The unsaturated zone is a critical component of karstic groundwater systems and is shown to provide substantial storage capacities. Understanding the spatial patterns and controls on flow path activation is often a challenge. Previous research focused on remotely sensed data or inferential analyses to quantify these patterns. Here, we use two cave systems—one in Arizona, USA and a second in Kentucky, USA—to show the value of the cave survey and inventory data in the direct observation of speleogenesis and unsaturated zone processes. Using geospatial statistical analyses, we show that passage size varies with distance from some faults, indicating that these faults play a major role in transporting fluid into the limestone and creating increased permeability in the form of cave passages. Additionally, the close relationship between water, calcite resources and geology provide clear evidence for the activation of unsaturated zone flow paths through these cave systems. While both cave systems represent a large area of greatly increased permeability, only isolated sections of the caves show evidence of this active flow. In both cases, modern vadose zone flow occurs proximal to faults and contacts with overlying insoluble lithology. These results suggest that an expanded use of cave survey and inventory data may provide a greater insight into unsaturated zone processes.
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This research was funded by Grand Canyon National Park. This research was conducted under Cooperative Ecosystem Studies Units National Network Cooperative Agreement #P18AC01331 and Grand Canyon National Park Scientific Research and Collecting Permit #GRCA-2021-SCI-0014.
The data used in this study can be found here: (irma.nps.gov, accessed on 10 January 2022) and here: (kgs.uky.edu/kgsweb/main.asp, accessed on 10 January 2022). Grand Canyon National Park data was accessed through our research permit.
Published in Geosciences, v. 12, issue 2, 47. © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).