Conduit Properties and Karstification in the Unconfined Floridan Aquifer

Abstract

Exchange of water between conduits and matrix is an important control on regional chemical compositions, karstification, and quality of ground water resources in karst aquifers. A sinking stream (Santa Fe River Sink) and its resurgence (River Rise) in the unconfined portion of the Floridan Aquifer provide the opportunity to monitor conduit inflow and outflow. The use of temperature as a tracer allows determination of residence times and velocities through the conduit system. Based on temperature records from two high water events, flow is reasonably represented as pipe flow with a cross-sectional area of 380 m2, although this model may be complicated by losses of water from the conduit system at higher discharge rates. Over the course of the study year, the River Rise discharged a total of 1.9 x 10(7) m3 more water than entered the River Sink, reflecting net contribution of ground water from the matrix into the conduit system. However, as River Sink discharge rates peaked following three rainfall events during the study period, the conduit system lost water, presumably into the matrix. Surface water in high flow events is typically undersaturated with respect to calcite and thus may lead to dissolution, depending on its residence time in the matrix. A calculation of local denudation is larger than other regional estimates, perhaps reflecting return of water to conduits before calcite equilibrium is reached. The exchange of matrix and conduit water is an important variable in karst hydrology that should be considered in management of these water resources.

Quantitative hermeneutics: Counting forestructures on a path from W.M. Davis to the concept of multiple-permeability karst aquifers

“…In the following few years, there was an outpouring of new papers on the exchange of water between conduits and matrix, the resultant enlargement of the conduits, the role of diffuse recharge in supplying the springs, the role of the high matrix permeability in shaping the spring hydrographs, the morphology of the caves that do not appear to be conduits, the occurrence of caves in levels, and the origin of the conduits in a time frame of Pleistocene eustasy (Screaton et al, 2004;Martin et al, 2006;Florea, 2006;Florea & Vacher, 2006Ritorto et al, 2009;Moore et al, 2009Moore et al, , 2010Gulley et al, 2011Gulley et al, , 2013Gulley et al, , 2014a. In all these papers, the guiding thought was that the Floridan aquifer represents a karst with high matrix permeability due to its intergranular porosity as opposed to closely spaced fissures .…”

Characterization and conceptualization of a relict Karst aquifer (Bilecik, Turkey)

“…For example, recharge may occur as either allogenic or autogenic in concentrated or diffuse forms (Jakucs 1959;Schuster & white 1971;Ternan 1972;Smart & Hobbs 1986;Hess & white 1988;Dreiss 1989;Martin & Dean 1999;Lee & Krothe 2001;Martin & Screaton 2001;Martin & Dean 2001;white 2003;Screaton et al 2004); Storage is also a property of the vadose zone as well as the phreatic zone (Mangin 1973;Kiraly & Morel 1976;Kiraly 2002;Dörfliger et al 2009), and flow may have a character of concentrated, dispersed, or a combination of those end members (white & Schmidt 1966;white 1969;Schuster & white 1971;quinlan et al 1996;Halihan et al 1998;worthington 1999;Screaton et al 2004;Abigail et al 2012). The complex structure of the karst aquifer makes direct determination of physical parameters related to these properties almost impossible.…”

Trends in Water Quality within the Broward County Portion of the Biscayne Aquifer

“…The Biscayne aquifer contains small-scale horizontal, lithostratigraphically concentrated, conduit development and features leading to high matrix conductivity. If contaminants from the surface are found solely within conduits the contaminant plume will be obvious fairly quickly; the outflow of this contaminated groundwater to surface water will be great in size but short-lived (Screaton, 2004). Water flow is often faster through conduits because they are composed of younger rocks that are not recrystalized carbonates.…”

“…The size of the cone within the different levels of the aquifer is based on the pumping rate and hydraulic characteristics of the aquifer itself. The high permeability of the karst aquifer allows a significant quantity of water flow through the unconfined aquifer media of the carbonate limestone that constitutes the Biscayne Aquifer (Ginn, 2004). In the shallow subsurface of the aquifer the cones of depression, created by in-use potable wells, respond rapidly to precipitation events .…”

“…Within the conduits, during low flow conditions such as found during the dry season, the conduits will drain water from the surrounding matrix (Bailly-Comte, 2010). During high flow conditions such as those found during the rainy season, may cause the larger conduits to reverse water flow from the conduits back into the adjacent aquifer matrix (Screaton, 2004). The groundwater recharge for the Biscayne Aquifer is mainly fed by precipitation received during the wet season (Pathak, 2010).…”