Interactions of diffuse and focused allogenic recharge in an eogenetic karst aquifer (Florida, USA)

Abstract

The karstic upper Floridan aquifer in northcentral Florida (USA) is recharged by both diffuse and allogenic recharge. To understand how recharged water moves within the aquifer, water levels and specific conductivities were monitored and slug tests were conducted in wells installed in the aquifer surrounding the Santa Fe River Sink and Rise. Results indicate that diffuse recharge does not mix rapidly within the aquifer but instead flows horizontally. Stratification may be aided by the high matrix porosity of the eogenetic karst aquifer. Purging wells for sample collection perturbed conductivity for several days, reflecting mixing of the stratified water and rendering collection of representative samples difficult. Interpretive numerical simulations suggest that diffuse recharge impacts the intrusion of allogenic water from the conduit by increasing hydraulic head in the surrounding aquifer and thereby reducing influx to the aquifer from the conduit. In turn, the increase of head within the conduits affects flow paths of diffuse recharge by moving newly recharged water vertically as the water table rises and falls. This movement may result in a broad vertical zone of dissolution at the water table above the conduit system, with thinner and more focused water-table dissolution at greater distance from the conduit.

Formation of phreatic caves in an eogenetic karst aquifer by CO2 enrichment at lower water tables and subsequent flooding by sea level rise

“…The cave water also remained either supersaturated or very close to saturation regardless of the undersaturation of flood waters in the river. Although large volumes of river water did not intrude the Devil's Cave system during Tropical Storm Fay, flooding decreased SpC and increased temperature in the River Rise system during this same event (Langston et al ., ), indicating the flood was capable of forcing water into the Floridan Aquifer at locations that have discrete swallets. The lack of dilute, calcite‐undersaturated flood water flowing to the Devil's Cave system stems from the lack of upstream swallets that can divert river water into the cave.…”

Influence of partial confinement and Holocene river formation on groundwater flow and dissolution in the Florida carbonate platform

“…It stores water in the aquifer matrix and attenuates discharge peaks as flood pulses propagate from Worthington Springs to the River Rise (Figure ), shown clearly during flooding resulting from Tropical Storm Fay (Figure ). The decrease in peak discharge and extended hydrograph recession curves indicate that floodwater was stored as rapid increases in conduit heads drove water from the conduit into the aquifer (Moore et al ., ; Bailly‐Comte et al ., 2011; Langston et al ., ). Long tails on the recession hydrographs demonstrate this water was later released from storage as conduit heads decreased after the flood (Moore et al ., ).…”

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

“…Based on previous studies published for the region we have assumed that the conduits remain fully saturated throughout the study period (e.g. Langston et al, 2012). ParFlow does not contain algorithms for turbulent conduit flow, therefore conduits were represented as high hydraulic conductivity zones in this study.…”

“…Table 2 summarizes the spatial input data used to develop the baseline ParFlow.CLM model for the SFRB. Conduit locations were taken from Meyer et al (2008) and each conduit was assumed to be 10 m in height and to occur between depths of 5-15 m below mean sea level based on previous field investigations (Langston et al, 2012). Based on previous studies published for the region we have assumed that the conduits remain fully saturated throughout the study period (e.g.…”