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Originally published in U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011. Credit U.S. Geological Survey Department of Interior/USGS

Abstract

Karst ground-water basin divides are generally depicted as two-dimensional lines on maps, but they are better considered as three-dimensional surfaces within the subsurface. Dye traces are necessary to map out these surfaces and to locate conduits inaccessible to cave surveyors, and are indispensable for understanding the geometry of the complex networks of flow paths through the aquifer. A key reason why the Mammoth Cave System is the world's longest known cave is that its passages extend over several major ground-water basins. The divides between these basins define the drainage system geometry and precise location of them is critical for understanding and protecting the cave and its remarkable aquatic ecosystem. In 1999 we initiated a long-term program of dye tracing within the Mammoth Cave System to more precisely locate the divides and to understand their increasingly apparent complexities. In this paper we report on results of some of the more interesting dye injections of the program. Although the Mammoth Cave Karst Aquifer is perhaps the best understood conduit flow network in the world (with over 700 traces), we have found that much more work is needed to provide the level of understanding necessary for protection and conservation. The first reason is a matter of scale and resolution: with the current distribution of traces that define the ground-water basins, many regional basin divides are only approximately defined. In areas where this condition exists in combination with potential threats to ground-water quality (primarily urban and transportation areas) additional tracing is needed to know the flow paths of individual recharge points. A second reason for additional traces is to increase our understanding of the plumbing of active conduits through the karst aquifer. While this type of dye tracing is logistically demanding, requiring visits to in-cave dye recovery locations, it is adding a new level of detail to our understanding of the nature of the karst aquifer.

Disciplines

Earth Sciences | Geography | Geology | Geomorphology | Hydrology

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