Karst and Pseudokarst Aquifers in the Continental United States [Figure: Houston Advanced Research Center utilizing data from the National Atlas Principal Aquifers dataset].
The Karst Aquifer portal highlights the Edwards
aquifers in the CSWGCIN and SWIN regions. The portal features information and data, as well as an interactive mapping application, on groundwater and surface water conditions, precipitation, and threatened and endangered species in the Edwards, Ozarks and Roswell aquifers. Click on the highlighted aquifers on the map above to go to their associated mapping applications.
An Introduction to Karst
Karst is a unique land formation characterized by springs, caves, and sinkholes formed when carbon dioxide enriched water dissolves limestone and dolomite rock. Over 20% of the US land surface has underlying karst and because of the large fissures created by the dissolution of limestone and dolomite, large amounts of fresh water are trapped in these formations. Groundwater trapped in karst formations (aquifers) provides about 25% of the country's groundwater drinking supply. These large fissures assure that groundwater is quickly recharged; however, this also means karst aquifers are sensitive to contamination. The National Caves Association page on Cave Science
describes the basic physical and chemical processes behind the formation of karst features such as aquifers and caves.
Karst formations such as caves, sinkholes, springs and seeps provide habitat for hundreds of sensitive species, including many threatened and endangered species. Cave habitats support an estimated 1353 troglobitic (cave-dwelling) species in the United States, composed of 425 aquatic species and 928 terrestrial species (Elliot, 2000). Tables
from Elliot lists all the extinct, threatened and endangered, candidate, and species petitioned for listing that are associated with cave habitats in the United States.
Threats to Karst Habitat and Biota
Elliot lists the major threats to karst habitats. These are hydrological threats, which includes alteration of groundwater and surface water flows. Land development is another threat due to destruction, disturbance, or isolation of caves and cave species. Both nutrient loss and nutrient enrichment are threats to cave species because they alter cave biota. Exotic species such as fire ants and giant reed have been found in cave habitats and near karst springs. Chemical pollution in both aquatic and terrestrial cave and karst habitats can have devastating effects on karst species and threaten groundwater, even at small concentrations. Other threats include killing, disturbing and over-collection of species.
Elliot, W.R. (2000). Conservation of the North American Cave and Karst Biota. Chap. 34,
Wilkens H., D.C. Culver, and W.F. Humphreys (eds.),
. Ecosystems of the World, 30. Elsevier, Amsterdam. xiv + 791 pp.