The climate of Florida varies slightly from the northern panhandle area to southern Florida, but in general is characterized by a relatively high mean annual temperature and rainfall, and is humid and subtropical. Average annual rainfall in Florida can range from about 40 inches in the western Keys to more than 60 inches in the panhandle. Severe weather generally comes in the form of intensive thunderstorm activity in the summer months, tornadoes, tropical storms, and hurricanes. In recent years, weather extremes appear to be intensifying, from drought-like conditions during spring months to more active hurricane seasons.

Water resources are one of Florida's most valued assets. The State has more than 1,700 streams and rivers, 7,800 freshwater lakes, including Lake Okeechobee (one of the largest lakes in the United States after the Great Lakes), and is underlain virtually everywhere by aquifers capable of yielding significant quantities of freshwater to wells (fig. 2). The State has about 320 springs, whose combined discharge is estimated at over 8 billion gallons per day, and has 27 of the 78 first-magnitude springs (discharge greater than 100 cubic feet per second) in the United States (figure 3 and figure 4).

Although Florida's water resources are extensive, they are finite, and growth in population, tourism, industry, and agriculture is placing an increasing demand on them. Satisfying the demands of all water users is perhaps Florida's greatest resource challenge.

North Florida has some of the largest rivers in the State as well as a number of important streams, lakes, springs, and estuaries. In terms of annual discharge, the area has three of the five largest rivers in the State: the Apalachicola, Choctawatchee, and Escambia. Many of the rivers in northwest Florida originate in Alabama and Georgia, and interstate water management relating to these rivers is an increasingly important issue.

Ground water is the primary source of water supply for northwest Florida. The four major ground water systems in northwest Florida include the surficial aquifer system (which includes the sand and gravel aquifer), the intermediate aquifer system, the Floridan aquifer system, and the Sub-Floridan system. Wellhead protection is particularly important in the westernmost parts of northwest Florida, where much of the population relies on the sand and gravel aquifer for water supply. This aquifer is close to the surface and is susceptible to contamination from surface activities. In the big bend area of the State (Suwannee River basin), most of the Floridan aquifer system is unconfined and also vulnerable to contamination from the surface (fig 5).

In central Florida, the St. Johns River is the dominant surface-water feature (fig. 6). The river was selected as one of the first of the American Heritage Rivers, because of its unique character and value to the residents of Florida. Other than the several tributaries to the St. Johns River, major river systems in central Florida include the Kissimmee River (the subject of current restoration efforts), and the Withlacoochee, Hillsborough, Manatee, and Peace Rivers. The central Florida landscape is noted for its many seepage lakes and springs. However, increasing urbanization has resulted in concerns over declining lake levels and spring discharge. Central and west-central Florida are underlain by the surficial aquifer system, the intermediate confining unit, and the Floridan aquifer system (including the Upper and Lower Floridan aquifers). The primary source of drinking water for central and west-central Florida is the Floridan aquifer system. Contamination of ground water is of great concern in central Florida because of the proximity of the surficial aquifer to land surface, land uses in the area (including phosphate mining), the lack of a confining layer in many areas, and the presence of breaches through the confining layer that provide direct conduits to underlying aquifers.

Figure 6. St. Johns River at Jacksonville, Florida, showing the Main Street Bridge. [larger image]

Water supply in west-central Florida is a critical issue, requiring the consideration of development of a variety of alternative sources including brackish water and submarine springs in the Gulf of Mexico. Northeast Florida is particularly vulnerable to saltwater intrusion because of a large population and consequent demands on ground-water resources. Water managers in northeast Florida and in west-central Florida are actively monitoring public supplies for increasing chloride content, and are developing alternative plans for water supplies for the future.

The southern part of the Florida peninsula contains a unique ecological landscape. One of the major hydrologic features of south Florida is Lake Okeechobee, which is the second largest freshwater body wholly contained within the continental United States. The entire natural system in south Florida lies on top of a limestone platform containing a complex sequence of aquifers (the Biscayne and Floridan aquifer systems). The Everglades is an irreplaceable wilderness that is bounded to the east by a highly developed urban corridor and to the west by a rapidly growing urban area. Along the periphery of the Florida peninsula in south Florida are beautiful beaches, highly productive bays, estuaries, mangrove forests, and extensive coral reefs. The hydrology of south Florida is unique in the State because of its highly manipulated character. About half of the original Everglades has been lost to urban, suburban, and agricultural uses through "reclamation" of the land using a complex series of drainage canals, levees, control structures, and pumps that have been constructed since the 1940's. The result is a hydrologic system that is directly controlled and managed to distribute freshwater in support of urban and agricultural activities. Reduced water availability to the Everglades and disruption of normal high and low water conditions have excessively stressed natural ecosystems with resulting large-scale reductions of terrestrial and aquatic wildlife communities. Additionally, nutrient-laden water from agricultural areas flowing through the greater Everglades has inexorably shifted the dominant vegetation from sawgrass to cattails in many areas with resulting disappearance of many species of natural fauna.

Figure 7. Population distribution in Florida. (From Marella, 1998, Water use and trends and demand projections in the Northwest Florida Water Management District: U.S. Geological Survey Open-File Report 98-269, 35 p.) [larger image]

Driving Forces

Florida's unique character, warm climate, abundant natural resources, and economic opportunities continue to attract many new residents, which increasingly stresses hydrologic systems (fig. 7). With development in the State comes increased demand for water and increased potential for degradation of natural systems. Fundamental to the wise stewardship of water resources in Florida is an understanding of watershed systems and processes. The definition of a watershed has been broadened to include not only the surface water drainage basin but the ground-water basin as well. The understanding of processes and interactions between ground water and surface water on a watershed-based scale forms the framework for answering complex questions and for allocation and protection of resources. To evaluate the entire watershed, cross-disciplinary integrated science is required to effectively evaluate physical, chemical, and biological processes.

Florida has experienced dramatic population growth since the middle of this century. It is the fourth most populated State in the United States and is expected to grow at a rate of three percent annually, with most of the growth concentrated in coastal areas where less freshwater is available. In 1950, the State's population of 2.77 million used about 2.9 billion gallons per day and by 1995, the State's 14 million people used 7.2 billion gallons of freshwater daily. In addition to the resident population in Florida, an estimated 41 million people visited the State in 1995. In 1995, Florida ranked fifth nationally in terms of total water use, eighth in water used for public supplies, and second to California in use of ground water for public supplies. Irrigation in Florida has expanded at such a rate that in 1995 Florida agricultural production ranked among the top ten states in the Nation, 13th in total water used for irrigation, and 10th in ground water used for irrigation (fig. 8).

Figure 8. Agricultural water use. [larger image]

Historically, ground water has supplied most of Florida's water needs, but increased demands have stressed this resource to its limit in many areas. As water needs increase, alternative sources of water and ways to store water are sought. Some alternative sources include surface water and desalination of brackish water. More recently, storage in and recovery of freshwater from aquifers has been successfully used in local areas of Florida and elsewhere, and is under further investigation as a viable alternative to above-ground surface water storage. This process is known as aquifer storage and recovery (ASR) (fig. 9). Florida also has large agricultural and industrial users of water resources competing for the finite water resources of Florida. The development and allocation of water resources is anticipated to continue to be of major concern in the immediate and long-term planning for the State.

Florida's natural resources and climate that attract new residents and visitors also contribute to its susceptibility to hydrologic hazards, including floods, droughts, hurricanes, thunderstorms, hailstorms, and lightning strikes (fig. 10). The USGS provides hydrologic data and studies that can improve the understanding of effects resulting from some of the hydrologic hazards common to the state. Activities associated with the hazards mission of the USGS include long-term monitoring and forecasting, real-time monitoring, and evaluation of effects after flooding events to provide valuable data that can be used to mitigate the impact of future events and aid in preparation of risk assessments.

The karstic terrain of the State makes the ground-water resources particularly vulnerable to contamination from surface activities. Changing land use, as a result of development, changes the characteristics of the quality of water recharging the aquifer or entering surface-water systems. Contaminants from industrial, commercial, agricultural, and residential land uses have the potential to enter surface and ground waters. Some constituents, such as nutrients, pesticides, and selected organic compounds, have been studied; others, including pharmaceuticals and endocrine disruptors, are beginning to receive increased attention as contaminants of concern to human and environmental health (even at very low concentrations). The potential for the presence of these contaminants in ground water and surface water represent a new area of data collection and investigation for the USGS in Florida.

Rather than evaluating point and nonpoint contaminant sources separately, the concept of integrated or total loading to receiving water bodies from both sources is being used in the State to realistically evaluate contaminant impacts and serve as a basis for regulation of these sources. Total Maximum Daily Loads (TMDLs) are being determined based on water-quality data and discharge data for rivers and streams and lakes in the State. These water bodies have been prioritized according to the degree of degradation of water quality, based on existing data.

The Florida of 150 years ago was a vastly different place from what it is today because of entrepreneurs who saw opportunity in the state and modified the landscape to accommodate their visions of the future. Through the 20th century large tracts of land were "reclaimed" through industrious civil engineering projects that created vastly different ecosystems than what was originally in place. The primary tool for overhauling the landscape was the digging of canals to connect lakes for navigation and to convert wetlands to land suitable for agriculture or other uses. Late in the 20th century, the value of the natural systems was recognized and plans were made to restore as many areas as possible to their natural conditions. The effort to restore ecosystem functions has now become a defined societal goal that has broad public support. The Everglades, the Kissimmee River Basin, and Lake Apopka are examples of current efforts in the State (figure 11 and figure 12). Preservation and restoration of ecological systems are important driving forces because of the close connection between ecological functions, hydrologic system characteristics, and human health.

U.S. Geological Survey Role and Capabilities

To provide the Nation with reliable, impartial information to describe and understand the Earth, the USGS mission supports water-related, geologic, biologic, land use, and mapping studies that contribute to the safety, health, and well-being of Florida's citizens. The work conducted to meet the goals of the science issues identified in this Science Plan is divided into three general categories: basic data collection, hydrologic investigations, and research. The USGS in Florida has the capability to conduct multidisciplinary work to address these science issues because of the availability of expertise in geologic, biologic, and water resources. In addition to the available personnel in the State, expertise is available nationally and can be called upon as needed for interdisciplinary investigations, training of local personnel, and development of new approaches and technology to address the complex science issues of the State.

Figure 13. U.S. Geological Survey employee servicing equipment on a tower in Volusia County, Florida, used to measure evapotranspiration (ET) from an area of pine forest. [larger image]

The USGS is the Department of the Interior's science agency; it is a multidisciplinary, non-regulatory, and non-advocacy agency, and it has an established, long-term presence throughout Florida. The Florida District has programs underway that include surface- and ground-water monitoring networks, investigative and research studies with local agencies, and parts of nationwide initiatives such as Place-Based Studies and National Water Quality Assessment (NAWQA) programs. In addition, the presence of large areas of public land administered by the National Park Service (NPS), Fish and Wildlife Service (FWS), State agencies, and Florida Water Management Districts offers opportunities for cooperative work between the Florida District and these agencies. Opportunities also exist to cooperate with Tribes and other agencies such as the Environmental Protection Agency (EPA), National Oceanographic and Atmospheric Administration (NOAA), U.S. Army Corps of Engineers (USACE), Florida Department of Environmental Protection (FDEP), Florida Department of Agriculture and Consumer Services (FDACS), other State agencies, and universities that are conducting research on or near public lands. Through the Federal-State Cooperative Water Program, the Florida District plays an active role in water-related geologic, biologic, land use and mapping issues in many parts of the State by providing reliable, timely and impartial information needed to understand and wisely manage water resources (fig. 13).

The need to understand systems and processes on a watershed scale is most closely linked to the USGS mission goal "to provide science for a changing world in response to present and anticipated needs to expand our understanding of environmental and natural resource issues on regional, national, and global scales and enhance predictive/forecast modeling capabilities." The multidisciplinary approach to watershed science that is necessary to evaluate natural systems introduces opportunities for collaborative efforts within the USGS and with partners in the State.

The USGS is uniquely qualified to evaluate the effects of development, both past and present, on ecosystems, because of the breadth of experience available from all the programs of the USGS. The ongoing ecosystem restoration work in the Florida Everglades (a "Place-Based Study") has involved individuals from all the USGS programs (water, geology, biology, and mapping) and is a model for future collaborative studies. Other natural systems, where restoration is planned or is already underway (such as the Kissimmee River), offer additional opportunities for collaborative work.

Acknowledgments

The Florida Science Plan Team extends appreciation to Teresa Embry, Ron Spencer, and Jim Tomberlin of the Florida Scientific Reports Production Unit for their work on this report and visual presentation.

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:
°C=(°F-32)/1.8.

Sea level: In this report, sea level refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)--a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD of 1927).

Additional information about water resources in Florida is available on the Internet at http://fl.water.usgs.gov