GroundwaterPub Date : 2025-01-24DOI: 10.1111/gwat.13465
Frédérik Croteau, Cécile Coulon, John Molson, Jean-Michel Lemieux
{"title":"Impact of Long Well Screens on Monitoring of the Freshwater-Saltwater Transition Zone","authors":"Frédérik Croteau, Cécile Coulon, John Molson, Jean-Michel Lemieux","doi":"10.1111/gwat.13465","DOIUrl":"10.1111/gwat.13465","url":null,"abstract":"<p>Deep monitoring wells with long screens crossing the transition zone between freshwater and saltwater are often used in coastal areas to characterize fresh groundwater resources and the depth of saline groundwater. However, past studies have demonstrated that long-screen wells can lead to biased observations of the transition zone, since vertical flow within the borehole can modify the shape and elevation of the transition zone in and around the borehole compared to undisturbed conditions without a well. Here, field observations and variable-density numerical flow simulations are used to evaluate, under natural flow conditions, how the installation of long-screen wells can provide time-varying biased observations of the freshwater-saltwater transition zone, and how various aquifer and well parameters affect the magnitude of these biases. Results show that long-screen wells can lead to a more dispersed interface, an upward displacement of the transition zone of between 5 and 10 m, and a salinity decrease in the saltwater portion of the well on the order of 10 to 15 g/L. The perturbations take up to 5 years to fully develop and stabilize. The degree of displacement depends on the screen diameter, screen length, aquifer anisotropy, and hydraulic conductivity, whereas the displacement is independent of the distance of the well from the coast. This analysis provides insight into which well and aquifer characteristics increase the risk of obtaining biased observations in long-screen wells, and provides orders of magnitude for these biases.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"63 2","pages":"192-204"},"PeriodicalIF":2.0,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.13465","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143034882","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}
{"title":"Dissolved Inorganic Carbon Evolution of Sediment Porewater in the Huixian Wetland, Southwest China","authors":"Jing Li, Xiaodong Pan, Huanxiong Chen, Congming Huang, Ruirui Cheng","doi":"10.1111/gwat.13466","DOIUrl":"10.1111/gwat.13466","url":null,"abstract":"<p>Wetlands, as crucial terrestrial carbon reservoirs, have recently suffered severe degradation due to intense human activities. Lacustrine sediments serve as vital indicators for understanding wetland environmental changes. In the current paper, porewater samples were extracted from lacustrine sediment in three boreholes with a depth of ~75 cm in the Huixian karst wetland, southwest China, to study the chemical and dissolved inorganic carbon (DIC) evolution under anthropogenic influence. Two boreholes are situated beneath the Mudong Lake, while the other one is in the degraded wetland area. The results show that porewater in the central region of Mudong Lake is natural HCO<sub>3</sub>–Ca type water and recharged by karst groundwater as evidenced by depleted <sup>2</sup>H -<sup>18</sup>O isotopes. Methanogenesis prevails in this area, suggested by positive δ<sup>13</sup>C values ranging from 4.29‰ to 7.05‰. However, shallow porewater at the western edge of Mudong Lake and porewater in the degraded wetland exhibit significantly higher concentrations of NO<sub>3</sub><sup>−</sup> and SO<sub>4</sub><sup>2−</sup>, resulting from the agricultural input and recharged groundwater influenced by oxidation of pyrite. These processes lead to a decrease in methane production and generate DIC through degradation of organic fertilizer and carbonate weathering by sulfuric acid, thereby significantly altering porewater δ<sup>13</sup>C values. Two types of DIC mixing processes were observed based on the increasing δ<sup>13</sup>C values with depth, which can be attributed to the unique karst groundwater subsystems. This work highlights the potential impact of human-induced porewater chemical variations on the fate of DIC, particularly in karst wetland environments.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"63 3","pages":"433-446"},"PeriodicalIF":2.0,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143018247","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 : 2025-01-16DOI: 10.1111/gwat.13459
Alden M. Provost, Kerry Bardot, Christian D. Langevin, James L. McCallum
{"title":"Accurate Simulation of Flow through Dipping Aquifers with MODFLOW 6 Using Enhanced Cell Connectivity","authors":"Alden M. Provost, Kerry Bardot, Christian D. Langevin, James L. McCallum","doi":"10.1111/gwat.13459","DOIUrl":"10.1111/gwat.13459","url":null,"abstract":"<p>In simulations of groundwater flow through dipping aquifers, layers of model cells are often “deformed” to follow the top and bottom elevations of the aquifers. When this approach is used in MODFLOW, adjacent cells within the same model layer are vertically offset from one another, and the standard conductance-based (two-point) formulation for flow between cells does not rigorously account for these offsets. The XT3D multi-point flow formulation in MODFLOW 6 is designed to account for geometric irregularities in the grid, including vertical offsets, and to provide accurate results for both isotropic and anisotropic groundwater flow. A recent study evaluated the performance of the standard formulation and XT3D using a simple, synthetic benchmark model of a steeply dipping aquifer. Although XT3D generally improved the accuracy of flow simulations relative to the standard formulation as expected, neither formulation produced accurate flows in cases that involved large vertical offsets. In this paper, we explain that the inability of XT3D to produce accurate flows in the steeply dipping aquifer benchmark was not due to an inherent limitation of the flow formulation, but rather to the limited cell connectivity inherent in the most commonly used discretization packages in MODFLOW 6. Furthermore, we demonstrate that XT3D is able to produce the expected accuracy when adequate cell connectivity is introduced using MODFLOW's unstructured grid type and the aquifer is discretized vertically using at least two model layers.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"63 3","pages":"399-408"},"PeriodicalIF":2.0,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.13459","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143018220","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 : 2025-01-06DOI: 10.1111/gwat.13463
Chandler Noyes, Jennifer C. McIntosh, Nicholas Dutka, Rebecca Tyne, Matthew B.J. Lindsay, Grant Ferguson
{"title":"Groundwater Ages in Intertill and Buried Valley Aquifers in Saskatchewan, Canada","authors":"Chandler Noyes, Jennifer C. McIntosh, Nicholas Dutka, Rebecca Tyne, Matthew B.J. Lindsay, Grant Ferguson","doi":"10.1111/gwat.13463","DOIUrl":"10.1111/gwat.13463","url":null,"abstract":"<p>Continental glaciations during the Pleistocene Epoch created complex systems of aquifers and aquitards across many northern regions of the Earth. The low hydraulic conductivities of glacial till aquitards suggest that limited recharge will reach the underlying aquifers, potentially preserving old groundwaters. Here, we characterize the recharge history in intertill and buried valley aquifers in Saskatchewan, Canada using <sup>14</sup>C, <sup>3</sup>H, <sup>4</sup>He δ<sup>2</sup>H, δ<sup>18</sup>O, and major ions. Intertill aquifers with depths of <30 m had corrected <sup>14</sup>C ages ranging from 0 to 15.5 ka. These aquifers also contained <sup>3</sup>H and/or elevated NO<sub>3</sub> in some locations, indicating that a component of modern recharge had mixed with older water. A single sample from the Judith River bedrock aquifer in the region had a corrected <sup>14</sup>C age of 10.2 ka and elevated NO<sub>3</sub>. Samples from buried valley aquifers with depths of 89 to 123 m contained older waters with ages >38 ka in some locations, indicating that recharge occurred before the last glacial advance over the region. While measuring tracers that cover a wide range of ages is necessary to understand these flow systems, δ<sup>2</sup>H and δ<sup>18</sup>O were less diagnostic because values of modern winter precipitation overlapped with groundwaters with a wide range of ages. The range of ages present in the intertill aquifers of the region indicates that these systems are currently being recharged, which indicates some development of groundwater resources is possible but also points to a need for groundwater protection measures.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"63 2","pages":"160-174"},"PeriodicalIF":2.0,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.13463","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142934218","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 : 2024-12-29DOI: 10.1111/gwat.13461
Weigang Su, Yujun Ma, Qiugui Wang
{"title":"Applying 224Ra and 223Ra to Trace Lateral Groundwater Discharge into Lake Qinghai, China","authors":"Weigang Su, Yujun Ma, Qiugui Wang","doi":"10.1111/gwat.13461","DOIUrl":"10.1111/gwat.13461","url":null,"abstract":"<p>Quantifying lacustrine groundwater discharge (LGD) is important for understanding the dynamics of lake ecosystems and their expansion. This study focuses on Lake Qinghai, employing radium isotope models to evaluate the contributions of both shallow and deep groundwater. The data indicate that the activity of <sup>223</sup>Ra and <sup>224</sup>Ra demonstrates a pronounced gradient, decreasing from the shoreline to the center of Lake Qinghai. Additionally, vertical stratification characteristics were observed. The spatial distribution of radium isotope activity suggests that there is discharge of both shallow and deep groundwater into the lake. Deep groundwater migrates slowly and its apparent age reflects the time elapsed since the water became enriched in Ra and was isolated from the source, in the study system this age is estimated to be 10.1 d. In contrast, shallow groundwater displayed varied apparent ages in different regions: 7.9 d in the north, 13.1 d in the south, and 7.4 d in the southeastern area of the lake. The LGDs of shallow groundwater discharge in the north, south, and southeast areas of Lake Qinghai were estimated by <sup>224</sup>Ra as 1.89 × 10<sup>6</sup> to 2.69 × 10<sup>6</sup> m<sup>3</sup>/d, 3.25 × 10<sup>6</sup> to 3.99 × 10<sup>6</sup> m<sup>3</sup>/d, and 4.51 × 10<sup>6</sup> to 6.33 × 10<sup>6</sup> m<sup>3</sup>/d, respectively. For deep groundwater, the LGD was 0.16 × 10<sup>6</sup> to 0.29 × 10<sup>6</sup> m<sup>3</sup>/d. Annually, the total LGD fluxes of shallow and deep groundwater are 27.86 × 10<sup>8</sup> to 37.59 × 10<sup>8</sup> m<sup>3</sup>/year and 0.58 × 10<sup>8</sup> to 1.06 × 10<sup>8</sup> m<sup>3</sup>/year, respectively. This study is the first to evaluate shallow and deep groundwater discharge around the lake. Understanding these discharge dynamics is essential for developing effective management strategies to preserve lake environments.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"63 3","pages":"422-432"},"PeriodicalIF":2.0,"publicationDate":"2024-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142908013","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 : 2024-12-27DOI: 10.1111/gwat.13462
Mohammadali Geranmehr, Domenico Bau, Alex S. Mayer, Weijiang Yu
{"title":"A Reduced Order Model for Sea Water Intrusion Simulation Using Proper Orthogonal Decomposition","authors":"Mohammadali Geranmehr, Domenico Bau, Alex S. Mayer, Weijiang Yu","doi":"10.1111/gwat.13462","DOIUrl":"10.1111/gwat.13462","url":null,"abstract":"<p>Sea water intrusion (SWI) simulators are essential tools to assist the sustainable management of coastal aquifers. These simulators require the solution of coupled variable-density partial differential equations (PDEs), which reproduce the processes of groundwater flow and dissolved salt transport. The solution of these PDEs is typically addressed numerically with the use of density-dependent flow simulators, which are computationally intensive in most practical applications. To this end, model surrogates are generally developed as substitutes for full-scale aquifer models to trade off accuracy in exchange for computational efficiency. Surrogates represent an attractive option to support groundwater management situations in which fast simulators are required to evaluate large sets of alternative pumping strategies. Reduced-order models, a sub-category of surrogate models, are based on the original model equations and may provide quite accurate results at a small fraction of computational cost. In this study, a variable-density flow reduced-order model based on proper orthogonal decomposition (POD) and utilizing a fully coupled flow and solute-transport model is implemented with a finite-difference (FD) approach for simulating SWI in coastal aquifers. The accuracy and computational efficiency of the FD-POD approach for both homogeneous and—more realistic—heterogeneous systems are investigated using test cases based on the classic Henry's problem (Henry 1964). The findings demonstrate that the combined FD-POD approach is effective in terms of both accuracy and computational gain and can accommodate the output of the most popular variable-density flow models, such as those from USGS's MODFLOW family.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"63 2","pages":"205-219"},"PeriodicalIF":2.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.13462","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142901430","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 : 2024-12-20DOI: 10.1111/gwat.13458
Zachary D. Tomlinson, Kato T. Dee, Megan E. Elwood Madden, Andrew S. Elwood Madden
{"title":"Applying the Quadrant Method for Pumping-Trace Metal Correlations in Variable Time, Low-Data Systems","authors":"Zachary D. Tomlinson, Kato T. Dee, Megan E. Elwood Madden, Andrew S. Elwood Madden","doi":"10.1111/gwat.13458","DOIUrl":"10.1111/gwat.13458","url":null,"abstract":"<p>Due to increasing global demand for fresh water, it is increasingly necessary to understand how aquifer pumping affects groundwater chemistry. However, comprehensive predictive relationships between pumping and groundwater quality have yet to be developed, as the available data, which are often collected over inconsistent time intervals, are poorly suited for long-term historical correlation studies. For example, we needed an adequate statistical method to better understand relationships between pumping rate and water quality in the City of Norman (OK, USA). Here we used the interval-scaled change in mean pumping rate combined with the Quadrant method to examine correlations between pumping rates and changes in trace metal concentrations. We found that correlations vary across the study area and are likely dependent on a variety of factors specific to each well. Comparing the Quadrant method to the commonly used Kendall's tau correlation, which requires different assumptions about aquifer behavior, the methods produced similar correlations when sample sizes were large and the time interval between samples was relatively short. Sample sizes were then artificially restricted to determine correlation reproducibility. Despite being less reproducible overall, the Quadrant method was more reproducible when there were large time intervals between samples and very small sample sizes (<i>n</i> ~ 4), but not as reproducible as significant (p ≤ 0.1) Kendall's tau correlations. Therefore, the Quadrant method may be useful for further investigating the effects of pumping in cases where Kendall's tau does not produce significant correlations.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"63 2","pages":"256-264"},"PeriodicalIF":2.0,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.13458","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142866791","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 : 2024-12-19DOI: 10.1111/gwat.13457
Warren W. Wood, Ward E. Sanford, John A. Cherry, Warren T. Wood
{"title":"Global Groundwater Carbon Mass Flux and the Myth of Atmospheric Weathering","authors":"Warren W. Wood, Ward E. Sanford, John A. Cherry, Warren T. Wood","doi":"10.1111/gwat.13457","DOIUrl":"10.1111/gwat.13457","url":null,"abstract":"<p>Our recent steady-state mass-balance modeling suggests that most global carbonic-acid weathering of silicate rocks occurs in the vadose zone of aquifer systems not on the surface by atmospheric CO<sub>2</sub>. That is, the weathering solute flux is nearly equal to the total global continental riverine carbon flux, signifying little atmospheric weathering by carbonic acid. This finding challenges previous carbon models that utilize silicate weathering as a control of atmospheric CO<sub>2</sub> levels. A robust analysis utilizing global estimates of groundwater carbon concentration generated by a geospatial machine learning algorithm was coupled with recharge flux in a geographic information system environment to yield a total global groundwater carbon flux of between 0.87 and 0.96 Pg C/year to the surface environment. On discharging to the surface, the carbon is speciated between 0.01 and 0.11 Pg C/year as CaCO<sub>3</sub>; 0.35 and 0.38 Pg C/year as CO<sub>2</sub> gas; and 0.49 and 0.51 Pg C/year as dissolved HCO<sub>3</sub><sup>−</sup>. This total weathering carbon flux was calculated for direct ocean discharge (0.030 Pg C/year); endorheic basins (0.046 Pg C/year); cold-wet exorheic basins (0.058 Pg C/year); warm-dry exorheic basins (0.072 Pg C/year); cold-dry exorheic basins (0.115 Pg C/year); and warm-wet exorheic basins (0.448 Pg C/year).</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"63 1","pages":"14-24"},"PeriodicalIF":2.0,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11697531/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142857284","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 : 2024-12-19DOI: 10.1111/gwat.13455
Alexis Koulidis, Tessel M. Grubben, Martin L. van der Schans, Martin Bloemendal, Philip J. Vardon
{"title":"The Impact of Bridging Additives on Wellbore Strengthening in Shallow Unconsolidated Formations","authors":"Alexis Koulidis, Tessel M. Grubben, Martin L. van der Schans, Martin Bloemendal, Philip J. Vardon","doi":"10.1111/gwat.13455","DOIUrl":"10.1111/gwat.13455","url":null,"abstract":"<p>Drilling wells in unconsolidated formations is commonly undertaken to extract drinking water and other applications, such as aquifer thermal energy storage (ATES). To increase the efficiency of an ATES system, the drilling campaigns are targeting greater depths and enlarging the wellbore diameter in the production section to enhance the flow rates. In these cases, wells are more susceptible to collapse. Drilling fluids for shallow formations often have little strengthening properties and, due to single-string well design, come into contact with both the aquifer and the overburden. Drilling fluids and additives are experimentally investigated to be used to improve wellbore stability in conditions simulating field conditions in unconsolidated aquifers with a hydraulic conductivity of around 10 m/d. The impact on wellbore stability is evaluated using a new experimental setup in which the filtration rate is measured, followed by the use of a fall cone penetrometer augmented with an accelerometer to directly test the wellbore strengthening, and imaging with a scanning electron microscope (SEM) to investigate the (micro)structure of the filter cakes produced. Twelve drilling fluids are investigated with different concentrations of bentonite, polyanionic cellulose (PAC), Xanthan Gum, calcium carbonate (CaCO<sub>3</sub>), and aluminum chloride hexahydrate ([Al(H<sub>2</sub>O)<sub>6</sub>]Cl<sub>3</sub>). The filtration results indicate that calcium carbonate, average <i>d</i><sub><i>p</i></sub> <20 <i>μ</i>m, provides pore throat bridging and filter cake formation after approximately 2 min, compared to almost instantaneous discharge when using conventional drilling fluids. The drilling fluid containing 2% [Al(H<sub>2</sub>O)<sub>6</sub>]Cl<sub>3</sub> forms a thick (4 mm) yet permeable filter cake, resulting in high filtration losses. The fall cone results show a decrease of cone penetration depth up to 20.78%, and a 40.27% increase in deceleration time while penetrating the sample with CaCO<sub>3</sub> compared with conventional drilling fluid containing bentonite and PAC, indicating a significant strengthening effect. The drilling fluids that contain CaCO<sub>3</sub>, therefore, show high promise for field implementation.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"63 2","pages":"231-247"},"PeriodicalIF":2.0,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.13455","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142866802","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}