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Karst Groundwater

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Published on: Mar. 2, 2000

Last revision: Nov. 4, 2010

day of poorly treated industrial sewage into the regional karst groundwater system. Contaminants sinking through this stream polluted rural wells and springs in a 60 square mile area.

Runoff from pasture lands can also degrade water quality via losing streams. Strips of ungrazed vegetation along stream channels, and especially along the normally dry losing stream channels, remove many contaminants from storm water. Even a vegetative strip as narrow as 50 feet wide along each bank of a losing stream channel is valuable in protecting groundwater quality.

Suburban and urban developments increase the quantity and decrease the quality of storm runoff water that reaches losing streams. When a storm hits, the vast majority of the contaminants are concentrated in the first quarter to half inch of storm runoff water. This "first flush" storm water runoff, often similar in quality to raw city sewage, enters our karst groundwater supplies through sinkholes or losing streams.

Developers often construct basins to detain storm water and reduce flash flooding in urban and suburban areas. However, most of these basins do not provide treatment to improve the quality of the detained water, and in some cases these detention basins have been located on top of losing stream segments. Improved storm water management approaches for urban and suburban activities are needed in Missouri's karst areas. Karst groundwater quality cannot be protected without ensuring good quality recharge water.

Karst groundwater systems provide habitat for many fascinating animals. Except for caves with large bat populations, most of the food for cave animals is washed in through discrete recharge zones. As a result, cave fauna is commonly concentrated around the points where these discrete recharge zones connect to caves.

A fascinating characteristic of karst groundwater movement is the great speed with which much of the water moves. Karst groundwater travel rates in Missouri are often in the range of a mile per day. In non-karst areas, groundwater travel rates are commonly only a few feet per year.

The longest distance groundwater trace in the United States was from a losing stream segment of the Eleven Point River to Big Spring. Big Spring is 39.5 miles away and in the Current River basin. The dye introduced in the losing stream was first detected at Big Spring 16 days later.

Not all groundwater moves at the same speed. As a result, a contaminant may reach some springs or wells within a few hours or days of the time it entered the groundwater system, while the contaminant from the same source may not reach other wells for weeks or months. Travel times also depend upon characteristics of the contaminants. The net result is that cleaning up groundwater, including karst groundwater, is routinely slow, difficult, expensive and seldom totally successful. As with most natural systems, damage is easy, fixing is difficult and prevention is best.

Another unique feature of karst groundwater systems is that water entering the subsurface at a single point may sometimes discharge from multiple springs and wells. The discharge points are sometimes in different stream or river basins and may be separated from one another by a number of miles. Such complex flow systems help explain the relatively large ranges for some aquatic cave species. The range of Ozark cavefish, for example extends from Springfield southwestward into northwest Arkansas and northeast Oklahoma

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