Visualization of conduit‐matrix conductivity differences in a karst aquifer using time‐lapse electrical resistivity

Abstract

In the karstic upper Floridan aquifer, surface water flows into conduits of the groundwater system and may exchange with water in the aquifer matrix. This exchange has been hypothesized to occur based on differences in discharge at the Santa Fe River Sink‐Rise system, north central Florida, but has yet to be visualized using any geophysical techniques. Using electrical resistivity tomography, we conducted a time‐lapse study at two locations with mapped conduits connecting the Santa Fe River Sink to the Santa Fe River Rise to study changes of electrical conductivity during times of varying discharge over a six‐week period. Our results show conductivity differences between matrix, conduit changes in resistivity occurring through time at the locations of mapped karst conduits, and changes in electrical conductivity during rainfall infiltration. These observations provide insight into time scales and matrix conduit conductivity differences, illustrating how surface water flow recharged to conduits may flow in a groundwater system in a karst aquifer.

Time‐lapse electrical resistivity imaging of solute transport in a karst conduit

“…In a karst aquifer, Meyerhoff et al . (, ) recently used time‐lapse ERI to monitor the movement of relatively low‐conductivity surface water through a mapped conduit in response to rainfall. Although they did not verify the interpreted resistivity signal with an in situ monitoring well, their study suggests that time‐lapse ERI is a tool with great potential in karst systems.…”

Characteristics of Point Recharge in Karst Aquifers

“…In Europe, more than 30% of the land surface is made up of karst exposures with more than half the drinking water supply derived from karst aquifers in some countries [13]. Karst aquifers are poorly understood due to the spatial and temporal complexity of flow patterns caused by widely varying porosity and flow regimes [11].…”

“…For example, 25% of drinking water supplies are sourced from a geological setting covering approximately 10% of the earth's land surface [9][10][11], and comprise some 40% of the groundwater of the United States [12]. In Europe, more than 30% of the land surface is made up of karst exposures with more than half the drinking water supply derived from karst aquifers in some countries [13].…”

Insights on geologic and vegetative controls over hydrologic behavior of a large complex basin – Global Sensitivity Analysis of an integrated parallel hydrologic model

“…The region that marks the transition from the confined to the unconfined conditions is characterized by the presence of numerous sinkholes, sinking streams, siphons, springs and other karst features which have the potential to rapidly recharge the UFAS (Meyerhoff et al, 2012Upchurch, 2007). During baseflow conditions the upper Santa Fe River is captured in its entirety by the Santa Fe River Sink in the transition region.…”