• Giant Sequoia Trees

    Sequoia & Kings Canyon

    National Parks California

Karst Hydrology

Cave stream with layers of erosion clearly visible
What makes karst landscapes distinctive is that they can develop underground channels that allow for the rapid movement of water through rock.
NPS Photo
 
Caves are just a small part of a greater geological phenomena known as karst. Named for a region of Slovenia, karst describes areas of the earth's surface that have caves, springs, sinkholes, disappearing streams and other unusual landforms. These features develop when mildly acidic groundwater acts on soluble rock, such as limestone marble or gypsum, to erode away the stone.

Karst hydrology is the study of the movement and properties of groundwater flowing through karst areas. It is the actions of this water that makes caves, sinkholes and other karst features. Karst hydrology has become an important area of research in recent years because groundwater in this setting behaves very differently from groundwater in a normal geologic region. Usually groundwater moves through the earth very slowly through tiny pores, spaces and fractures in rock. These small spaces may act as filters that clean and purify groundwater. In a karst system, groundwater flows rapidly through open conduits and passages in the rock. Groundwater is not filtered or naturally purified in karst systems.

Because of the rapid flow and lack of filtering in karst water systems, these areas are very susceptible to pollution. Millions of people and many unique species of animals depend on clean water in karst areas for drinking and for aquatic homes. In the Eastern United States where karst has developed across thousands of square miles, ground water pollution is a big concern. Accidents, such as trains or trucks spilling toxic chemicals, may result in ground water pollution across a large area, ruining wells and destroying wildlife habitat. In the Sierra Nevada karst areas are limited in their extent. But maintaining good water quality in these areas is still very important. Karst waters in Sequoia and Kings Canyon support unique animals and are a part of watersheds that supply thousands of people with water for drinking and irrigation.

In karst areas, hydrologists strive to understand where the water at springs originates and where the water flowing into sinkholes is headed. Delineating these karst watersheds helps scientists know where to look for problems is there is a toxic spill. This work also defines what habitat is available for karst dwelling animals and may shed light on the nature and extent of undiscovered cave systems.

The hydrologists' most important tool in defining a karst watershed is dye tracing. In such an experiment non-toxic, super-concentrated dyes are added to a stream where it disappears underground. Special dye receptors made of activated charcoal are placed in all of the springs and caves of an area where a test is being conducted. Dye absorbed into the receptors confirms a positive test, and a hydrologic connection between the stream and the spring is confirmed. Karst hydrology defined by these studies may be very complicated and involve water traveling dozens of miles beneath numerous surface watersheds. Often many springs and water sink points may be shown to be connected through a series of dye traces.

Karst hydrology research in Sequoia and Kings Canyon has taken place at various times during the past 20 years. This work has been done by the park and also by members of the Cave Research Foundation. These studies have confirmed the source of the streams in Crystal, Hurricane Crawl, Lilburn, and some Mineral King caves. In the future the park hopes to expand its program of dye tracing to areas with karst springs but no caves and to other caves with active streams. This work will help us prepare for any toxic spills on park roads or from park buildings, and will help us to define the parks' habitat for cave adapted animals.

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