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Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

Did you know?

That convective transport is the component of movement of heat or mass induced by thermal gradients in ground water [22]. see also advection.?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for floridan (Keyword) returned 41 results for the whole karstbase:
Showing 16 to 30 of 41
Temperature as a natural tracer of short residence times for groundwater in karst aquifers, 1999, Martin J. B. , Dean R. W.
Chemistry of karst waters is controlled by reactions with aquifer rocks, the extent of mixing between water sources, and variations in the composition of recharged waterThe extent of reactions and mixing may be determined uniquely if compositions of both recharged and discharged water are known, such as where sinking streams are linked to resurgent springs, and if residence time in the subsurface can be measuredSuch a linked system occurs along the Santa Fe River in north-central Florida, where the river flows underground for approximately 52 km as it crosses from confined to unconfined portions of the Floridan AquiferTemporal variations in temperature can be correlated between the river sink, the river rise, and Sweetwater Lake, a karst window approximately midway between the sink and riseDelays in the arrival time of temperature maxima and minima from the sink to Sweetwater Lake and from Sweetwater Lake to the Rise reflect the residence time of the river water in the subsurfaceResidence time correlates with the river stage and ranges from approximately 12 hours to more than four days at high and low stage, respectively between the river sink and SweetwaterLake, and from about six hours to nearly two days at high and low stage, respectively, between Sweetwater Lake and the river riseThese short residence times reflect minimum flow rates of between 13 and 9 km/day, indicating conduit flowKnowing the residence time at any stage allows sampling of water as it enters the aquifer, and then again as it dischargesChanges in the chemistry of water as it passes through the subsurface should reflect chemical reactions, mixing, or both

Uncalculated impacts of unsustainable aquifer yield including evidence of subsurface interbasin flow, 2000, Bacchus St,
Unsustainable withdrawals from regional aquifers have resulted in adverse impacts considerable distances from the point locations of supply wells. In one area of the southeastern (SE) Coastal Plain, conservative estimates for repair/replacement of some residential wells damaged or destroyed by unsustainable yield from the Floridan aquifer system exceeded $4 million. However, a comprehensive assessment of damage/economic loss to private property and public resources due to unsustainable yield from that regional karat aquifer has not been made. Uncalculated direct costs to home-owners from damage attributed to those withdrawals are associated with destruction of homes from increased sinkhole formation, devalued waterfront property, and removal of diseased and dead trees. Examples of other uncalculated economic burdens resulting from unsustainable aquifer yield in the SE Coastal Plain include: (1) irreversible damage to the aquifer matrix and concomitant increased potential for groundwater contamination, (2) large-scale wildfires with subsequent degradation of air quality, debilitation of transportation corridors, and destruction of timber, wildlife habitat and property, and (3) destruction of 'protected' natural areas. This paper provides a general background of the regional Floridan aquifer system's karst characteristics, examples of known impacts resulting from ground water mining in the SE Coastal Plain, and examples of additional damage that may be related to unsustainable yield from the Upper Floridan aquifer. Costs of these impacts have not been calculated and are not reflected in the price users pay for ground water. Evidence suggests that the classic watershed management approach must be revised in areas with mined regional karst aquifers to include impacts of induced recharge from the surficial aquifer, and subsurface interbasin flow. Likewise, associated impacts to surface water and interrelated systems must be calculated The true cost of groundwater mining to this and future generations should be determined using a multidisciplinary approach

Timescales for nitrate contamination of spring waters, northern Florida, USA, 2001, Katz B. G. , Bohlke J. K. , Hornsby H. D. ,
Residence times of groundwater, discharging from springs in the middle Suwannee River Basin, were estimated using chlorofluorocarbons (CFCs), tritium ((3) H), and tritium/helium-3 (H-3/He-3) age-dating methods to assess the chronology of nitrate contamination of spring waters in northern Florida. During base-flow conditions for the Suwannee River in 1997-1999, 17 water samples were collected from 12 first, second, and third magnitude springs discharging groundwater from the Upper Floridan aquifer. Extending age-dating techniques, using transient tracers to spring waters in complex karst systems, required an assessment of several models [piston-flow (PFM), exponential mixing (EMM), and binary-mixing (BMM)] to account for different distributions of groundwater age. Multi-tracer analyses of four springs yielded generally concordant PFM ages of around 20 2 years from CFC- 12, CFC- 113, H-3, and He-3. with evidence of partial CFC- 11 degradation. The EMM gave a reasonable fit to CFC- 113, CFC- 12. and H-3 data, but did not reproduce the observed He-3 concentrations or H-3/He-3 ratios, nor did a combination PFM-EMM. The BMM could reproduce most of the multi-tracer data set only if both endmembers had H-3 concentrations not much different front modern values. CFC analyses of 14 additional springs yielded apparent PFM ages from about 10 to 20 years from CFC- 113, with evidence of partial CFC- 11 degradation and variable CFC-12 contamination. While it is not conclusive, with respect to the age distribution within each spring, the data indicate that the average residence times were in the order of 10-20 years and were roughly proportional to spring magnitude. Applying similar models to recharge and discharge of nitrate based on historical nitrogen loading data yielded contrasting trends for Suwanee County and Lafayette County. In Suwance County, spring nitrate trends and nitrogen isotope data were consistent with a peak in fertilizer input in the 1970s and a relatively high overall ratio of artificial fertilizer/manure whereas in Lafayette County, spring nitrate trends and nitrogen isotope data were consistent with a more monotonic increase in fertilizer input and relatively low overall ratio of artificial fertilizer/manure. The combined results of this study indicate that the nitrate concentrations of springs in the Suwannee River basin have responded to increased nitrogen loads from various sources in the watersheds over the last few decades, however, the responses have been subdued and delayed because the average residence time of groundwater discharging from springs are in the order of decades. (C) 2001 Published by Elsevier Science B.V

Exchange of water between conduits and matrix in the Floridan aquifer, 2001, Martin J. B. , Dean R. W. ,
Flow through carbonate aquifers may be dominated by conduits where they are present, by intergranular or fracture porosity where conduits are missing, or may occur in conduits and matrix porosity where both are well developed. In the latter case, the exchange of water between conduits and matrix could have important implications for water management and hydrodynamic modeling. An extensive conduit system has been mapped by dye trace studies and cave diving exploration at the Santa Fe Sink/Rise system located in largely unaltered rocks of the Floridan aquifer of north-central Florida. In this area, the Santa Fe River flows underground at the River Sink and returns to the surface similar to 5 km to the south at a first magnitude spring called the River Rise. Limited data show that discharge is greater by 27-96% at the River Rise than at the Sink and that the downstream increase in discharge is inversely related to discharge of the river. Natural SO42- concentrations indicate that similar to 25% of the water discharging from the Rise originates from the Sink during low flow. Conversely, SO42- and other solute concentrations indicate that most of the water discharging from the Rise originates from the Sink during floods. Ar similar to 40% decrease in Na () and Cl (-) concentrations over a 5 1/2-month period at a down-gradient water supply well may reflect flow of dilute flood water from the conduits into and through the matrix at rates estimated to be between 9 and 65 m/day, Calcium concentrations remain constant through time at the well, although flood waters have similar to 90% lower Ca (2) concentrations than ground water, perhaps reflecting dissolution of the matrix rocks. This apparent exchange of water between matrix and conduits is important for regional ground water quality and dissolution reactions, (C) 2001 Published by Elsevier Science B.V

Water budget and vertical conductance for Lowry (Sand Hill) Lake in north-central Florida, USA, 2001, Motz L. H. , Sousa G. D. , Annable M. D. ,
Water-budget components and the vertical conductance were determined for Lowry (Sand Hill) Lake in north-central Florida, USA. In this type of lake, which interacts with both the surface-water and groundwater systems, the inflow components are precipitation, surface-water inflow, groundwater inflow, and direct runoff (i.e. overland flow), and the outflow components are evaporation, groundwater outflow, and surface-water outflow. In a lake and groundwater system that is typical of many karst lakes in Florida, a large part of the groundwater outflow occurs by means of vertical leakage through an underlying confining unit to a deeper, highly transmissive aquifer called the upper Floridan aquifer. The water-budget component that represents vertical leakage to the upper Floridan aquifer was calculated as a residual using the water-budget equation. For the 13 month period from August 1994 to August 1995, relative to the surface area of the lake, rainfall at Lowry Lake was 1.55 m yr(-1), surficial aquifer inflow was 0.79 m yr(-1), surface-water inflow was 1.92 m yr(-1), and direct runoff was 0.01 m yr(-1). Lake evaporation was 1.11 m yr(-1), and surface-water outflow was 1.61 m yr(-1). The lake stage increased 0.07 m yr(-1), and the vertical leakage to the upper Floridan aquifer was 1.48 m yr(-1). Surficial aquifer outflow from the lake was negligible. At Lowry Lake, vertical leakage is a major component of the water budget, comprising about 35% of the outflow during the study period. The vertical conductance (K-V/b), a coefficient that represents the average of the vertical conductances of the hydrogeologic units between the bottom of a lake and the top of he upper Floridan aquifer, was determined to be 2.51 x 10(-4) day(-1) for Lowry Lake. (C) 2001 Elsevier Science B.V. All rights. reserved

Comparisons Among Ground-Water Flow Models and Analysis of Discrepancies in Simulated Transmissivities of the Upper Floridan Aquifer in Ground-Water Flow Model Overlap Areas, 2001, Sepulveda N.

Discrepancies in simulated transmissivities of the Upper Floridan aquifer were identified in the overlap areas of seven ground-water flow models in southwest and west-central Florida. Discrepancies in transmissivity are generally the result of uncertainty and spatial variability in other aquifer properties. All ground-water flow models were used to simulate the potentiometric surface of the Upper Floridan aquifer for approximated steady-state conditions from August 1993 through July 1994 using the time-independent hydraulic properties assigned to the models. Specifiedhead and general-head boundary data used to generate boundary conditions appropriate to these models were obtained from the estimated annual average heads for the steady-state period. Water-use data and the approximated surficial aquifer system water table were updated to reflect conditions during the approximated steady-state period. Simulated heads at control points, vertical leakage rates to the Upper Floridan aquifer, and spring flows were used to analyze the discrepancies in transmissivities in model overlap areas. Factors causing transmissivity discrepancies in model overlap areas include differences among directly applied recharge rates, differences among model simulated vertical leakance values assigned to the overlaying confining unit resulting in varying leakage rates to the Upper Floridan aquifer, differences in heads and conductances used in general-head boundary cells, and differences in transmissivities assigned in the vicinity of springs. Additional factors include the grid resolution and algorithm used to approximate the heads of the surficial aquifer system when these are used as a source/sink layer. 


Exchange of Matrix and Conduit Water with Examples from the Floridan Aquifer, 2001, Martin J. D. , Screaton E. J.

Rapid infiltration of surface water and contaminants occurs in karst aquifers because of extensive conduit development, but contamination of ground water supplies requires loss of conduit water to the matrix. This process is also important for ground water management and for dissolution and diagenetic reactions. Many factors control exchange between conduits and matrix including the head gradient between matrix and conduits, the permeability of the matrix, the gradients of the regional water table and the conduits, and the relative elevation of the conduits and regional water table. The Floridan Aquifer, which is characterized by high matrix porosity and permeability, provides several examples. 


The Relation Between Structure and Saltwater Intrusion in the Floridan Aquifer System, Northeastern Florida, 2001, Spechler, R. M.

Saltwater intrusion is a potential threat to the quality of ground water in northeastern Florida. Elevated chloride concentrations have been observed in more than 70 wells tapping the Upper Floridan and the upper zone of the Lower Floridan aquifers. In Duval and northern St. Johns County, increased chloride concentrations in water from some wells along the coast and up to 14 miles inland indicate that saline water is gradually intruding into the freshwater zones of the Floridan aquifer system. Several mechanisms may explain this intrusion of saline water and the consequent increase in concentrations of chloride in northeastern Florida. The most plausible explanation is the upward movement of saline water along joints, fractures, collapse features, faults, or other structural anomalies. Land-based seismic reflection and marine seismic reflection profiles along the St. Johns River and off the coast of northeastern Florida show the presence of widely scattered solution collapse features in the Floridan aquifer system and overlying sediments. These features can create conduits of relatively high vertical conductivity, providing a hydraulic connection between freshwater zones and deeper, more saline zones. Lower heads caused by pumping from the shallower freshwater zones of the aquifer can result in an increased potential for upward movement of saline water through nearly vertical zones of preferential permeability. Saline water then can move laterally through the porous aquifer matrix or along horizontal fractures or solution zones within the aquifer toward well fields or other areas of lower hydraulic head


Sources of nitrate contamination and age of water in large karstic springs of Florida, 2004, Katz B. G. ,
In response to concerns about the steady increase in nitrate concentrations over the past several decades in many of Florida's first magnitude spring waters (discharge greater than or equal to2.8 m(3)/s), multiple isotopic and other chemical tracers were analyzed in water samples from 12 large springs to assess sources and timescales of nitrate contamination. Nitrate-N concentrations in spring waters ranged from 0.50 to 4.2 mg/L, and delta(15)N values of nitrate in spring waters ranged from 2.6 to 7.9 per mil. Most delta(15)N values were below 6 per mil indicating that inorganic fertilizers were the dominant source of nitrogen in these waters. Apparent ages of groundwater discharging from springs ranged from 5 to about 35-years, based on multi-tracer analyses (CFC-12, CFC-113, SF6, H-3/He-3) and a piston flow assumption; however, apparent tracer ages generally were not concordant. The most reliable spring-water ages appear to be based on tritium and He-3 data, because concentrations of CFCs and SF6 in several spring waters were much higher than would be expected from equilibration with modern atmospheric concentrations. Data for all tracers were most consistent with output curves for exponential and binary mixing models that represent mixtures of water in the Upper Floridan aquifer recharged since the early 1960s. Given that groundwater transit times are on the order of decades and are related to the prolonged input of nitrogen from multiple sources to the aquifer, nitrate could persist in groundwater that flows toward springs for several decades due to slow transport of solutes through the aquifer matrix

Conduit properties and karstification in the unconfined Floridan Aquifer, 2004, Screaton E. , Martin J. B. , Ginn B. , Smith L. ,
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 m(2), 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) m(3) 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

Matrix permeability of the confined Floridan Aquifer, Florida, USA, 2004, Budd Da, Vacher Hl,
The Upper Floridan Aquifer of peninsular Florida retains most of its depositional porosity and, as a result, is a multi-porosity aquifer: double porosity (fractured porous aquifer) downdip where the aquifer is confined, and triple porosity (karstic, fractured porous aquifer) in the updip, unconfined region. Matrix permeability in the confined region varies in the range <10(-14.41)-10(-11.1) m(2), as determined by 12,000 minipermeameter measurements on 1,210 m of slabbed core. Limestones divide into 13 textural classes and dolomites into two. Depositional facies (textural class) strongly correlates with matrix permeability. As a result, the facies architecture of the Eocene and Oligocene carbonates that compose the confined portion of the aquifer controls the lateral and vertical distribution of its matrix transmissivity. The most-permeable facies are grainstones (median k, 10(-12.4) m(2)) and sucrosic dolomites (median k, 10(-12.0) m(2)). Together, they are responsible for &SIM;73% of the matrix transmissivity of the logged cores, although they constitute only &SIM;24% of the thickness. Examination of the flow equations of fractured porous aquifers suggests that the permeability of these two facies is large enough that matrix permeability cannot be discounted in modeling the hydraulics of the double-porosity system. This conclusion likely applies to most, if not all, Cenozoic double-porosity carbonate aquifers, as average matrix and fracture permeabilities in the Floridan Aquifer are similar to other Cenozoic carbonates from around the world

Using Multiple Chemical Indicators to Assess Sources of Nitrate and Age of Groundwater in a Karstic Spring Basin, 2005, Katz Brian, Copeland Rick, Greenhalgh Tom, Ceryak Ron, Zwanka Warren,
Human health and ecological concerns have arisen due to a steady increase in nitrate-N concentrations during the past 40 years in Fannin Springs (0.3-4.7 mg/L), a regional discharge point with an average flow of >2.8 m3/second (>100 ft3/second) for water from the karstic Upper Floridan aquifer (UFA). Multiple chemical indicators (major dissolved species, 15N and 18O of nitrate, dissolved gases, 78 pesticides and degradates, and 67 organic compounds typically found in domestic and industrial wastewater) and transient tracers (3H/3He, chlorofluorocarbons [CFCs], sulfur hexafluoride [SF6]) were analyzed in water samples from nine wells along three transects and in spring water to assess groundwater age and potential contaminant sources. Land use is predominantly agricultural (52 percent) and forest (31 percent) in the 320 km2 (124 mi2) spring basin, which was delineated from a potentiometric-surface map of the UFA using high-resolution water-level data. Nitrate-N concentrations were highly variable in the oxic UFA and ranged from <0.02 to 4.7 mg/L. {delta}15N-NO3 values (3.4-9.9 per mil) indicated that nitrate contamination originated from inorganic sources (synthetic fertilizer) and organic sources (manure spreading or waste disposal). Higher nitrate concentrations and the younger age of spring water relative to water from upgradient wells indicate better communication with N sources at the surface. Apparent ages of groundwater correlated positively with well depth (P < 0.05) and were younger in water from wells nearer to the spring (<8 years) compared with other wells (10-50 years). Most transient tracer concentrations were consistent with binary mixing curves representing mixtures of water recharged during the past 10 years and older water (recharged before 1940). Young water mixing fractions ranged from 0.07 to 0.90. Trace levels of herbicides found in groundwater and spring water were indicative of applications for vegetative control in agricultural and other land-use types

Architecture of air-filled caves within the karst of the Brooksville Ridge, west-central Florida., 2006, Florea, L. J.
Air-filled caves surveyed in the Brooksville Ridge of west-central Florida provide insight into the organization of karstic permeability within the unconfined portions of the Upper Floridan Aquifer. The morphology of the passages that compose these caves in geologically young, high-permeability limestones is strikingly different from caves found in ancient carbonates far from the influence of the coast. Cave passages in west-central Florida are laterally extensive and tiered. Principal horizons of cave development occur between +3 m and +5 m, +12 m and +15 m, and +20 m and +22 m above modern sea level. The primary guide of cave passage orientations within these cave levels is widespread fractures oriented approximately NE-SW and NW-SE. Cave passages of human dimensions form at the intersection of the laterally extensive cavities and fractures and often acquire a characteristic plus-sign shape. The walls of cave passages in west-central Florida are porous and complex, with small-scale solution features such as pockets and tafoni structures extending into the host bedrock. Additionally, these cave passages often end in blind pockets, ever-narrowing fissures, sediment fills, and collapses. The passages do not appear to represent an integrated system of conduits between aquifer inputs and outputs.

Textural and stratigraphic controls on fractured dolomite in a carbonate aquifer system, Ocala limestone, west-central Florida, 2006, Gaswirth Sb, Budd Da, Crawford Br,
The Late Eocene Ocala Limestone is part of the Upper Floridan Aquifer, and in west-central Florida the Ocala forms a subregional semi-confining unit that separates underlying and overlying highly transmissive zones. In portions of the same area, the lower half of the Ocala is dolomitized and fractures are observed in cores. Where present, the fractures should locally enhance the hydraulic conductivity of the dolomite and could enhance vertical leakage through the semi-confining Ocala interval.Triaxial strength tests and Brazilian Disc tensile tests were conducted on a suite of 2.5-cm diameter dolomite core plugs from five boreholes. Samples were texturally subdivided on the basis of degree of induration into three general categories: friable sucrosic dolomite with high porosity, moderately indurated dolomite with intermediate porosity, and tightly indurated dolomite with low porosity. Results indicate elevated cohesion magnitude and tensile strength as the degree of induration increases and secondarily as abundance of moldic porosity decreases. Sucrosic and moderately indurated dolomites are most likely to fracture due to their low cohesion strength, followed by tightly indurated dolomites with high moldic porosity. Tightly indurated dolomite with little or no moldic porosity is the least likely to fracture.Degree of dolomite induration is a function of the lime precursor's depositional fabric. Thus, combining strength data with known stratigraphic patterns in depositional textures allows for prediction of mechanical units and fractured horizons in the Ocala dolomites, and provides insight into regions of potentially increased hydraulic conductivity

Mixing of shallow and deep groundwater as indicated by the chemistry and age of karstic springs, 2006, Toth D. J. , Katz B. G.

Large karstic springs in east-central Florida, USA were studied using multi-tracer and geochemical modeling techniques to better understand groundwater flow paths and mixing of shallow and deep groundwater. Spring water types included Ca–HCO3 (six), Na–Cl (four), and mixed (one). The evolution of water chemistry for Ca– HCO3 spring waters was modeled by reactions of rainwater with soil organic matter, calcite, and dolomite under oxic conditions. The Na–Cl and mixed-type springs were modeled by reactions of either rainwater or Upper Floridan aquiferwater with soil organic matter, calcite, and dolomite under oxic conditions and mixed with varying proportions of saline Lower Floridan aquifer water, which represented 4–53% of the total spring discharge. Multiple-tracer data—chlorofluorocarbon CFC-113, tritium (3H), helium- 3 (3Hetrit), sulfur hexafluoride (SF6)—for four Ca–HCO3 spring waters were consistent with binary mixing curves representing water recharged during 1980 or 1990 mixing with an older (recharged before 1940) tracer-free component. Young-water mixing fractions ranged from 0.3 to 0.7. Tracer concentration data for two Na–Cl spring waters appear to be consistent with binary mixtures of 1990 water with older water recharged in 1965 or 1975. Nitrate-N concentrations are inversely related to apparent ages of spring waters, which indicated that elevated nitrate-N concentrations were likely contributed from recent recharge.


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