GroundwaterPub Date : 2025-12-26DOI: 10.1111/gwat.70044
Madeline Gotkowitz, David Hart
{"title":"Aquitards in Groundwater Systems: Groundwater Special Issue","authors":"Madeline Gotkowitz, David Hart","doi":"10.1111/gwat.70044","DOIUrl":"10.1111/gwat.70044","url":null,"abstract":"<p>Low-permeability geologic layers within groundwater systems, commonly referred to as aquitards or confining layers, are important controls of groundwater flow. Aquitards generally restrict groundwater flow and, importantly, can limit contaminant migration to adjacent aquifers. However, they are rarely spatially uniform or isotropic, varying in thickness and lithologic composition. At regional scales, most aquitards contain some type of heterogeneity, such as fractures or erosional windows, that affect groundwater flow and contaminant transport. Many groundwater investigations focus on aquifers, while the physical and chemical characteristics of aquitards, and their role in flow systems, may be over-simplified. Aquitards add complexity to almost all aspects of flow and transport in groundwater systems.</p><p>This <i>Groundwater</i> special issue, Aquitards in Groundwater Systems, has its roots in a recent Geological Society of America conference. A hydrogeology session included a presentation that referenced “aquifers, aquitards and aquitardifers,” which induced giggles from some audience members and affirming head nods from others. The diversity of listener reactions suggested an opportunity to pursue a compilation of topical papers that span the current breadth and depth of aquitard studies.</p><p>In this issue, Runkel and Meyer take on the hydrogeologic lexicon with formal introduction of “aquitardifer.” The term encompasses the anisotropy they document within low-conductivity formations. Such anisotropy can lead to restriction of flow in one direction while providing transmissivity in other directions. This explains production wells that are successfully completed in formations generally characterized as confining units. By explicitly identifying significant anisotropy in low-permeability sedimentary units, Runkel and Meyer advance the field of aquitard science.</p><p>Aquitard science is not consistently integrated within hydrogeologic curriculum, and students may not be prepared to recognize flow systems where aquitards play a significant role. Meyer and others discuss teaching activities (lab exercises and field measurements) that help students develop understanding and intuition of the role aquitards play in flow systems.</p><p>Methods to investigate and characterize aquifer heterogeneity are plentiful in the scientific literature but are not yet fully explored within the realm of aquitards. Van Leer and others model hydraulic response to pumping in an idealized, layered system of aquitards and aquifers. By illustrating key principles in pumping test design, they inform our understanding of drawdown in a heterogeneous aquitard.</p><p>The mechanical properties of aquitards can also present challenges. Hinton and others look at the increasing risk of landslides as the geochemistry of a marine clay aquitard is altered, from the initial mix of glacial and seawater pore fluids, by modern-day recharge. The change in pore fluid reduces the stre","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 1","pages":"4-5"},"PeriodicalIF":2.0,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ngwa.onlinelibrary.wiley.com/doi/epdf/10.1111/gwat.70044","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145835544","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 : 2025-12-15DOI: 10.1111/gwat.70042
Jessica R. Meyer, Stephanie Tassier-Surine, Bradley Cramer
{"title":"Teaching Aquitard Concepts With Field-Based High-Resolution Head Profile Learning Activities","authors":"Jessica R. Meyer, Stephanie Tassier-Surine, Bradley Cramer","doi":"10.1111/gwat.70042","DOIUrl":"10.1111/gwat.70042","url":null,"abstract":"<p>Aquitards play critical roles in a variety of hydrogeologic processes. Despite their importance, coverage of aquitards in introductory hydrogeology textbooks is generally limited. This paper provides examples of classroom and field activities designed with an aquitard focus for instructors wishing to supplement textbook content. These activities emphasize high-resolution head profiles. Examining head profiles prompts students to think about how aquitards influence head with depth and conversely how these plots can be used to delineate and characterize aquitards. During a classroom activity, students explore the connection between changes in vertical gradient and changes in hydraulic conductivity by sketching conceptual head profiles based on given boundary conditions and several aquifer/aquitard scenarios. In a companion field exercise, students measure high-resolution head profiles using CMT multilevel systems at an outdoor learning laboratory. Students compare the high-resolution head profiles to lower resolution profiles they obtain from clusters of conventional wells. The field exercise provides students with a tactile experience that can help build intuition for vertical head changes, practice interpreting aquitards from head profiles, and an example of how lower resolution head profiles may create uncertainty in aquitard delineation and vertical gradient estimates. A paleosol at the site forms a prominent aquitard providing a unique basis for discussions about the geology of aquitards and characteristics influencing aquitard integrity. Regardless of the approach used, incorporating more aquitard content into hydrogeology courses at all levels will be beneficial for future hydrogeologists tackling a range of issues from sustainable water supplies to waste disposal.</p>","PeriodicalId":12866,"journal":{"name":"Groundwater","volume":"64 1","pages":"21-29"},"PeriodicalIF":2.0,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12857529/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145764625","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}
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