The Journey of Water
To understand Florida's springs and their importance as natural resources, we must first understand the water cycle and aquifer that sustains them.
Getting to the Source of Springs
Contrary to popular belief, Florida's springs are not the source of freshwater; they are but one step on water's long journey through what is known as the Floridan Aquifer, our underground water source. Learn about the water cycle and the flow of water through the aquifer to gain a better understanding of Florida's springs. Also, learn more about how humans impact the quality and quantity of water in the aquifer and ultimately in the springs.
The information below is derived from the Interactive Journey of Water.
Water Cycles Around
The journey of water begins in the sky, where the state's abundant rainfall recharges the Floridan aquifer, our underground water source. Read below to learn about the water cycle and how it contributes to spring formation.
Rainfall is a function of various atmospheric and physical factors, and the most important of these are gravity and humidity. As the tiny water droplets within a cloud merge together into larger, heavier drops, they eventually overwhelm the relative level of atmospheric humidity that keeps them airborne. Relative humidity is a measurement of the amount of water the air can hold at a given temperature. Scientists have recently determined that once these drops reach a diameter of twenty millimeters, rain will begin to fall. Every day, over 150 billion gallons of rain falls in Florida, more than any other state in the nation except Louisiana.
Evaporation and Condensation
Water's journey through the water cycle begins with a process called evaporation whereby water stored in surface bodies of water like lakes, rivers and the ocean is converted into water vapor by the heat of the sun. Convection then draws this warmer, wetter air upwards where it comes into contact with cooler, high atmospheric air and eventually condenses back into tiny water droplets. Collectively, these tiny droplets are called clouds.
In addition to evaporation, a significant percentage of the water is released into the atmosphere by trees and plants in a process called transpiration. In order to facilitate photosynthesis, plants absorb water from the soil through their roots, a process that can also clean water by filtering out nutrients and pollution. They then transpire this water back into the atmosphere through their leaves and stems. About 70 percent of all rainfall returns to the atmosphere in the form of evaporation and transpiration.
Rainfall that is not absorbed directly into the soil, through the roots and leaves of plants, or accumulated into existing bodies of water such as lakes or rivers is called surface, or stormwater runoff. In areas where the underlying geologic formation is impervious to water, as in the case of clay, runoff is a natural process, directing water in sheet flow, into lakes, rivers, wetlands, and the ocean. In Florida, where loose sandy soils and porous limestone bedrock are common, rainfall that reaches the surface of the earth usually soaks directly into the ground.
Rainfall seeps underground through a process called percolation, whereby water travels downwards through the tiny spaces between rocks and soil particles, and within the "Swiss cheese" structure of the limestone. The water eventually saturates the underlying limestone in much the same way water fills the tiny holes of a sponge. It is this process of percolation that allows Florida's abundant rainfall to replenish the immense volumes of water flowing from the springs.
Rain Falls Again
Though the first step of water's journey to the springs begins in the sky, the water cycle itself is a never-ending process, and no single step is more important than any other. Evaporation, transpiration, condensation, rainfall, run-off, and percolation all play a critical part in ensuring that water is consistently available for both natural processes and human use.
From Aquifer to Spring
The source of our drinking water and the crystal clear water in springs is the Floridan Aquifer, nature's underground water storage system. Read below to learn about our underground water cooler.
Water begins its journey underground to the aquifer by a process known as recharge whereby rainfall seeps underground to infiltrate the limestone below. The overall land surface area where water seeps underground and contributes rainwater to a specific spring is called a spring's recharge basin. North-central Florida, where spring upwellings are most abundant, contains hundreds of recharge basins. Given their complex three-dimensional structure, recharge basins are determined through extensive scientific studies of local subsurface geology and groundwater flow.
Percolation is the physical process by which rainwater falling within a given recharge basin slowly travels underground through the tiny spaces between rocks and soil particles. Florida's unconsolidated, sandy soils as well as the porous nature of the limestone aquifer itself provide the ideal conditions for unrestricted percolation. Yet, depending on the type of soil and the depth of the limestone aquifer, some areas allow water to percolate water underground faster than others, resulting in different recharge rates. Areas of high recharge occur in only 15 percent of the state, mostly in the sandy highlands of west and west-central Florida.
Speleogenesis is a big word that describes the formation of caves. In Florida, speleogenesis occurs underground through a simple chemical reaction. As rainwater falls through the atmosphere and percolates through the soil, it combines with carbon dioxide in the air and decaying vegetation to form a mild carbonic acid that slowly dissolves the limestone enlarging small cracks and pores. Over thousands of years, these small pores and cracks expand to become underground caves and caverns. Collectively, these interconnected caves are the pipes through which groundwater flows within the aquifer to the springs.
Gravity is the major force in groundwater movement in the aquifer. Under natural conditions, groundwater moves "downhill" until it reaches the land surface at a spring or through a seep in a riverbed, lake or wetland. The speed with which water flows through the aquifer is also dependent upon the porosity and permeability of the limestone. In other words, water flows more quickly if the spaces or holes in the limestone are larger and if these spaces are closely connected to allow water to flow through.
Sinkholes are depressions in the land caused by dissolution of the limestone near the surface or the collapse of an underground cave. Once these "windows" to the aquifer are open, they may provide direct access to the conduits through which water flows from the recharge basin to the springs themselves. As a result, they are one of the most common points of entry for cave divers seeking to explore and study the underground aquifer.
Springs form where groundwater is forced up and onto the surface through openings in the ground. This is caused by the differences in the slope or "hydraulic gradient" in the aquifer. As rain falls and percolates underground, it exerts pressure on the water already in the aquifer, forcing some to the surface through natural openings. The highest concentration of springs in Florida lies in the north-central part of the state where the aquifer is closest to the surface. Springs are classified or categorized based on the amount water discharge. The largest springs like Wakulla and Silver Springs are classified as "magnitude 1" springs which means they each discharges more than 65 million gallons of water a day - the equivalent of about 1.3 million bathtubs full!
The volume of water flowing from a spring is dependent upon a variety of factors: the water pressure in the aquifer beneath it, the number of caves leading to the spring vent or opening, and the size of the vent itself. Florida's springs are the largest by volume in the world, giving birth to and supporting entire river eco-systems like the Suwannee and the Santa Fe. Collectively, Florida's springs discharge over 19 billion gallons of freshwater each day.
Every day in Florida, more than 7 billion gallons of water are consumed, most of it withdrawn from the aquifer. In addition, harmful fertilizers, chemical pesticides and other pollutants that are introduced to the land make their way into our groundwater supply and eventually the springs.
Read below to learn about the threats to the aquifer and springs.
Landscaping and Lawn Care
Certain methods of lawn care and landscaping can have a detrimental impact on Florida's aquifer and springs because they require frequent applications of chemical fertilizers and pesticides. These chemicals introduce toxins and nitrates into the aquifer, polluting our drinking water, contributing to nuisance algae growth, and endangering wildlife species in the springs.
Conventional landscaping and residential lawn care also consume large amounts of water due to the need for regular irrigation. Nearly fifty percent of all water withdrawn for public supply is used solely to water residential lawns-an estimated 900 million gallons a day.
Row Crop Agriculture
Agriculture impacts both the quality and quantity of water flowing underground. Every year, millions of tons of fertilizers and pesticides are applied to crop fields, a significant percentage of which ends up leeching into the aquifer. Like chemicals used in residential landscaping, these fertilizers and pesticides can have a significant impact on springs as well as our drinking water.
Crops also consume large quantities of water removed from the aquifer - more than 1.5 billion gallons of water each day. A single center-point irrigation system on a typical Florida farm may use over one million gallons of water per day.
Large livestock farms can have a direct impact on both the quality and quantity of underground water. Large quantities of animal wastes can enter the aquifer through surface streams, sinkholes, and swallet holes as well as percolate through Florida's porous soils.
Weeks, months, and sometimes even years later, these contaminants end up in our drinking water and in the springs where we swim. Livestock also consume large quantities of water in addition to feed that must be grown with irrigated water drawn from the aquifer.
Sprawl and Development
Since 1950, Florida's population has grown four-fold. The rate of increase shows no sign of leveling off; even today, 750 new residents move into the state each day. This rapid increase in population has led to development and sprawl in rural areas that were once dominated by forests and farms.
The resulting changes in land use have had a dramatic effect on the health of the recharge basins for many springs. Demands for residential water, increasing stormwater runoff and intensifying direct human impact at the springs have all contributed to the decline in their conditions.
Runoff and Stormwater
An average of 150 billion gallons of rain falls each day in Florida. Where this water is not soaked into the soil, absorbed by plants, or gathered into existing bodies of water, it is diverted from parking lots, roads and highways to reduce the risk of flooding. The process is called stormwater management. However, once diverted, stormwater and everything it carries with it does not go out of our lives. Stormwater washes heavy metals, petroleum by-products, pet wastes, and toxins from the land unfiltered through a complex system culverts, drainage ditches, and retention ponds. Some of these pollutants wash into rivers and streams and percolate into the aquifer and our drinking water.
Golf Courses and Athletic Fields
Recreational sports like golf and football are a way of life in Florida. Yet, they have unseen, detrimental impacts on the aquifer. Golf courses and athletic fields often require specialized strains of grass that demand excessive irrigation, fertilization, and pesticide use. With regular rainfall, these chemicals leech through the root systems and soil, and eventually into the aquifer.
The development of golf courses and athletic fields in areas previously covered with native forest can also have a negative impact on the recharge basins of springs by increasing surface runoff, soil erosion, and direct human impacts.
Human Consumption and Overuse
Every day in Florida, over 7.2 billion gallons of freshwater are consumed directly by humans to satisfy the demands of agriculture, industry, power plants, development, and municipal and public water supplies. On average, each Florida resident uses about 103 gallons of water per day. More than 60 percent of this water is pumped directly from deep underground aquifers. That's about four billion gallons, enough to fill the Gator Bowl nearly full daily for a year!
As a result, we are withdrawing water from Florida's underground aquifer faster than it can be replenished, decreasing flow levels at many head springs, stressing sensitive spring plant and animal species, and causing permanent, long-term damage to the geologic structure of the aquifer itself.
Sinkholes are formed when the limestone above a conduit or cave in the aquifer collapses. They may form over many years or may form suddenly as a result of too much water being drawn from the aquifer and from natural causes. The sinkhole may or may not be filled with water but almost always feeds directly into the aquifer below. In many cases, residents have dumped debris ranging from construction materials, garbage, refrigerators, automobiles and chemicals. Dumping anything into sinkholes can seriously impact the aquifer and water supply.
Recreational activities like camping, swimming, tubing, and boating can have a direct impact on the water quality of the springs as well as the animals and plants that live there. These impacts include the trampling of native vegetation, the disturbance of wildlife, an increase in soil erosion, and direct physical damage to plants and animals by boat props, groundings and anchors. Trash left behind at the springs not only introduces pollutants, but also destroys the natural look and atmosphere of the spring's environment.