GIS Uncovers Hidden River Polluters

Survey Data Overlay Provides Evidence

Groundwater resources, often overlooked because they lie unseen beneath the surface of the earth, are playing an ever more crucial role in a world with increasing industrial development, increasing population and increasing demands on agricultural production. Protecting and managing groundwater resources is critical not only to public health but also to sustainable economic development.

Most of the freshwater resources in the United States are groundwater. Approximately one quarter of the groundwater is located in regions. One of the world's best known karst areas is in south central Kentucky, USA, home of Mammoth Cave. With almost 350 miles of passageways mapped to date, it is the longest cave in the world.

Nearby lies Hidden River Cave, located directly beneath the town of Horse Cave. Hidden River Cave contains an underground river that once was the source of drinking water for the town. At the beginning of this century, the river was harnessed to supply the town with hydroelectricity. The cave was also commercialized and shown to tourists from 1912 through 1943.

Groundwater pollution from domestic and industrial sewage was one of the factors that led to the cave's closing in 1943. For 50 years Hidden River Cave was little more than an open sewer, its huge entrance emitting a sickening odor that drove tourists away and often made life very uncomfortable for the residents. Although it was known that wastes were entering the cave, there was no real understanding of the relationship between cave passages and the town.

Researchers working under Dr. James Quinlan began dye-tracing underground streams in the area in the 1970s. Dye-tracing involves dumping dye in locations where it is likely to be carried some distance—often a great distance—by the groundwater. It is then detected by dye detectors that have been positioned in springs, underground streams or other likely places. Over the years enough dye-trace data was collected to permit Quinlan and Joe Ray to create a map of the approximate underground flow routes for the area around Mammoth Cave, including the underground river (Hidden River) beneath Horse Cave.

But there was still not enough information to form a precise picture of the relationship between the cave passages and the town above. Researchers began surveying the cave in 1989, mapping over seven miles, but even with the survey data they lacked tools to depict the relationship between the underground passages and the surface terrain.

The Cave Research Foundation, currently leading the survey effort in the cave, applied for a software grant from the ESRI Conservation Program. The software—ArcView GIS with the 3D Analyst and Spatial Analyst extensions—provided the tools to do the job. Integrating cave survey data with USGS surface data, the GIS software clearly revealed the spatial relationship between the underground passages and the town, revealing how local surface waste disposal sites fed directly into the cave.

Today, Hidden River Cave is operated by the American Cave Conservation Association, which relocated their national headquarters to Horse Cave with the goal of restoring Hidden River Cave and establishing a museum and educational center at the site. Thousands of tourist visitors and school children annually tour Hidden River Cave and the American Cave Museum at the cave's entrance. The cave, which has been called "the greatest cave restoration success story in the United States" is now open year-round to visitors. Guided tours lead visitors to views of the underground river and a turn-of-the-century hydro-electric generating system which once supplied the town above with water and electric power.

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