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Research about Florida

Source-linked reports with geographic coverage including Florida.

At least 1,441 records · Page 80Linked to original sources
USGS1996

Effects of nutrients and hydroperiod on Typha, Cladium, and Eleocharis: Implications for everglades restoration

The recent expansion of Typha domingensis ( Typha ) into areas of the Everglades previously dominated by Cladium jamaicense ( Cladium ) communities has led to competing hypotheses about the importance of nutrient concentration vs. hydroperiod in controlling the distribution of these species. In this study, experimental mixtures of Typha domingensis , Cladium jamaicense , and Eleocharis interstincta ( Eleocharis ), a member of the Cladium community, were subjected to two levels of nutrient concentration and three contrasting hydroperiods to determine how these variables might affect Typha 's ability to displace the Cladium community. Mixtures of the three species were established in outdoor tanks containing soil from the northern Everglades region where the experiment was conducted. Nutrient treatments consisted of nutrient additions to adjust ambient water concentrations to either 50 μg/L phosphorus (P) or 100 μg/L P plus nitrogen (N). The three hydroperiods were achieved by maintaining water depths within ranges observed in the northern Everglades. Maximum water depths of 15, 30, and 60 cm were established throughout the wet season (May‐November) followed by lowering to 5 cm during the dry season. Over a 2‐yr period, biomass was monitored nondestructively and aboveground material was harvested at the end of the experiment. Analysis of the biomass changes over time showed that differences between the species developed by the end of the first growing season. Typha and Eleocharis had initial growth rates substantially higher than those observed for Cladium . Typha 's growth in mixtures responded positively to both elevated nutrients (by as much as 45%) as well as to increased water depth (by as much as 60%), while Cladium and Eleocharis did not increase in response to these variables. Tissue P concentrations were found to be higher for Typha and Eleocharis than for Cladium under nearly all conditions. Net accumulation of P in Typha shoots was 2‐3 times greater than in the other species. The enhancement of Typha by elevated nutrients and increased flooding is associated with a syndrome of life history characteristics that includes rapid growth rates, high tissue concentrations of P, tall leaves, and a greater response to contrasting environmental conditions. Cladium , in contrast, showed a slow growth rate, low tissue concentrations of P, a greater capacity to resist invasion by Typha in shallow waters, and less of a growth response to contrasting environmental conditions, traits that would seem to be well suited to the nutrient‐poor, hydrologically unstable conditions natural to the Everglades. Results from this study suggest that attempts to limit the spread of Typha should consider hydrologic restoration as well as reduction in surface water nutrients.

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USGS1996

The south Florida environment: A region under stress

This report provides an overview of the environmental setting in South Florida and serves as review and framework for developing U.S. Geological Survey programs in the region. The report describes the predevelopment and the current (present-day) environmental conditions in South Florida with emphasis on the quantity and quality of water. The geographical area covered is the southern one-half of the State and includes the South Florida National Water-Quality Assessment study area and adjacent coastal waters. This study area covers about 19,500 square miles and is the watershed of the larger regional ecosystem. The regional ecosystem includes the coastal waters between Charlotte Harbor on the Gulf of Mexico and the St. Lucie River on the Atlantic Ocean and the lands that drain into these waters.

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USGS1996

South Florida Ecosystem Program: Quantifying freshwater discharge for coastal hydraulic control structures in eastern Dade County, Florida

The South Florida Ecosystem Restoration Program is an intergovernmental effort, involving a number of agencies, to reestablish and maintain the ecosystem of south Florida. One element of the restoration effort is the development of a firm scientific basis for resource decision making. The U.S. Geological Survey (USGS), one of the agencies, provides scientific information as part of the South Florida Ecosystem Restoration Program. The USGS began their ow program, called the South Florida Ecosystem Program, in fiscal year 1995 for the purpose of gathering hydrologic, cartographic, and geologic data that relate to the mainland of south Florida, Florida Bay, and the Florida Keys and Reef ecosystems. As part of the South Florida Ecosystem Program, the USGS, in cooperation with the South Florida Water Management District (SFWMD), has conducted a study to determine discharge ratings for 16 coastal hydraulic control structures in eastern Dade County, Fla. Discharge data are needed to quantify water that can be made available for water supply and ecosystem restoration and to calibrate regional hydrologic models.

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USGS1996

South Florida Ecosystem Program; gaging flows in northeastern Florida Bay

Introduction The South Florida Ecosystem Restoration Program is an intergovernmental effort, involving a number of agencies, to reestablish and maintain the ecosystem of south Florida. One element of the restoration effort is the development of a firm scientific basis for resource decision making. The U.S. Geological Survey (USGS), one of the agencies, provides scientific information as part of the South Florida Ecosystem Restoration Program. The USGS began their own program, called the South Florida Ecosystem Program , in fiscal year 1995 for the purpose of gathering hydrologic, cartographic, and geologic data that relate to the mainland of south Florida, Florida Bay, and the Florida Keys and Reef ecosystems. Management of the south Florida ecosystem involves the use of hydrologic models that simulate the flow of water through the region. As sheetflow is reestablished by flow management in the wetlands of the Everglades, it is expected that changes will also be reflected in the amount of freshwater exiting the mainland through the principal streams or as sheetflow into Florida Bay. Several agencies, including the USGS and the U.S. Army Corps of Engineers (COE), are planning to use hydrologic models to simulate and predict the flows into Florida Bay and the circulation patterns within the bay itself. These models can then be used to determine the effects that management of the inland water system will have on the amount of freshwater the bay receives from the mainland. This project will provide modelers with essential flow and specific conductance data along the mangrove zone where data have not been previously available.

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USGS1996

Vegetation affects water movement in the Florida Everglades

Introduction The Florida Everglades is a vast, diverse wetland ecosystem characterized by small ground-surface slopes, slowly moving surface waters, and dense aquatic vegetation. Both submersed and emergent vegetation are found in sawgrass and cattail marshes, wet prairies, and sloughs. The south Florida ecosystem has been greatly altered during the last 100 years. A complex water-management system that includes levees, canals, pumps, and water-control structures now regulates flooding and provides a steady supply of fresh water to urban areas and agriculture. Drainage projects have diverted much of the water that originally flowed slowly southward from Lake Okeechobee through the Everglades. Restoration and management of the Everglades ecosystem requires understanding and manipulating the amount and timing of water flows throughout the ecosystem. The spatial and temporal distribution of water and water-borne contaminants in the Everglades must be understood if degradation of the ecosystem is to be halted and reversed. To understand how water moves through the Everglades, it is necessary to quantify the forces affecting the flow. The resistance exerted on the flow by the vegetation through which the water moves is one of the dominant but least understood forces affecting Everglades surface-water flows. The aquatic vegetation of the Everglades affects both the depth of water and the rate at which it moves. The presence of living and dead plant material in the water column creates drag forces on the moving water. Water flows most slowly and the water-surface slope is largest in areas where vegetation is most dense.

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USGS1996

Regional evaluation of evapotranspiration in the Everglades

Understanding the water budget of the Everglades system is crucial to the success of restoration and management strategies. Although the water budget is simple in concept, it is difficult to assess quantitatively. Models used to simulate changes in water levels and vegetation resulting from management strategies need to accurately simulate all components of the water budget. One of the most important components of the Everglades water budget is evapotranspiration (ET). ET is water removed from the surface and soils by direct evaporation and plant transpiration. In South Florida, ET rates may exceed 40 in/yr (inches per year) on the average; during dry years, the ET could exceed rainfall (about 50 in/yr). Thus, most of the water that falls on the land surface as rainfall is returned to the atmosphere by ET. Despite the importance of ET in the Everglades water budget, our knowledge of ET is, at present, only semi-quantitative. Recent advances in instrumentation and measurement techniques have made it possible to continuously measure ET, so that an accurate evaluation of ET in the Everglades can be made.

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USGS1996

Water flows and nutrient loads to the southwest coast of Florida—A study

Background The embayments and estuaries of Florida's southwest coast are an integral part of the south Florida ecosystem. Nutrients and other constituents are transported to these coastal waters by surface water and ground-water flow from the Everglades National Park (ENP) and the Big Cypress Preserve and by longshore and offshore tidal currents. The coastal area is an essential breeding ground for many estuarine and marine species and is a popular location for wilderness recreational pursuits as well as sport fishing. The volume of flow and the loads of nutrients being discharged from the streams draining the upland areas of ENP and Big Cypress Preserve currently are unknown. As part of Everglades restoration activities, the U.S. Army Corps of Engineers may change the volume or location of water deliveries to the ENP. Such changes could affect the volume or distribution of inflow and associated constituents that are transported into the coastal waters of southwest Florida. Proposals to change water deliveries to the Everglades National Park and efforts to improve the environmental health of Florida Bay cannot be evaluated without some understanding of the hydrologic and water-quality characteristics of tidal rivers and coastal embayments in the region. The southwest coast of Florida is part of a wilderness area with unique hydraulic characteristics that has historically been described as the "River of Grass." Flat terrain and lack of controlled topographic information has made it difficult to define drainage divides. Low gradients, coupled with tidal effects, create complex conditions under which to measure riverine flow. It has been almost thirty years since any effort has been made to monitor flow characteristics continuously in the area. Significant technological advancements have occurred during this time and this new technology can be applied to help obtain the information needed to make informed decisions about the future of this unique coastal area.

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USGS1996

Review and evaluation of a model for simulating the natural hydrology of South Florida

The South Florida Ecosystem Program is an intergovernmental effort to re-establish and maintain the ecosystem of South Florida. One element of the restoration effort is the development of a firm scientific basis for making management decisions. The U.S. Geologcal Survey (USGS) is one of the agencies that provides this needed scientific information through the USGS South Florida Ecosystem Program.

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USGS1996

Mercury and periphyton in the south Florida ecosystem

Background Advisories warning against the eating of game fish due to high concentrations (0.5 to 1.5 parts per million) of mercury are common in areas of Florida. When concentrations of mercury in fish are reported, it is primarily the compound methylmercury (MeHg), a neurotoxin, that is assumed present. MeHg has caused neurological damage in people in Japan and Iraq who ate food tainted with mercury. The goal of this project is to answer the question, "How does mercury produced in the aquatic environment of south Florida enter the food chain and become part of the body burden of animals such as game fish"? This project is part of the South Florida Ecosystems Program. As part of the mercury studies in the Florida Everglades element, the findings of this project will contribute to an understanding of the processes that cause mercury bioaccumulation.

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USGS1996

Interactions of mercury with dissolved organic carbon in the Florida Everglades

There has been increased awareness by both public and scientific communities over mercury contamination of game fish in South Florida. Effective management strategies for dealing with this problem will require a more thorough understanding of the factors and processes that result in the generation and transport of mercury, and control its reactivity in the Everglades. The role of mercury complexation by dissolved organic carbon (DOC) has been proposed by several investigators as a primary mechanism for the transport of mercury in aquatic systems. However, this relationship has been simply proposed based on a strong correlation between dissolved mercury and DOC concentrations in ground, lake and stream waters. Interactions with DOC may be an important process for controlling the transport and bioavailability of mercury. The issue of carbon reactivity in South Florida is especially relevant due to the high natural production of organic carbon in the peat soils and wetlands, the relatively high carbon content of shallow ground water systems in the region, the interactions of organic matter with mercury, other trace metals, and anthropogenic compounds, accumulation of organic carbon in corals and carbonate precipitates, and the potential changes in the quality and reactivity of dissolved organic carbon (DOC) resulting from land use practices. This study will attempt to meet the need to more clearly understand the dynamics of organic matter mercury interactions in the Florida Everglades by focusing research on the effect of dissolved organic carbon (DOC) on the transport and reactivity of Hg in the Everglades.

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USGS1996

Comparison of the South Florida natural system model with pre-canal Everglades hydrology estimated from historical sources

Preservation and restoration of the remaining Everglades ecosystem is focussed on two aspects: improving upstream water quality and improving 'hydropatterns' - the timing, depth and flow of surface water. Restoration of hydropatterns requires knowledge of the original pre-canal drainage conditions as well as an understanding of the soil, topo-graphic, and vegetation changes that have taken place since canal drainage began in the 1880's. The Natural System Model (NSM), developed by the South Florida Water Management District (SFWMD) and Everglades National Park, uses estimates of pre-drainage vegetation and topography to estimate the pre-drainage hydrologic response of the Everglades. Sources of model uncertainty include: (1) the algorithms, (2) the parameters (particularly those relating to vegetation roughness and evapotranspiration), and (3) errors in the assumed pre-drainage vegetation distribution and pre-drainage topography. Other studies are concentrating on algorithmic and parameter sources of uncertainty. In this study we focus on the NSM output -- predicted hydropattern -- and evaluate this by comparison with all available direct and indirect information on pre-drainage hydropatterns. The unpublished and published literature is being searched exhaustively for observations of water depth, flow direction, flow velocity and hydroperiod, during the period prior and just after drainage (1840-1920). Additionally, a comprehensive map of soils in the Everglades region, prepared in the 1940's by personnel from the University of Florida Agricultural Experiment Station, the U.S. Soil Conservation Service, the U.S. Geological Survey, and the Everglades Drainage District, is being used to identify wetland soils and to infer the spatial distribution of pre-drainage hydrologic conditions. Detailed study of this map and other early soil and vegetation maps in light of the history of drainage activities will reveal patterns of change and possible errors in the input to the NSM. Changes in the wetland soils are important because of their effects on topography (soil subsidence) and in their role as indicators of hydropattern.

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USGS1996

Geohydrology and potential for upward movement of saline water in the Cocoa well field, East Orange County, Florida

The Floridan aquifer system, an approximately 2,000-foot thick sequence of Eocene-age limestone and dolomite, is the main source of water supply in central Florida. Hydraulic conductivity is different in strata of different lithology and is the basis for separating the aquifer system into the Upper Floridan aquifer, a middle semi-confining unit, and the Lower Floridan aquifer. The coastal city of Cocoa withdraws about 26 million gallons of water per day from the Upper Floridan aquifer from a well field in east Orange County, about 25 miles inland. About 60 million gallons per day are withdrawn from the Upper Floridan aquifer and 56 million gallons per day from the Lower Floridan aquifer in the Orlando area, about 15 miles west of the Cocoa well field. Wells drilled in the Cocoa well field from 1955-61 yielded water with chloride concentrations ranging from 25-55 milligrams per liter. Soon after the wells were put in service, chloride concentrations increased; therefore, new wells were drilled further inland. Chloride concentrations in water from many of the new wells also have increased. Possible sources of saline water are lateral movement of relict seawater in the Upper Floridan aquifer from the east, regional upconing of saline water from the Lower Floridan aquifer or underlying older rocks, or localized upward movement of saline water through fractures. Several test wells were drilled to provide information about chloride concentration changes with depth and to monitor changes with time, including a multi-zone well drilled in 1965 (well C) and two wells drilled in the 1990's (wells R and S). Chloride concentrations have increased in the zone pumped by the supply wells (the upper 500 feet of the aquifer) and in the 1,351 to 1,357-foot deep zone of well C, but not in the two intervening zones. This indicates that the source of saline water is located laterally, rather than vertically, from the pumped zone in the area of well C. The potential for upward movement of saline water depends on the direction of the vertical hydraulic gradient and on the vertical hydraulic conductivity of the aquifer. A series of aquifer tests was run in 1993-94 and existing water-level and water-quality data were analyzed to evaluate the potential for upward movement of saline water in the well field. The transmissivity of the upper 500 feet of the aquifer is about 100,000 feet squared per day (the horizontal hydraulic conductivity is about 200 feet per day) and the storage coefficient is about 2x10-4. Horizontal hydraulic conductivities determined from slug tests of the three deepest zones of well C ranged from 20-50 feet per day. Vertical hydraulic conductivities probably do not exceed 0.05 feet per day. The vertical hydraulic gradient is determined by comparing water levels in the various zones, but because of density differences, unadjusted water levels in the deepest zone investigated cannot be directly compared to water levels in the overlying freshwater zones. The difference between environmental-water heads (adjusted for density differences) in the saline-water zone of well C and the overlying freshwater zone were calculated from measured water levels for the period 1966 to 1994. During most of this time period, the gradient was downward, indicating that saline water did not move upward. Upconing of saline water probably is not taking place in the center and western part of the well field, based on the low vertical hydraulic conductivity values estimated for the middle semi-confining unit, the generally downward vertical hydraulic gradient, and the constant chloride concentrations in the intermediate zones of well C. However, there is no information about the extent of the zone of low vertical hydraulic conductivity or about the direction of the vertical hydraulic gradient in the eastern part of the well field. Thus, increased chloride concentrations in supply wells in the eastern part of the well field could be caused either by lateral movement of saline water from the east, or by upward movement from the Lower Floridan aquifer if the low conductivity zone is thin or breached by fractures, or by a combination of both lateral and vertical movement.

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USGS1996

Analysis of tests of subsurface injection, storage, and recovery of freshwater in the lower Floridan aquifer, Okeechobee County, Florida

A series of freshwater subsurface injection, storage, and recovery tests were conducted at an injection-well site near Lake Okeechobee in Okeechobee County, Florida, to assess the recoverability of injected canal water from the Lower Floridan aquifer. At the study site, the Lower Floridan aquifer is characterized as having four local, relatively independent, high-permeability flow zones (389 to 398 meters, 419 to 424 meters, 456 to 462 meters, and 472 to 476 meters below sea level). Four subsurface injection, storage, and recovery cycles were performed at the Lake Okeechobee injection-well site in which volumes of water injected ranged from about 387,275 to 1,343,675 cubic meters for all the cycles, and volumes of water recovered ranged from about 106,200 to 484,400 cubic meters for cycles 1, 2, and 3. The recovery efficiency for successive cycles 2 and 3 increased from 22 to 36 percent and is expected to continue increasing with additional cycles. A comparison of chloride concentration breakthrough curves at the deep monitor well (located about 171 meters from the injection well) for cycles 1, 4, and test no. 4 (from a previous study) revealed unexpected finings. One significant result was that the concentration asymptote, expected to be reached at concentration levels equivalent or close to the injected water concentration, was instead reached at higher concentration levels. The injection to recovery rate ratio might affect the chloride concentration breakthrough curve at the deep monitor well, which could explain this unexpected behavior. Because there are four high-permeability zones, if the rate of injection is smaller than the rate of recovery (natural artesian flow), the head differential might not be transmitted through the entire open wellbore, and injected water would probably flow only through the upper high- permeability zones. Therefore, observed chloride concentration values at the deep monitor well would be higher than the concentration of the injected water and would represent a mix of water from the different high-permeability zones. A generalized digital model was constructed to simulate the subsurface injection, storage, and recovery of freshwater in the Lower Floridan aquifer at the Lake Okeechobee injection-well site. The model was constructed using a modified version of the Saturated-Unsaturated TRAnsport code (SUTRA), which simulates variable-density advective-dispersive solute transport and variable-density ground-water flow. Satisfactory comparisons of simulated to observed dimensionless chloride concentrations for the deep monitor well were obtained when using the model during the injection and recovery phases of cycle 1, but not for the injection well during the recovery phase of cycle 1 even after several attempts. This precluded the determination of the recovery efficiency values by using the model. The unsatisfactory comparisons of simulated to observed dimensionless chloride concentrations for the injection well and failure of the model to represent the field data at this well could be due to the characteristics of the Lower Floridan aquifer (at the local scale), which is cavernous or conduit in nature. To test this possibility, Reynolds numbers were estimated at varying distances from the injection well, taking into consideration two aquifer types or conceptual systems, porous media and cavernous. For the porous media conceptual system, the Reynolds numbers were greater than 10 at distances less than 1.42 meters from the injection well. Thus, application of Darcy's law to ground-water flow might not be valid at this distance. However, at the deep monitor well (171 meters from the injection well), the Reynolds number was 0.08 which is indicative of laminar porous media flow. For the cavernous conceptual system, the Reynolds numbers were greater than 2,000 at distances less than 1,000 meters from the well. This number represents the upper limit of laminar flow, which is the fundamental assumption

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USGS1996

Reconnaissance of water quality at four swine farms in Jackson County, Florida, 1993

The quality of ground water on four typical swine farms in Jackson County, Florida, was studied by analyzing water samples from wastewater lagoons, monitoring wells, and supply wells. Water samples were collected quarterly for 1 year and analyzed for the following dissolved species: nitrate, nitrite, ammonium nitrogen, phosphorus, potassium, sulfate, chloride, calcium, magnesium, fluoride, total ammonium plus organic nitrogen, total phosphorus, alkalinity, carbonate, and bicarbonate. Additionally, the following field constituents were determined in the water samples: temperature, specific conductance, pH, dissolved oxygen, and fecal streptococcus and fecal coliform bacteria. Chemical changes in swine waste as it leaches and migrates through the saturated zone were examined by comparing median values and ranges of water- quality data from farm wastewater in lagoons, shallow pond, shallow monitoring wells, and deeper farm supply wells. The effects of hydrogeologic settings and swine farmland uses on shallow ground-water quality were examined by comparing the shallow ground-water-quality data set with the results of the chemical analyses of water from the Upper Floridan aquifer, and to land uses adjacent to the monitoring wells. Substantial differences occur between the quality of diluted swine waste in the wastewater lagoons, and that of the water quality found in the shallow pond, and the ground water frm all but two of the monitoring wells of the four swine farms. The liquid from the wastewater lagoons and ground water from two wells adjacent to and down the regional gradient from a lagoon on one site, have relatively high values for the following properties and constituents: specific conductance, dissolved ammonia nitrogen, dissolved potassium, and dissolved chloride. Ground water from all other monitoring wells and farm supply wells and the surface water pond, have relatively much lower values for the same properties and constituents. To determine the relation between land uses and ground-water quality on the four swine farms, ground-water-quality data were divided according to the following land uses: confined operations in which swine are kept in houses and not allowed to roam freely, and unconfined operations in which swine are allowed to roam freely in determined areas. Confined operations had lagoons to receive the diluted swine wastes washed from the houses.

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USGS1996

Comparison of estimated and observed stormwater runoff for fifteen watersheds in west-central Florida, using five common design techniques

Hydrologists use several traditional techniques for estimating peak discharges and runoff volumes from ungaged watersheds. However, applying these techniques to watersheds in west-central Florida requires that empirical relationships be extrapolated beyond tested ranges. As a result there is some uncertainty as to their accuracy. Sixty-six storms in 15 west-central Florida watersheds were modeled using (1) the rational method, (2) the U.S. Geological Survey regional regression equations, (3) the Natural Resources Conservation Service (formerly the Soil Conservation Service) TR-20 model, (4) the Army Corps of Engineers HEC-1 model, and (5) the Environmental Protection Agency SWMM model. The watersheds ranged between fully developed urban and undeveloped natural watersheds. Peak discharges and runoff volumes were estimated using standard or recommended methods for determining input parameters. All model runs were uncalibrated and the selection of input parameters was not influenced by observed data. The rational method, only used to calculate peak discharges, overestimated 45 storms, underestimated 20 storms and estimated the same discharge for 1 storm. The mean estimation error for all storms indicates the method overestimates the peak discharges. Estimation errors were generally smaller in the urban watersheds and larger in the natural watersheds. The U.S. Geological Survey regression equations provide peak discharges for storms of specific recurrence intervals. Therefore, direct comparison with observed data was limited to sixteen observed storms that had precipitation equivalent to specific recurrence intervals. The mean estimation error for all storms indicates the method over estimates both peak discharges and runoff volumes. Estimation errors were smallest for the larger natural watersheds in Sarasota County, and largest for the small watersheds located in the eastern part of the study area. The Natural Resources Conservation Service TR-20 model, overestimated peak discharges for 45 storms and underestimated 21 storms, and overestimated runoff volumes for 44 storms and underestimated 22 storms. The mean estimation error for all storms modeled indicates that the model overestimates peak discharges and runoff volumes. The smaller estimation errors in both peak discharges and runoff volumes were for storms occurring in the urban watersheds, and the larger errors were for storms occurring in the natural watersheds. The HEC-1 model overestimated peak discharge rates for 55 storms and underestimated 11 storms. Runoff volumes were overestimated for 44 storms and underestimated for 22 storms using the Army Corps of Engineers HEC-1 model. The mean estimation error for all the storms modeled indicates that the model overestimates peak discharge rates and runoff volumes. Generally, the smaller estimation errors in peak discharges were for storms occurring in the urban watersheds, and the larger errors were for storms occurring in the natural watersheds. Estimation errors in runoff volumes; however, were smallest for the 3 natural watersheds located in the southernmost part of Sarasota County. The Environmental Protection Agency Storm Water Management model produced similar peak discharges and runoff volumes when using both the Green-Ampt and Horton infiltration methods. Estimated peak discharge and runoff volume data calculated with the Horton method was only slightly higher than those calculated with the Green-Ampt method. The mean estimation error for all the storms modeled indicates the model using the Green-Ampt infiltration method overestimates peak discharges and slightly underestimates runoff volumes. Using the Horton infiltration method, the model overestimates both peak discharges and runoff volumes. The smaller estimation errors in both peak discharges and runoff volumes were for storms occurring in the five natural watersheds in Sarasota County with the least amount of impervious cover and the lowest slopes. The largest errors were for storms occurring in the three small natural watersheds in the eastern part of the study area. The mean estimation errors for peak discharge ranged from an underestimation of 63 percent to an overestimation of 224 percent. For runoff volume, the mean estimation errors range from an underestimation of 63.3 percent to an overestimation of 267 percent.

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