Review of Laboratory Scale Models of Karst Aquifers: Approaches, Similitude, and Requirements

Abstract

This review focuses on investigations of groundwater flow and solute transport in karst aquifers through laboratory scale models (LSMs). In particular, LSMs have been used to generate new data under different hydraulic and contaminant transport conditions, testing of new approaches for site characterization, and providing new insights into flow and transport processes through complex karst aquifers. Due to the increasing need for LSMs to investigate a wide range of issues, associated with flow and solute migration karst aquifers this review attempts to classify, and introduce a framework for constructing a karst aquifer physical model that is more representative of field conditions. The LSMs are categorized into four groups: sand box, rock block, pipe/fracture network, and pipe‐matrix coupling. These groups are compared and their advantages and disadvantages highlighted. The capabilities of such models have been extensively improved by new developments in experimental methods and measurement devices. Newer technologies such as 3D printing, computed tomography scanning, X‐rays, nuclear magnetic resonance, novel geophysical techniques, and use of nanomaterials allow for greater flexibilities in conducting experiments. In order for LSMs to be representative of karst aquifers, a few requirements are introduced: (1) the ability to simulate heterogeneous distributions of karst hydraulic parameters, (2) establish Darcian and non‐Darcian flow regimes and exchange between the matrix and conduits, (3) placement of adequate sampling points and intervals, and (4) achieving some degree of geometric, kinematic, and dynamic similitude to represent field conditions.

Karst water resources in a changing world: Review of solute transport modelling approaches

“…For instance, the partition coefficient (K d ) and mass transfer coefficient (i.e., first-order mass transfer coefficient) could not be generalized (e.g., Stockmann et al, 2017;Swami et al, 2018) because their values are extremely varied (often by order of magnitudes) at the field-scale measurements depending both on the matrix hydraulic properties (e.g., surface area, matrix porosity, permeability) and on the fracture/conduit characteristics (Howroyd & Novakowski, 2021;Lehmann et al, 2022;Maloszewski & Zuber, 1993;Zhou et al, 2007). Similarly, the values for reactive transport parameters could also be misleading particularly when they are scaled up or extrapolated, because of the oversimplification of the multifaceted processes that are varied both by chemical heterogeneities in the matrix and local/global groundwater chemistry (e.g., Howroyd & Novakowski, 2021;Jiang et al, 2023;Katz et al,1998;Kaufmann et al, 2014;Mohammadi et al, 2021;Maqueda et al, 2023, among many others). For this reason, a realistic definition of the reactive transport parameters is strictly limited by the well-defined karstic sites or site-specific applications (i.e., single-well push-pull test) (e.g., Hillebrand et al, 2012aHillebrand et al, , 2012bHillebrand et al, , 2015Priebe et al, 2022;Schiperski et al, 2016;Tran et al, 2020Tran et al, , 2021.…”

From the Mental to the Conceptual Model: The Challenge of Teaching Hydrogeology in the Field

“…When teaching hydrogeology in the field, lecturers often show block diagrams or sketches representing a conceptual model for a hydrogeological system, but how these conceptual models have been elaborated is often not described in detail. To overcome this issue, the development of students' spatial reasoning skills, for example, through two‐dimensional (2D) or three‐dimensional (3D) digital and numerical models (Greca and Moreira 2000; Bredehoeft 2005) or with the inclusion of physical models for classroom (prior‐to‐field) teaching—“making the invisible visible”—(Rodhe 2012; Cardiff and Heinle 2019; Shanafield et al 2019; Mohammadi et al 2021), have been considered (Gleeson and Paszkowski 2014). Spatial, that is, spatial visualization skills, and temporal, that is, knowledge of the characteristic times of processes, reasoning abilities contribute substantially to the development of plausible conceptual models of systems and processes such as those found in groundwater (Dickerson et al 2007).…”

Study on the Equivalent Permeability Coefficient of Karst Conduit with Single Conduit and Multigroup Fissures

“…erefore, this indoor model test only considers the combined karst geological model of two groups of mutually perpendicular fissures and one karst conduit. e indoor test model can be divided into four parts: water supply system, in which water from nearby lakes is pumped by submersible pumps and enters the water supply tank; monitoring system, which is a row of observation hole preset above the conduit, and the observation hole is connected with the conduit and the fissures nearby, and the water level of the conduit in the flow field can be directly measured by a steel tape; water storage system, in which the water discharged through the conduit enters the overflow tank and then flows into the water tank, and the water discharge will be recorded by reading the water level and bottom area of the water tank; rock mass model, including rock block, karst conduit and two groups of fissures which are perpendicular to each other, simulates rock block by the module bonded with acrylic board (i.e., without considering seepage inside rock block), simulates karst fissure by space between modules (two surfaces of crack are parallel to each other and the distance remains constant), and simulates karst conduit by presetting round pipes in the module (the pipe is straight and its diameter remains unchanged) [12][13][14][15]. e pipe is separated by vertical fissures, and water in the fissure and water in the pipe can be exchanged with each other in the process of groundwater flowing [16].…”