Technical reports

The report presents the district’s minimum flows and levels (MFLs) reevaluation for Lake Colby, which includes a schedule for the establishment and reevaluation of MFLs under Florida law.

The report presents the district’s minimum flows and levels (MFLs) reevaluation for Three Island Lakes, which includes a schedule for the establishment and reevaluation of MFLs under Florida law.

The report presents the district’s minimum flows and levels (MFLs) reevaluation for Lake Grandin, which includes a schedule for the establishment and reevaluation of MFLs under Florida law.

The report documents the St. Johns River Water Management District’s adopted minimum levels for the St. Johns River at State Road 50, in Orange and Brevard counties.

The report documents the St. Johns River Water Management District’s adopted minimum levels for Lake Monroe.

This report identifies future water supply needs, and areas where those needs cannot be met by the water supply plans of major water users without unacceptable impacts to water resources and related natural systems (which are priority water resource caution areas).

This plan identifies water supply development project options and water resource development projects that will meet future water supply needs while sustaining water quality and protecting wetland and aquatic systems. Addendum DWSP 2005-A reflects changes to tables 13, 14 and 15, and fiqures 5 and 6 of the district Water Supply Plan 2005. Addendum DWSP 2005-B reflects changes to the Ormond Beach Water Treatment Plant Expansion Project. Addendum DWSP 2005-C includes 24 newly identified projects and one project has been reclassified as multijurisdictional. Figures 5 and 6 of the district Water Supply Plan 2005 have been modified to reflect these updates. Tables 13, 14, and 15 have also been updated. Addendum DWSP 2005-D adds an expanded description of the role of water conservation and the use of reclaimed water in meeting projected water demands, removes four water supply development projects, identifies 16 completed water supply development projects, and refines the descriptions of water supply development projects.

This report includes the location of individual springs, their physical description and, when available, a picture of the spring and spring area, tabulations of spring flow and quality, and historical trends in discharge and concentrations of chloride, sulfate, and total nitrogen.

This report documents how a regional groundwater flow model was used to simulate changes in water levels and flow rates between the average 1995 model calibrations and the 2020 projections.

This document presents minimum flows and levels (MFLs) for the St. Johns River at State Road 44 near Deland, Fla., to identify flows and levels below which harm would occur to the aquatic ecosystems along the river. Establishment of MFLs is required by Florida law.

Ambient water quality data for a variety of water body sampling sites within the St. Johns River Water Management District were compiled and analyzed to evaluate status and trends. This report documents the analysis of the data.

The St. Johns River Water Management District (SJRWMD) performed the water allocation study reported in this document in response to a directive from the 1994 Florida Legislature. The information contained in this document describes the methods and assumptions; the data; the evaluation and results of the effects of the consumptive use withdrawals on groundwater, surface water, and the aquatic and wetland communities; and the recommendations for the Ocklawaha River Basin. The availability of water from the lower Ocklawaha River subbasin for human consumption was also evaluated.

Due to increasing demands on water supplies, legislation in the state provides for future water supply planning programs. As part of the work to find alternative sources of potable water and to optimally distribute the water resources available today to east-central Florida, the district designed two models — a deficit model and a decision model — to assist in decision-making. This report documents those models.

This is the first annual report that examines the status and trends of water quality for water bodies of regional significance in the Middle St. Johns River Basin.

This report describes and documents the development of the models used in assessing minimum flows and levels (MFLs) for the middle St. Johns River (MSJR). Also included in this report are five examples of hypothetical MSJR surface water withdrawal alternatives as they relate to MFLs.

This study assesses ambient water quality data for a variety of water body sampling sites within the St. Johns River Water Management District for the purpose of characterizing the current status of and trends in water quality for water bodies districtwide.

This report provides documentation and instruction for a user-written computer program designed to determine temporal trends in water quality data and their magnitudes.

The upper Ocklawaha River basin was selected for one of five Surface Water Improvement and Management programs within the St. Johns River Water Management District. This report develops revised pollutant load reduction goals for phosphorus for the seven major lakes in the basin: Beauclair, Dora, Harris, Little Harris, Eustis, Griffin, Yale, and Weir.

The purpose of this report is to outline a long-term plan for monitoring plant communities in the Upper St. Johns River Basin using remote sensing. A standard vegetation classification scheme is provided, with photographs, for 32 defined categories.

Seventeen springs (three of which are submerged) in the St. Johns River Water Management District were sampled to assess water quality and stable and radioactive isotope concentrations. The purposes of the sampling were (1) to document water quality, (2) to determine the isotopic characteristics of spring water, (3) to determine the age of spring water and to evaluate the nature of the springflow system, and (4) to determine the source of nitrogen in springs with nitrate-nitrogen concentrations above 0.2 milligrams per liter.

The primary objective of the study was to construct a regional model to investigate saltwater intrusion into the freshwater zone of the Floridan aquifer system of northeast Florida in response to groundwater withdrawals. Another objective was to evaluate strategies for reducing the potential for saltwater intrusion within the Floridan aquifer system of the study area. A third objective was to ascertain relative levels of stress on the freshwater/saltwater interface at various well locations.

The study methodology consisted primarily of the development and use of a finite-element, multi-aquifer, sharp-interface groundwater flow model. The model code used was SIMLAS (saltwater-intrusion model for layered aquifer systems).

This report evaluates existing water quality data about current water quality conditions in the Upper Floridan aquifer as the basis for designing a monitoring network to assess groundwater quality conditions. Available water quality data are used to assess groundwater resources on regional and subregional scales, detect long-term trends, and identify potential problem areas.

This report identifies changes in nitrate concentrations in Wekiwa Springs from 1961 to 1999. Fifty sites were sampled in the Wekiva groundwater basin for nitrate nitrogen and 11 sites for isotopes. Land use changes between 1973 and 1990 suggest that the sources for the nitrate at Wekiwa Springs are inorganic fertilizers and septic tanks. The water was also age-dated.

A numerical groundwater flow model was developed for the east-central Florida region that is a revision and expansion of several previous regional models that cover the area. The model was calibrated to average, steady-state 1995 hydrologic conditions. The model was also calibrated in a qualitative fashion to estimated predevelopment conditions by comparing simulated water levels and spring flows to available estimates. The calibrated model was used to predict the potential changes to average surficial aquifer system and Floridan aquifer system water levels, and to average springflow rates as a result of projected 2020 magnitudes and locations of Floridan aquifer system withdrawals.

This report includes the location of individual springs, their physical description and, when available, a picture of the spring and spring area, tabulations of spring flow and quality, and historical trends in discharge and concentrations of chloride, sulfate, and total nitrogen.

Rodents were trapped as part of an effort to determine the reasons for their numbers in and around the Lake Apopka restoration area.

As part of its water supply planning and management program, the St. Johns River Water Management District studied elevations in the intermediate aquifer to determine areal distribution and leakance from the confining layer.

Twenty-nine project areas, covering 313,000 acres of public land, were surveyed to determine the abundance of wildlife as a tool for managing the public land.

This study evaluated the overall effectiveness of the St. Johns River Water Management District’s groundwater level monitoring network. The study examined the purpose and objectives for the network, the completeness of knowledge concerning well construction and well use, the areal coverage and temporal suitability of the measurements, and the spatial effectiveness of the network.

This study investigated the technical feasibility and hydrologic impacts of artificial recharge with reclaimed wastewater through rapid infiltration basins into the groundwater system.

The Floridan aquifer system of northeast Florida was simulated using a regional, numerical drawdown model — a type of groundwater model in which changes in water levels, as opposed to absolute water levels, are determined in response to changes in well-withdrawal rates.

Geostatistics provides a framework for the analysis, characterization, and estimation of spatial data. A geostatistical analysis was undertaken to assess regional chloride conditions in the Upper Floridan aquifer. This analysis was based on data from the current water quality monitoring network in the DeLand groundwater basin. The analysis was undertaken as a means of devising a more efficient monitoring network for this area.

Water quality and stable and radioactive isotope concentrations were determined for selected springs. Seventeen springs (two of which are submerged), eight wells in the Upper Floridan aquifer, and one well in the Lower Floridan aquifer were sampled (1) to document water quality, (2) to determine the isotopic characteristics of spring water, (3) to determine the source of spring water, (4) to determine the age of spring water and to evaluate the nature of the spring flow system, and (5) to determine the sources of elevated nitrate-nitrogen concentrations in these springs.

Water use data were collected by county and compiled by category of use. Water use covers all water withdrawals from groundwater or surface water sources. The appendix presents specific data for each county.

The purpose of the study was to compare, on a regional basis, future water supply needs with the possible sources of fresh groundwater from the Floridan aquifer system.

This assessment defines the limits of water resource impacts beyond which a water resource-related problem could occur, projects the water resource impacts that could occur in 2020 as a result of projected changes in water use, and identifies priority water resource caution areas.

A flood protection and environmental enhancement plan for the Upper St. Johns River Basin includes creation of marsh conservation areas and water management areas. One marsh conservation area will be created from Melbourne-Tillman Water Control District (MTWCD) land. Removal of this land will remove runoff area and reduce surface water storage. This report presents the development of two models to simulate the hydrology and hydraulics of the MTWCD that are needed to evaluate various planned activities for the MTWCD.

This report documents the current districtwide drainage basin data layer. Maps depict the basin boundaries, and tables list descriptive information.

The primary objective of this study was to predict changes in hydraulic-head levels in the Floridan aquifer system of the study area that will occur in response to projected increases in groundwater withdrawals between 1985 and 2010. Another objective was to enhance the understanding of interactions that occur between the aquifers within the Floridan aquifer system and between the Floridan aquifer system and the overlying surficial aquifer system. A further objective was to improve estimates of the hydraulic properties of the Floridan aquifer system and of the overlying upper confining unit.

A groundwater flow model was developed for the Volusia groundwater basin, an area in which water resource problems have become critical or are projected to become critical by the year 2010. The model was used to perform predictive simulations for the year 2010.

Water use data were collected by county and compiled by category of use. Water use covers all water withdrawals from groundwater or surface water sources. The appendix presents specific data for each county.

Water use data were collected by county and compiled by category of use. Water use covers all water withdrawals from groundwater or surface water sources. The appendix presents specific data for each county.

The SURFDOWN and MODFLOW models are used iteratively to determine the drawdowns in the water table of an unconfined aquifer and to adjust the drawdowns in the elevation of the potentiometric surface of a confined aquifer.

Water use data were collected by county and compiled by category of use. Water use covers all water withdrawals from groundwater or surface water sources. The appendix presents specific data for each county.

The purpose of the Benchmark Farms project is to collect field-measured data to evaluate crop-specific water use, monitoring a network of sites on representative properties of agricultural water users. Information in this report provides an overall view of crop irrigation requirements and an estimate of the water withdrawn for leatherleaf fern and potatoes during the 5-year period 1990-94.

Urban runoff entering stormwater ponds contains a significant amount of heavy metals, which concentrate in the pond sediments. This study was conducted to determine whether fish that live in stormwater treatment ponds accumulate significant concentrations of heavy metals — which can then be transferred up the food chain — and whether fish that forage in different manners bioaccumulate heavy metals in different concentrations.

Water use data were collected and compiled by category of use. Water use covers all water withdrawals from groundwater or surface water sources. The appendix presents specific data for each county.

This pilot study was conducted to determine if recharge rates derived by using radioactive isotopes to age-date groundwater are accurate enough to be used in other areas of the St. Johns River Water Management District where hydrogeologic data are not available. Five sites were selected for study, one in Clay County and four in Volusia County.

This report describes the current hydrology of the Upper Orange Creek Basin and some hydrologic analyses. Water resources concerns are identified in order to initiate the development of an effective water management plan for the entire Orange Creek Basin.

Due to the tenuous nature of the groundwater resources and to the growth of the city of Titusville, northern Brevard County was identified as an area where available groundwater supplies may not be adequate to fulfill projected needs for those resources. Therefore, the St. Johns River Water Management District developed a regional groundwater flow model of the groundwater resources in the area as part of its Water Supply Needs and Sources Assessment.

Water quality in the upper Ocklawaha River Basin has been degraded by nutrient loading from agricultural and urban development. Several of the lakes in the basin are among the most eutrophic in the state, whereas others are in the less productive mesotrophic category but are potentially threatened by increasing urban development. The purposes of the study were to develop (1) preliminary nutrient budgets for the years 1980-90 for the seven major lakes in the basin and (2) recommendations for further studies and management actions to improve water quality.

This inventory includes data for 221 wastewater treatment plants with permitted capacities of 0.1 million gallons per day or greater and located within the St. Johns River Water Management District (SJRWMD) or outside but within counties partially under SJRWMD jurisdiction. Information may be used to identify sources of treated wastewater for potential reuse.

A geographic information system model was developed to estimate the likelihood of harm to native plant communities from groundwater withdrawals. The model was developed using soil permeabilities, sensitivities of plant communities to dewatering, and projected declines in the water table of the surficial aquifer system. The results of the model highlight those areas having the highest likelihood of harm to native vegetation from proposed groundwater withdrawals.

The reconnaissance reports compile information and make recommendations to help resource managers identify priority needs for research into and management of the Lower St. Johns River Basin. This volume examines and evaluates the extent of present knowledge regarding the volume and movement of the waters, salinity, and past efforts to simulate the flow of the lower St. Johns River, and it shows where gaps in knowledge of river dynamics exist. Described are water elevations, flows, the dominant forcing factors (such as tide and wind), salinity, and the physical and computer models that have been developed to describe these factors. A brief review of water quality models is included.