Identification of a hydrodynamic threshold in karst rocks from the Biscayne Aquifer, south Florida, USA

DiFrenna, Vincent J.; Price, René M.; Savabi, M. R.

doi:10.1007/s10040-007-0219-4

Cited by 15 publications

(16 citation statements)

References 30 publications

(37 reference statements)

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“…This enabled the determination of the pore size affected by the vacuum using the following equations as suggested by DiFrenna et al . [] which investigated a similar limestone from Key Largo, Florida. First, the change of pressure in the vacuum chamber (Δp) was calculated from the equation:

Δ p = Δ h p g

where Δh is the change in head, ρ is the density of water (1000 kg m 3 ), and g is the acceleration due to gravity (9.8 m s −2 ).…”

Section: Methodsmentioning

confidence: 99%

Estimating porosity and solid dielectric permittivity in the Miami Limestone using high‐frequency ground penetrating radar (GPR) measurements at the laboratory scale

Mount

Comas

2014

Water Resources Research

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Subsurface water flow in South Florida is largely controlled by the heterogeneous nature of the karst limestone in the Biscayne aquifer and its upper formation, the Miami Limestone. These heterogeneities are amplified by dissolution structures that induce changes in the aquifer's material and physical properties (i.e., porosity and dielectric permittivity) and create preferential flow paths. Understanding such patterns are critical for the development of realistic groundwater flow models, particularly in the Everglades, where restoration of hydrological conditions is intended. In this work, we used noninvasive ground penetrating radar (GPR) to estimate the spatial variability in porosity and the dielectric permittivity of the solid phase of the limestone at centimeter-scale resolution to evaluate the potential for field-based GPR studies. A laboratory setup that included high-frequency GPR measurements under completely unsaturated and saturated conditions was used to estimate changes in electromagnetic wave velocity through Miami Limestone samples. The Complex Refractive Index Model was used to derive estimates of porosity and dielectric permittivity of the solid phase of the limestone. Porosity estimates of the samples ranged between 45.2 and 66.0% and showed good correspondence with estimates of porosity using analytical and digital image techniques. Solid dielectric permittivity values ranged between 7.0 and 13.0. This study shows the ability of GPR to image the spatial variability of porosity and dielectric permittivity in the Miami Limestone and shows potential for expanding these results to larger scales and other karst aquifers.

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Δ p = Δ h p g

where Δh is the change in head, ρ is the density of water (1000 kg m 3 ), and g is the acceleration due to gravity (9.8 m s −2 ).…”

Section: Methodsmentioning

confidence: 99%

Estimating porosity and solid dielectric permittivity in the Miami Limestone using high‐frequency ground penetrating radar (GPR) measurements at the laboratory scale

Mount

Comas

2014

Water Resources Research

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“…From the formation factor as calculated by Tucker (2013), the porosity of the Miami oolite used in modeling is equal to approximately 33%, well within the bounds of previous estimates (Robinson, 1967;DiFrenna et al, 2008). Underestimations of the measured salinity at a well by the ERT-estimated value indicate a location where bedrock porosity is lower than this average, while overestimations indicate locations of higher bedrock porosity.…”

Section: Effects Of Bedrock Porosity On Ert-estimation Of Groundwatersupporting

confidence: 79%

“…Beginning on Big Pine Key and trending to the southwest, the Miami Limestone outcrops over the underlying Key Largo Limestone and contacts are separated by subaerial exposures . While both formations are moderately to highly porous (average porosity of 20 to 40%) (Robinson, 1967;DiFrenna et al, 2008), the Key Largo Limestone is more permeable than the Miami Limestone as a result of the greater development of secondary porosity . Longer periods of meteoric diagenesis of the underlying Key Largo Limestone are responsible for the increase in secondary porosity and interconnected pore spaces (Vacher et al, 1992).…”

Section: Study Areamentioning

confidence: 99%

The Effect of Disturbance and Freshwater Availability on Lower Florida Keys’ Coastal Forest Dynamics

Ogurcak¹

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th century has been attributed to a combination of sea level rise and hurricane storm surge impacts, but the interactions between these two disturbances leading to forest decline are not well understood. The goal of my research was to assess their effects over a period spanning more than two decades, and to examine the relationships between these press and pulse disturbances and freshwater availability in pine rockland, hardwood hammock, and supratidal scrub communities. Impacts and recovery from two storm surges, Hurricanes Georges (1998) and Wilma (2005), were assessed with satellite-derived vegetation indices and multiple change detection techniques. Impacts were greater at lower elevations, and in hardwood hammock, spectral signatures indicative of plant stress and productivity returned to predisturbance levels within a few years. In pine rockland, impacts were predominately related to Hurricane Wilma, however, a similar return to pre-disturbance conditions was absent, suggesting that trajectories of disturbance recovery differed between the two communities. Long-term monitoring of forest composition, structure, and groundwater salinity showed that compositional shifts in the low shrub stratum were associated with ix salinization of the freshwater resource attributable to sea level rise. Throughout the course of twelve months of climate and groundwater monitoring (2011)(2012), groundwater salinity generally decreased in response to large precipitation events.Modeling of geophysical data indicated that groundwater salinity was an important predictor of community type. Isotopic analysis of δ 18 O in plant stem water and foliar δ 13 C was used to determine temporal and spatial patterns in water use and plant stress in two community dominants, slash pine, Pinus elliottii var. densa, and buttonwood, Conocarpus erectus. Both species relied heavily on groundwater, and plant stress was related to increasing groundwater salinity. The results of this work suggest that the interaction of press and pulse disturbances drive changes in community composition by causing mortality of salt-sensitive species and altering the freshwater resource.x forests that require freshwater inhabit a unique position on low-elevation limestone islands as glycophyte-dominated forests located in close proximity to saline water.Coastal forests in the greater Caribbean basin are also subject to periodic disturbance from hurricanes and tropical storms, but which typically are not stand-replacing events (Brokaw and Walker, 1991;Yih et al., 1991;Bellingham et al., 1992). Collectively, these forests are high in species diversity , 2006). These conditions would favor a combination of disturbance, 2 drought, and salinity tolerant species, as groundwater salinity increases (Guha and Panday, 2012) and coastal forests are exposed more frequently to major storms, with shrinking recovery periods between such events (Lugo, 2000). Additionally, the interaction of press and pulse events will increase the likelihood of surface inundation by salt w...

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“…Using glass spheres, Schneebeli [1955] found that flow became turbulent when Re ranged from 5 to 60. Within limestone rocks from the Florida Keys, DiFrenna et al [2008] found non‐Darcian flow with effective porosity equal to about 33% and hydraulic conductivity equal to about 10 m d −1 . When flow transitions to turbulent, some of the energy that drives the flow is lost to movement of water in unsteady eddies, and specific discharge no longer increases as rapidly as the head gradient increases.…”

Section: Introductionmentioning

confidence: 94%

Effects of turbulence on hydraulic heads and parameter sensitivities in preferential groundwater flow layers

Shoemaker

Cunningham

Kuniansky

et al. 2008

Water Resources Research

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[1] A conduit flow process (CFP) for the Modular Finite Difference Ground-Water Flow model, MODFLOW-2005, has been created by the U.S. Geological Survey. An application of the CFP on a carbonate aquifer in southern Florida is described; this application examines (1) the potential for turbulent groundwater flow and (2) the effects of turbulent flow on hydraulic heads and parameter sensitivities. Turbulent flow components were spatially extensive in preferential groundwater flow layers, with horizontal hydraulic conductivities of about 5,000,000 m d À1 , mean void diameters equal to about 3.5 cm, groundwater temperature equal to about 25°C, and critical Reynolds numbers less than or equal to 400. Turbulence either increased or decreased simulated heads from their laminar elevations. Specifically, head differences from laminar elevations ranged from about À18 to +27 cm and were explained by the magnitude of net flow to the finite difference model cell. Turbulence also affected the sensitivities of model parameters. Specifically, the composite-scaled sensitivities of horizontal hydraulic conductivities decreased by as much as 70% when turbulence was essentially removed. These hydraulic head and sensitivity differences due to turbulent groundwater flow highlight potential errors in models based on the equivalent porous media assumption, which assumes laminar flow in uniformly distributed void spaces.

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Identification of a hydrodynamic threshold in karst rocks from the Biscayne Aquifer, south Florida, USA

Cited by 15 publications

References 30 publications

Estimating porosity and solid dielectric permittivity in the Miami Limestone using high‐frequency ground penetrating radar (GPR) measurements at the laboratory scale

Estimating porosity and solid dielectric permittivity in the Miami Limestone using high‐frequency ground penetrating radar (GPR) measurements at the laboratory scale

The Effect of Disturbance and Freshwater Availability on Lower Florida Keys’ Coastal Forest Dynamics

Effects of turbulence on hydraulic heads and parameter sensitivities in preferential groundwater flow layers

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