifer such as the quaternary fill in a small river valley. The results demonstrate that multiple spatially distributed pumping tests are suitable to quantify total discharge and its associated uncertainty. The approach is more reliable than a conventional one that estimates effective transmissivity from fitting analytical solutions to pumping-test data. The tomographic analysis additionally allows locating spatial patterns of specific discharge at a resolution similar to the spacing of the wells, which may be important when assessing and remediating contaminant plumes.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 4","pages":"466-482"},"PeriodicalIF":2.6,"publicationDate":"2026-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.70081","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147949956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GroundwaterPub Date : 2026-07-10Epub Date: 2026-06-02DOI: 10.1111/gwat.70083
Aaron Peche, Fritz Kalwa, Syed Mohaiminul Islam, Georg Houben, Thomas Graf, Sven Altfelder
{"title":"Leaky Sewers Hydraulically Disconnect from Groundwater: A Proof-of-Concept","authors":"Aaron Peche, Fritz Kalwa, Syed Mohaiminul Islam, Georg Houben, Thomas Graf, Sven Altfelder","doi":"10.1111/gwat.70083","DOIUrl":"10.1111/gwat.70083","url":null,"abstract":"<p>Leakage from aging sewer and stormwater pipes into the subsurface poses significant environmental risks and threatens the integrity of urban infrastructure, primarily through the degradation of groundwater quality and the alteration of urban water balances. While the presence of defects within pipe networks is well-documented, accurately quantifying volumetric exchange fluxes remains a challenge due to the complex, nonlinear interactions between the pipe, the surrounding variably saturated soil, and the fluctuating groundwater level. Current modeling approaches often overlook the threshold behaviors of these systems, leading to potential inaccuracies in leakage estimation. In this study, we show for the first time that leaky pipes can become hydraulically disconnected from the underlying groundwater, a phenomenon analogous to well-known river–groundwater interactions that include disconnection. In a sewer–groundwater context, hydraulic disconnection is restricted to point sources and is strongly influenced by colmation/clogging. Through numerical modeling of a hypothetical case study, we show that the leakage flux from the pipe (in absolute terms) initially increases with declining groundwater levels, until a critical depth below the leaky pipe is reached. After this point, the hydraulic communication from the groundwater to the leaky pipe stops and the leakage flux can be considered constant. In a sensitivity analysis, we demonstrate the impact of the individual hydraulic parameters of the leaky-pipe-groundwater system on the hydraulic disconnection. We further modify the properties of the aquifer material, resulting in a hydraulic disconnection depth of 0.89 m, 1.77 m and 4.00 m below pipe for sand, loamy sand and sandy loam aquifers, respectively. This insight has important implications for leakage modeling: once hydraulic disconnection occurs, the leakage flux becomes independent of groundwater dynamics. The present study provides a proof-of-concept for the mechanism by which leaky sewers hydraulically disconnect from groundwater.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 4","pages":"483-497"},"PeriodicalIF":2.6,"publicationDate":"2026-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.70083","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148145931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GroundwaterPub Date : 2026-07-10Epub Date: 2026-04-24DOI: 10.1111/gwat.70072
Paul E. Stackelberg, Katherine J. Knierim, Kenneth Belitz, Charles A. Cravotta III, R. Blaine McCleskey, Courtney D. Killian
{"title":"Predicting Groundwater Hydrochemical Facies in Three Dimensions with Random Forest Classification, USA","authors":"Paul E. Stackelberg, Katherine J. Knierim, Kenneth Belitz, Charles A. Cravotta III, R. Blaine McCleskey, Courtney D. Killian","doi":"10.1111/gwat.70072","DOIUrl":"10.1111/gwat.70072","url":null,"abstract":"<p>A random forest classification (RFC) model was developed to predict hydrochemical facies (HCFs) of groundwater in three dimensions across the conterminous United States (CONUS). Major-ion data from 152,673 sites were used to categorize groundwater into one of six HCFs (CaMg-HCO<sub>3</sub>, NaK-HCO<sub>3</sub>, CaMg-SO<sub>4</sub>, NaK-SO<sub>4</sub>, Cl, or Mixed). These six HCFs were used as targets for RFC modeling. Model features that represent relevant geochemical processes and/or physical conditions were derived from previously published data. Additional model features were specifically engineered to support this analysis: elevation of the bottom of a well relative to the base of drinking water (ERDW) and six flags that relate geologic units to HCFs. The most important model feature was ERDW. The model was used to map HCFs at a 1-km<sup>2</sup> resolution across CONUS and to depths of 400 m below the base of drinking water (which varies from 22 m to 2 km). Model predictions are consistent with expectations. CaMg-HCO<sub>3</sub> is predicted to occur near the water table in more humid settings, and areas underlain by carbonate or crystalline rocks. At depths below the base of drinking-water supplies, the model predicts a rapid transition from HCO<sub>3</sub> HCFs to Cl. Model predictions are accurate based on point data, and data averaged across hydrogeologic regions and with depth. Model predictions of HCFs could be used for multiple purposes, including the mapping of salinity and other groundwater characteristics.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 4","pages":"422-440"},"PeriodicalIF":2.6,"publicationDate":"2026-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.70072","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147792994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}