Pollen census data from southern Florida: Sites along a nutrient gradient in Water Conservation Area 2A
No abstract available.
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Geology topics
Research about Florida
Source-linked reports with geographic coverage including Florida.
Water resources data, Florida, water year 1996; Volume 2A. South Florida surface water
The Water Resources Division of the U.S. Geological Survey, in cooperation with State, County, and other Federal agencies, obtains a large amount of data pertaining to the water resources of Florida each water year. These data, accumulated during many water years, constitute a valuable data base for developing an improved understanding of the water resources of the State. To make these data readily available to interested parties outside the Geological Survey, the data are published annually in this report series entitled "Water Resources Data - Florida, Volume 2A: South Florida Surface Water and Volume 2B: South Florida Ground Water."
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Water resources data, Florida, water year 1996. Volume 2B: South Florida - ground water
Water resources data for 1996 water year in Florida consists of continuous or daily discharge for 319 streams, periodic discharge for 41 streams, continuous or daily stage for 97 streams, periodic stage for 8 streams, peak discharge for 35 streams, and peak stage for 12 streams; continuous or daily elevations for 30 lakes, periodic elevations for 56 lakes; continuous ground-water levels for 417 wells, periodic groundwater levels for 1,370 wells; quality of water data for 113 surface-water sites and 279 wells. The data for South Florida included continuous or daily discharge for 73 streams, continuous or daily stage for 76 streams, peak stage discharge for no streams, continuous elevation for 1 lake; continuous groundwater levels for 222 wells, periodic ground-water levels for 772 wells and no miscellaneous water-level measurements; quality-of-water for 29 surface-water sites and 207 wells. The data represent the National Water Data System records collected by the U.S. Geological Survey and cooperation with local, state, and federal agencies in Florida.
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Water resources data, Florida, water year 1997; Volume 3A. Southwest Florida surface water
The Water Resources Division of the U.S. Geological Survey, in cooperation with State agencies, obtains a large amount of data pertaining to the water resources of Florida each water year. These data, accumulated during many water years, constitute a valuable data base for developing an improved understanding of the water resources of the State. To make these data readily available to interested parties outside the Geological Survey, the data are published annually in this report series entitled "Water Resources Data - Florida."
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The relation between hydrogeology and water quality of the Lower Floridan Aquifer in Duval County, Florida, and implications for monitoring movement of saline water
The hydrogeology of the Upper zone of the Lower Floridan aquifer and its relation to water quality were evaluated during a 3-year (1993-96) study. The Floridan aquifer system, a carbonate aquifer system composed of the Upper Floridan aquifer, a middle semi-confining unit, and the Lower Floridan aquifer, is the major source of water supply in northeastern Florida. The Lower Floridan aquifer is further subdivided into the Upper zone, a semi-confining unit, and the Fernandina permeable zone. As a result of increased withdrawals, heads in the aquifer system have declined and at the same time chloride concentrations have increased in the water from many wells in Duval County. A better understanding of the sources of and pathways for movement of brackish water is needed so that water managers can monitor the movement of brackish water and plan future water development. Most of the wells in Duval County deeper than 900 feet penetrate the Upper Floridan aquifer and the Upper zone of the Lower Floridan aquifer. Transmissivity estimates for these zones range from 2,000 to 194,000 feet squared per day. Permeability in the Upper zone of the Lower Floridan aquifer is primarily related to secondary porosity developed along bedding planes, joints, and fractures as a result of paleokarst processes. The Upper zone is about 300 to 500 feet thick in Duval County, based on the geophysical logs of about 40 wells ranging in depth from about 1,000 to 2,200 feet. In some areas the Upper zone has a single flow zone, but in other areas, two distinct flow zones are apparent. Water samples collected during this study confirm the continued increase in chloride concentrations in both the Upper Floridan aquifer and the Upper zone of the Lower Floridan aquifer. Most of the observed increases are in the eastern part of the county, but a pattern in the locations of wells yielding water with chloride increases is not discernible. In some areas, zones bearing brackish water are underlain by zones of fresher water, but in other areas, fresher water was not found beneath the brackish water. A single fracture or solution feature was the source of brackish water in several wells. The most likely source of brackish water to the Upper zone of the Lower Floridan aquifer is the underlying Fernandina permeable zone, which contains freshwater in the western part of the county but saline water in the eastern part. The pathways for movement of saline water are interconnecting vertical and horizontal fracture or solution zones probably developed along paleokarst features that are not mappable from the land surface; therefore, a conventional monitor-well network probably would not provide early warning of saline-water intrusion. Continued monitoring of water-quality trends in water-supply wells, combined with collection of additional surface and borehole geophysical data, can provide an increased understanding of the movement of brackish water in the Floridan aquifer system.
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Delineation and extent of saltwater intrusion in the Biscayne aquifer, eastern Dade County, Florida, 1995
No abstract available.
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An optimized network for phosphorus load monitoring for Lake Okeechobee, Florida
Phosphorus load data were evaluated for Lake Okeechobee, Florida, for water years 1982 through 1991. Standard errors for load estimates were computed from available phosphorus concentration and daily discharge data. Components of error were associated with uncertainty in concentration and discharge data and were calculated for existing conditions and for 6 alternative load-monitoring scenarios for each of 48 distinct inflows. Benefit-cost ratios were computed for each alternative monitoring scenario at each site by dividing estimated reductions in load uncertainty by the 5-year average costs of each scenario in 1992 dollars. Absolute and marginal benefit-cost ratios were compared in an iterative optimization scheme to determine the most cost-effective combination of discharge and concentration monitoring scenarios for the lake. If the current (1992) discharge-monitoring network around the lake is maintained, the water-quality sampling at each inflow site twice each year is continued, and the nature of loading remains the same, the standard error of computed mean-annual load is estimated at about 98 metric tons per year compared to an absolute loading rate (inflows and outflows) of 530 metric tons per year. This produces a relative uncertainty of nearly 20 percent. The standard error in load can be reduced to about 20 metric tons per year (4 percent) by adopting an optimized set of monitoring alternatives at a cost of an additional $200,000 per year. The final optimized network prescribes changes to improve both concentration and discharge monitoring. These changes include the addition of intensive sampling with automatic samplers at 11 sites, the initiation of event-based sampling by observers at another 5 sites, the continuation of periodic sampling 12 times per year at 1 site, the installation of acoustic velocity meters to improve discharge gaging at 9 sites, and the improvement of a discharge rating at 1 site.
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Simulation of subsurface storage and recovery of effluent using multiple wells, St Petersburg, Florida
The potential for subsurface storage and recovery, otherwise called aquifer storage and recovery, of effluent in the uppermost producing zone of the Upper Floridan aquifer in St. Petersburg, Florida, was studied by the U.S. Geological Survey, in cooperation with the city of St. Petersburg and the Southwest Florida Water Management District. The success of subsurface storage and recovery depends on the recovery efficiency, or the quantity of water, relative to the quantity injected, that can be recovered before the water that is withdrawn fails to meet salinity limits. The viability of this practice will depend upon the ability of the injected zone to receive, store, and discharge the injected fluid. A three-dimensional numerical model of ground-water flow and solute transport, incorporating available data on aquifer properties and water quality, was developed to evaluate the effects of changing various operational factors on recovery efficiency. The reference case for testing was a base model considered representative of the aquifer system underlying the Southwest St. Petersburg Water Treatment Facility. The base simulation used as a standard for comparison consisted of a single cycle of 90 days of simultaneous injection of effluent in three wells at a rate of 4.0 million gallons per day and then equal rate withdrawal of 4.0 million gallons per day until the pumped water in each well reached a dissolvedsolids concentration of 1,500 milligrams per liter. A recovery efficiency of 14.8 percent was estimated for the base simulation. Ten successive injection and recovery cycles increased recovery efficiency to about 56 percent. Based on model simulations for hypothetical conditions, recovery efficiency (1) increased with successive injection and recovery cycles; (2) increased when the volume of injectant increased; (3) decreased when storage time increased; (4) did not change significantly when the injection rate or recovery rate increased, or when the ratio of recovery rate to injection rate increased, and (5) was not significantly affected by any particular geometric arrangement of wells or by the number of wells when the volume of water injected remained constant. Recovery efficiency from multiple wells was nearly the same as from a single well. Recovery efficiency ranged from about 7 to 56 percent, in several tests. Sensitivity of recovery efficiency to variations in selected parameters such as dissolved-solids concentration of the injection zone, permeability, vertical anisotropy, longitudinal and transverse dispersivities, and effective porosity was tested. Changes in the dissolved-solids concentration of the injection zone produced the greatest change in recovery efficiency. Uniform changes in dispersivity values produced the second greatest change in recovery efficiency. Generally, recovery efficiency increased when the above parameter values were decreased and recovery efficiency decreased when these parameter values were increased. Density difference between native and injected waters was the most important factor affecting recovery efficiency in this study. For the base simulation, sensitivity tests indicated that recovery efficiency increased from about 15 to 78 percent when the dissolved-solids concentration of the native water decreased from about 7,800 to 500 milligrams per liter. Dispersivity is another important factor affecting recovery efficiency. For the base simulation, sensitivity tests indicated that recovery efficiencies from about 9 to 24 percent can be obtained for different dispersivity values. A field determination of dispersivity was not made as part of this study, and values used may not be representative of the actual dispersive characteristics of the aquifer system at the study site. However, dispersivity values tested are within the range of values used in previous studies.
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Review of selected features of the natural system model, and suggestions for applications in south Florida
A study was conducted to review selected features of the Natural System Model, version 4.3. The Natural System Model is a regional-scale model that uses recent climatic data and estimates of historic vegetation and topography to simulate pre-canal-drainage hydrologic response in south Florida. Equations used to represent the hydrologic system and the numerical solution of these equations in the model were documented and reviewed. Convergence testing was performed using 1965 input data, and selected other aspects of the model were evaluated. Some conclusions from the evaluation of the Natural System Model include the following observations. Simulations were generally insensitive to the temporal resolution used in the model. However, reduction of the computational cell size from 2-mile by 2-mile to 2/3-mile by 2/3-mile resulted in a decrease in spatial mean ponding depths for October of 0.35 foot for a 3-hour time step. Review of the computer code indicated that there is no limit on the amount of water that can be transferred from the river system to the overland flow system, on the amount of seepage from the river to the ground-water system, on evaporation from the river system, or on evapotranspiration from the overland-flow system. Oscillations of 0.2 foot or less in simulated river stage were identified and attributed to a volume limiting function which is applied in solution of the overland-flow equations. The computation of the resistance coefficient is not consistent with the computation of overland-flow velocity. Ground-water boundary conditions do not always ensure a no-flow condition at the boundary. These inconsistencies had varying degrees of effects on model simulations, and it is likely that simulations longer than 1 year are needed to fully identify effects. However, inconsistencies in model formulations should not be ignored, even if the effects of such errors on model results appear to be small or have not been clearly defined. The Natural System Model can be a very useful tool for estimating pre-drainage hydrologic response in south Florida. The model includes all of the important physical processes needed to simulate a water balance. With a few exceptions, these hydrologic processes are represented in a reasonable manner using empirical, semiempirical, and mechanistic relations. The data sets that have been assembled to represent physical features, and hydrologic and meteorological conditions are quite extensive in their scope. Some suggestions for model application were made. Simulation results from the Natural System Model need to be interpreted on a regional basis, rather than cell by cell. The available evidence suggests that simulated water levels should be interpreted with about a plus or minus 1 foot uncertainty. It is probably not appropriate to use the Natural System Model to estimate pre-drainage discharges (as opposed to hydroperiods and water levels) at a particular location or across a set of adjacent computational cells. All simulated results for computational cells within about 10 miles of the model boundaries have a higher degree of uncertainty than results for the interior of the model domain. It is most appropriate to interpret the Natural System Model simulation results in connection with other available information. Stronger linkages between hydrologic inputs to the Everglades and the ecological response of the system would enhance restoration efforts.
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Hydrologic and water-quality conditions in the Horse Creek basin, west-central Florida, October 1992-February 1995
A baseline study of the 241-square-mile Horse Creek basin was undertaken from October 1992 to February 1995 to assess the hydrologic and water-quality conditions of one of the last remaining undeveloped basins in west-central Florida. During the period of the study, much of the basin remained in a natural state, except for limited areas of cattle and citrus production and phosphate mining. Rainfall in 1993 and 1994 in the Horse Creek basin was 8 and 31 percent, respectively, above the 30-year long-term average. The lowest and highest maximum instantaneous peak discharge of the six daily discharge stations occurred at the Buzzard Roost Branch and the Horse Creek near Arcadia stations with 185 to 4,180 cubic feet per second, respectively. The Horse Creek near Arcadia station had the lowest number of no-flow days with zero days and the Brushy Creek station had the highest number with 113 days. During the study, the West Fork Horse Creek subbasin had the highest daily mean discharge per square mile with 30.6 cubic feet per second per square mile, and the largest runoff coefficient of 43.7 percent. The Buzzard Roost Branch subbasin had the lowest daily mean discharge per square mile with 5.05 cubic feet per second per square mile, and Brushy Creek and Brandy Branch shared the lowest runoff coefficient of 0.6 percent. Brandy Branch had the highest monthly mean runoff in both 1993 and 1994 with 11.48 and 19.28 inches, respectively. During the high-baseflow seepage run, seepage gains were 8.87 cubic feet per second along the 43-mile Horse Creek channel. However, during the low-baseflow seepage run, seepage losses were 0.88 cubic foot per second. Three methods were used to estimate average annual ground-water recharge in the Horse Creek basin: (1) well hydrograph, (2) chloride mass balance, and (3) streamflow hydrograph. Estimated average annual recharge using these three methods ranged from 3.6 to 8.7 inches. The high percentage of carbonate plus bicarbonate analyzed at the Carlton surficial aquifer well could indicate an upward ground-water flow from the underlying intermediate aquifer system. Based on constituent concentrations in water samples from the six daily discharge stations, concentrations generally are lower in the upper three subbasins, West Fork Horse Creek, Upper Horse Creek, and Brushy Creek than in the lower three subbasins. Typically, concentrations were highest for major ions at Buzzard Roost Branch and nutrients at Brushy Creek.
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Application of acoustical methods for estimating water flow and constituent loads in Perdido Bay, Florida
Water flow and quality data were collected from December 1994 to September 1995 to evaluate variations in discharge, water quality, and chemical fluxes (loads) through Perdido Bay, Florida. Data were collected at a cross section parallel to the U.S. Highway 98 bridge. Discharges measured with an acoustic Doppler current profiler (ADCP) and computed from stage-area and velocity ratings varied roughly between + or - 10,000 cubic feet per second during a typical tidal cycle. Large reversals in flow direction occurred rapidly (less than 1 hour), and complete reversals (resulting in near peak net-upstream or downstream discharges) occurred within a few hours of slack water. Observations of simultaneous upstream and downstream flow (bidirectional flow) were quite common in the ADCP measurements, with opposing directions of flow occurring predominantly in vertical layers. Continuous (every 15 minutes) discharge data were computed for the period from August 18, 1995, to September 28, 1995, and filtered daily mean discharge values were computed for the period from August 19 to September 26, 1995. Data were not computed prior to August 18, 1995, either because of missing data or because the velocity rating was poorly defined (because of insufficient data) for the period prior to landfall of hurricane Erin (August 3, 1995). The results of the study indicate that acoustical techniques can yield useful estimates of continuous (instantaneous) discharge in Perdido Bay. Useful estimates of average daily net flow rates can also be obtained, but the accuracy of these estimates will be limited by small rating shifts that introduce bias into the instantaneous values that are used to compute the net flows. Instantaneous loads of total nitrogen ranged from -180 to 220 grams per second for the samples collected during the study, and instantaneous loads of total phosphorous ranged from -10 to 11 grams per second (negative loads indicate net upstream transport). The chloride concentrations from the water samples collected from Perdido Bay indicated a significant amount of mixing of saltwater and freshwater. Mixing effects could greatly reduce the accuracy of estimates of net loads of nutrients or other substances. The study results indicate that acoustical techniques can yield acceptable estimates of instantaneous loads in Perdido Bay. However, estimates of net loads should be interpreted with great caution and may have unacceptably large errors, especially when saltwater and freshwater concentrations differ greatly.
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Spring contributions to water quantity and nitrate loads in the Suwannee River during base flow in July 1995
The Suwannee River flows through an area of north-central Florida where ground water has elevated nitrate concentrations. A study was conducted to determine how springs and other ground-water inflow affect the quantity and quality of water in the Suwannee River. The study was done on a 33-mile (mi) reach of the lower Suwannee River from just downstream of Dowling Park, Fla., to Branford, Fla. Water samples for nitrate concentrations (dissolved nitrite plus nitrate as nitrogen) and discharge data were collected at 11 springs and 3 river sites during the 3-day period in July 1995 during base flow in the river. In the study reach, all inflow to the river is derived from ground water. Measured springs and other ground-water inflow, such as unmeasured springs and upward diffuse leakage through the riverbed, increased the river discharge 47 percent over the 33-mi reach. The 11 measured springs contributed 41 percent of the increased discharge and other ground-water inflow contributed the remaining 59 percent. River nitrate loads increased downstream from 2,300 to 6,000 kilograms per day (kg/d), an increase of 160 percent in the 33-mi study reach. Measured springs contributed 46 percent of this increase and other ground-water inflow contributed the remaining 54 percent. The study reach was divided at Luraville, Fla., into an 11-mi upper segment and a 22-mi lower segment to determine whether the ground-water inflows and nitrate concentrations were uniform throughout the entire study reach (fig. 1). The two segments were dissimilar. The amount of water added to the river by measured springs more than tripled from the upper to the lower segment. Even though the median nitrate concentration for the three springs in the upper segment (1.7 milligrams per liter (mg/L)) was similar to the median for the eight springs in the lower segment (1.8 mg/L), nitrate concentrations in the river almost doubled from 0.46 to 0.83 mg/L in the lower segment. Only 11 percent of the increase in nitrate load for the study reach occurred in the upper segment; the remaining 89 percent occurred in the lower segment. Measured springs were the major source of nitrate load in the upper reach and other ground-water inflow was the major source in the lower segment. Differences in nitrate loads between the upper and lower river segments are probably controlled by such factors as differences in the magnitude of the spring discharges, the size and location of spring basins, and the hydrologic characteristics of ground water in the study area.
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Tests of subsurface storage of freshwater at Hialeah, Dade County, Florida, and numerical simulation of the salinity of recovered water
Injection and observation wells were drilled in late 1974 for the purpose of conducting tests of storage and recovery of potable water in the brackish Upper Floridan aquifer. Three tests, involving storage and recovery cycles of varying volumes and storage period lengths, were performed between July 1975 and January 1980. Recovery was by natural artesian flow, and recovery efficiencies were 32.9, 47.8, and 38.5 percent. Wellbore plugging occurred during the injection stages, but injectivity was restored by periodic 2- to 3-hour backflushes at the natural artesian flow rate. An interval of shelly limestone between 1,015 and 1,050 feet below land surface contained the flow zone. Data from an analysis of 18 spinner flowmeter logs indicated that the principal part of the flow zone extended from 1,024 to 1,036 feet below land surface and that minor amounts of flow occurred to a depth of about 1,047 feet. A neutron porosity log indicated the bulk porosity of both the flow zone and confining layers to be 35 percent. Chloride and dissolved-solids concentrations of water in the flow zone were 1,200 and 2,700 milligrams per liter, respectively. A three-dimensional, finite-difference flow and solute-transport code was used to simulate pressure data measured during an aquifer test and observed salinity increases in recovered water during storage and recovery cycles. The aquifer test conducted in February 1975 was simulated by using a hydraulic conductivity estimate of 800 feet per day and a rock compressibility estimate of 0.0000400 (pound per square inch)-1. The equivalent transmissivity and storage coefficients were 9,600 cubic feet per day per square foot times foot of aquifer thickness and 7.8×10-5, respectively. Simulation of observed salinity increases during the three recoveries required dispersivities of 65 feet, a molecular diffusivity of 0.0002 foot squared per day, and a regional pore velocity of 260 feet per year. Central differencing in space and time was used for the solute-transport computations as well as an experimental method of computing vertical dispersion that used a scaling factor of 0.013. Additional simulations of the aquifer-test data and recovery salinities were obtained based on assumptions that (1) the flow zone was 21 feet thick, (2) flow-zone effective porosity was 20 percent, and (3) flow-zone hydraulic conductivity was bipolar anisotropic by a ratio of 10:1. The four sets of simulation values were used in model runs in which 10 years of annual injection, storage, and recovery cycles were simulated. Computed recovery efficiencies increased from 40 percent in the first year to 68 percent in later cycles. The high regional pore velocity required for model calibration substantially limited the recovery efficiency achieved in later cycles.
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