Karst hydrogeology of the Chalk and implications for groundwater protection

The Chalk is an unusual karst aquifer with limited cave development, but extensive networks of smaller solutional conduits and fissures enabling rapid groundwater flow. Small-scale karst features (stream sinks, dolines, dissolution pipes, and springs) are common, with hundreds of stream sinks recorded. Tracer velocities from 27 connections between stream sinks and springs have median and mean velocities of 4700 and 4600 m.d.−1. Tests to abstraction boreholes also demonstrate very rapid velocities of 1000s m.d.−1. Natural gradient tests from observation boreholes have rapid velocities of 100s m.d.−1. There is strong geological control on karst with dissolution focused on stratigraphical inception horizons. Surface karst features are concentrated near the Palaeogene boundary, or where thin superficial cover occurs, but rapid groundwater flow is also common in other areas. The Chalk has higher storage and contaminant attenuation than classical karst, but recharge, storage and flow are influenced by karst. Point recharge through stream sinks, dolines, losing rivers, vertical solutional fissures, and soakaways enables rapid unsaturated zone flow. Saturated zone networks of solutional fissures and conduits create vulnerability to subsurface activities, and enable long distance transport of point source and diffuse pollutants, which may be derived from outside modelled catchment areas and source protection zones.

Development and implementation of virtual field teaching resources: two karst geomorphology modules and three virtual capstone pathways

During the summer of 2020, many geology field camps were canceled due to the COVID-19 pandemic, including the karst geomorphology field course I was scheduled to co-teach through Western Kentucky University. When the National Association of Geoscience Teachers (NAGT), in collaboration with the International Association for Geoscience Diversity (IAGD), began the project of supporting working groups to create online field experience teaching materials, this presented an opportunity. This paper describes the development of two activities derived from that field camp curriculum that are now freely available as peer-reviewed exemplary teaching activities on the Science Education Resource Center (SERC) Online Field Experiences repository under “Karst hydrogeology: a virtual field introduction using © Google Earth and Geographic Information Systems (GIS)” and “Karst hydrogeology: a virtual field experience using © Google Earth, GIS, and TAK [Topographic Analysis Kit].” Each product includes a student handout, an instructor workflow reference, a grading rubric, and NAGT-established learning objectives. The introductory activity is the more basic of the two, is expected to take about an 8 h workday to teach, and walks students through all the steps, as well as providing global examples of karst landscapes that can be virtually explored. The other activity, “Karst hydrogeology and geomorphology”, assumes student familiarity with © Google Earth, GIS, and karst drainage systems and is expected to take about twice as long as the introductory activity to teach. To make these learning opportunities financially accessible, all software required for the activities is open source, and alternative workflows for the introductory module are provided so that the entire exercise can be completed using a mobile device. Addressing this need for virtual capstone options during the pandemic, and providing a virtual alternative for years to come, these karst activities, along with a subset of other SERC activities, were assembled into three learning tracks, each one providing learning hours equivalent to a traditional field camp, that have been added to the course offerings at the University of Cincinnati Department of Geology. In addition to providing online capstone activities in the time of a pandemic, these learning materials provide alternative experiences to traditional field camps that are inclusive for all geoscience students.

From Field to Phone: A Karst Camp Chronicle

During the summer of 2020, many geology field camps were cancelled due to the COVID-19 pandemic, including the Karst Geomorphology field course I was scheduled to co-teach through Western Kentucky University. When the National Association of Geoscience Teachers (NAGT) in collaboration with the International Association for Geoscience Diversity (IAGD) began the project of supporting working groups to create online field experience teaching material, I saw an opportunity. From my field camp syllabus, I created two activities that are now freely available as peer-reviewed Exemplary Teaching Activities on the Science Education Resource Center (SERC) Online Field Experiences repository: Karst Hydrogeology: A virtual field introduction using © Google Earth and GIS and Karst Hydrogeology and Geomorphology: A virtual field experience using © Google Earth, GIS, and TAK [Topographic Analysis Kit]. Each product includes a student handout, an instructor workflow reference, a grading, and NAGT-established learning objectives. The introductory activity is the more basic of the two, is expected to take about one 8-hour day to teach, and walks students through all the steps, as well as providing global examples of karst landscapes to virtually explore. The other activity, Karst Hydrogeology and Geomorphology, assumes student familiarity with © Google Earth, GIS, and karst drainage systems, and is expected to take about twice as long as the introductory activity to teach. To make these learning opportunities financially accessible, all software required for the activities is open-source and alternative workflows for the introductory module are provided so that the entire exercise can be completed using a smartphone. In addition to providing online capstone activities in the time of a pandemic, these activities provide alternative learning experiences to traditional field camps that are inclusive for all geoscience students. In my home department of the University of Cincinnati, I had been contacted by students needing to find capstone experiences when their field camps were cancelled. Responding to this need and providing a virtual alternative for years to come, I reviewed all SERC activities that had been generated during the NAGT/IAGD joint effort. I selected a subset of those to assemble into three learning tracks, each one providing learning hours equivalent to a traditional field camp, that have been added to the course offerings at the University of Cincinnati Department of Geology.

Review: Advances in the methodology and application of tracing in karst aquifers

Tracer methods have been widely used in many fields of environmental and natural sciences, and also in human health sciences. In particular, tracers are used in the study of karst hydrogeology, typically focusing on phenomena such as sinkholes, sinking rivers and large karst springs. It is known that tracers have been used since antiquity. The aim of tracer tests has been to investigate underground flow paths, transport processes and water–rock interactions, and to get an insight into the functioning of a karst aquifer. In karst hydrogeology, tracer methods are the most important investigation tools beside conventional hydrological methods. In early times, tracer methods were applied only to investigate underground flow-paths. Later they were also used to elucidate transport processes associated with water flow, and today they are often the basis, together with detailed hydrological information, of groundwater protection investigations and aquifer modelling. Many substances (spores, microspheres, bacteriophages, salt tracers, fluorescent dyes, radioactive substances) have been investigated for their properties and potential usage in environmental investigations, in particular the often unknown and inaccessible underground systems of karst areas. A great number of analytical techniques is available. This includes instrumentation for laboratory applications and direct online, on-site or in-situ field measurements. Modern instruments have a high capability for data acquisition, storage and transmission in short intervals, as a basis for quantitative evaluation and modelling. This enables research on the hydrological and hydrochemical dynamics of aquifers and their response to different natural or anthropogenic impacts.

Hydraulic Behavior of Karst Aquifers

The objective of this Special Issue, “Hydraulic Behavior of Karst Aquifers”, is to focus on recent advances in karst hydrogeology in different areas of the world, focusing on topics dealing with the peculiar characteristics of karst aquifers. In particular, thirteen peer-reviewed articles were collected, focusing on hydraulic aspects and their relationship with geological features, geochemical and bacteriological aspects, tunneling and engineering mining inrush, and forecasting water resources and drought occurrences. Overall, these contributions describe several aspects of karst aquifers and are of great value for water resource management and protection.