Springflow Hydrographs: Eogenetic vs. Telogenetic Karst
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Abstract
Matrix permeability in the range of 10−11 to 10−14 m2 characterizes eogenetic karst, where limestones have not been deeply buried. In contrast, limestones of postburial, telogenetic karst have matrix permeabilities on the order of 10−15 to 10−20 m2. Is this difference in matrix permeability paralleled by a difference in the behavior of springs draining eogenetic and telogenetic karst? Log Q/Q min flow duration curves from 11 eogenetic‐karst springs in Florida and 12 telogenetic‐karst springs in Missouri, Kentucky, and Switzerland, plot in different fields because of the disparate slopes of the curves. The substantially lower flow variability in eogenetic‐karst springs, which results in the steeper slopes of their flow duration curves, also makes for a strong contrast in patterns (e.g., “flashiness”) between the eogenetic‐karst and telogenetic‐karst spring hydrographs. With respect to both spring hydrographs and the flow duration curves derived from them, the eogenetic‐karst springs of Florida are more like basalt springs of Idaho than the telogenetic‐karst springs of the study. From time‐series analyses on discharge records for 31 springs and published time‐series results for 28 additional sites spanning 11 countries, we conclude that (1) the ratio of maximum to mean (Q max/Q mean) discharge is less in springs of eogenetic karst than springs of telogenetic karst; (2) aquifer inertia (system memory) is larger in eogenetic karst; (3) eogenetic‐karst aquifers take longer to respond to input signals; and (4) high‐frequency events affect discharge less in eogenetic karst. All four of these results are consistent with the hypothesis that accessible storage is larger in eogenetic‐karst aquifers than in telogenetic‐karst aquifers.
