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Abstract:
In karst aquifers, water moves from the recharge area (sinkhole plains and swallets) to the discharge area (springs), traveling kilometers through the groundwater system in a period of hems to days. Transit rimes through karst aquifers are a function of the conduit geometry and connectedness, intensity and duration of the recharge event, and antecedent soil moisture. Often many of these factors are unknown or difficult to quantify. Therefore, predicting the response of a karst basin to recharge is difficult. Numerous researchers have attempted to understand the response of a karst basin, but a good understanding of whether the response is dependent on local features or regional effects is currently lacking. From April 1994 to May 1995, flood pulse hydrographs from a karst aquifer with well-developed and well-documented conduits (Devil's Icebox cave system) were obtained from a gaging station near the spring of the karst basin. Data were also collected from within the conduit system in an attempt to determine whether flow was locally controlled by constrictions in the conduits. Based on an application of Bernoulli's equation, analyses of the changes in kinetic head and potential head over time indicated local control during storm events. The observed sediment patterns and water level variations also support localized flow control during storm events. A numerical model of the constrictions was rested and reproduced the responses observed at the spring during initial periods of storm events. The model illustrated that the constricted flow was very sensitive to recharge. It also illustrated the transition from local control due to constriction to regional controls due to the aquifer matrix. (C) 1998 Elsevier Science B.V