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Wind Cave National Park Hydrology

For millions of years rain and snow have fallen on the prairie and slowly seeped into the cave. In the past 100 years, however, human development has brought about a change to this natural water cycle. This change, which could be damaging to the cave, has prompted park researchers to study the flow of water from the prairie to the lowest depths of Wind Cave.

It may seem like a difficult task to track water droplets as they move through the soil and into the cracks and passageways of the cave. But, there is an effective technique that can be used. It is called dye tracing and it is the focus of cave research at Wind Cave National Park.

Dye-tracing is very simple in theory. A non-toxic, colored dye mixed with water is poured onto a selected spot on the surface. The colored water then travels through the cracks and pores of the limestone, where it is captured in chosen collection sites in the cave. The results of the dye-trace help researchers understand how developments over the cave are affecting the water that enters it.

A Wind Cave dye-trace was initiated on July 29, 1996. Two different colored dyes were mixed with enough water to simulate a storm with one inch of rainfall. The dyes were poured into two separate locations about 400 yards apart. The results were quite surprising: both dyes ended up in the same place! The dye-trace showed that water does not always seep straight downward, but may travel horizontally for distances and then drop into the cave.

The area around the visitor center has changed dramatically in the past 100 years. Thousands of visitors use the area each day. Buildings, sewer lines, a parking lot, and cars occupy space directly above the cave. These "new inhabitants" may be causing damage to the fragile ecosystem below. Of all the developments, the parking lot seems to be the greatest concern.

Water that would naturally be absorbed into the ground is funneled off the parking lot into four specific spots. That causes water to enter the cave at unnatural rates and locations. Not only are the amounts and locations of water changed, the channeled water can carry oil, gas, antifreeze and other pollutants from the parking lot into the cave. Some of these have already shown up in trace amounts at water collecting sites in the cave.

To solve some of these problems, park managers redesigned the parking lot, creating one that will eliminate most damage to the cave. Our goal is to have a more natural path for water to follow into the cave, a path reminiscent of the past, a path that created the beauty that is Wind Cave.

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