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Degradation of aquifer water quality can lead to detrimental effects on species that rely on the aquifer for habitat. In the case of the Edwards Aquifer, various threatened and endangered species rely on that habitat for survival. For example, the endangered San Marcos Gambusia (Gambusia georgei) is recorded as extremely sensitive to habitat alteration; changes in water turbidity or temperature in particular. Managing the changes in water quality is critical to the stewardship of these threatened and endangered species.
Edwards is a karst aquifer, with a great deal of limestone which is a highly soluble rock. A karst aquifer has many fissures and conduits, resulting in rapid groundwater flow and greater interconnectivity between surface and groundwater. For Edwards, this means a relatively fast recharge time; the aquifer is very sensitive to precipitation. Changes in precipitation show the rapid response of the aquifer's water level. The figures shown to the right display precipitation and groundwater level changes over the years; note the rapid response time of the aquifer to the changes in precipitation.
Precipitation - Edwards Aquifer
Karst Aquifers in the US
US Karst Aquifers [Map: USGS]
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. Because of their importance as drinking water sources and the unique habitat they provide for many threatened and endangered species in the US, karst formations must be protected now and in the future.
