Science

The noun “science” refers to two human endeavors:  (1) the knowledge of how natural and physical phenomena function, and (2) the systematic study that includes observing and experimenting with natural and physical phenomena.

As with any human endeavor, science can be extremely useful—think of the lives saved by the development of antibiotics, for example—but it can also be imperfect. Simply by choosing which aspects of a scientific problem to measure or examine can determine or even change the results of a scientific study. This phenomenon, known as the “Observer Effect,” is demonstrated especially in quantum physics but holds true in other fields of science as well.

In considering Florida’s water problems and the problems facing the Ichetucknee River System, we do well to consider science; we also do well to remember its limitations.

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Blue Hole/Window Into the Aquifer
Photograph by Wes Skiles

The Floridan Aquifer

The Ichetucknee River System is a window into the massive underground water feature called the Floridan Aquifer, one of the most productive aquifers in the world. Over 100,000 square miles in area, this “Southeastern Conference (SEC) of aquifers” underlies all of Florida and parts of southern Alabama, southeastern Georgia, southern South Carolina and a small part of southeastern Mississippi.

Here in North Florida, the Floridan Aquifer supplies our drinking water; it also supplies the drinking water for the cities of Daytona Beach, Gainesville, Tampa, Jacksonville, Ocala, Orlando, St. Petersburg and Tallahassee, among others.

Another significant feature of the Floridan Aquifer is that the weight of its freshwater keeps the layer of saltwater underneath it from entering our wells and municipal water supplies.

The Floridan Aquifer is renewable, fed by rainfall that percolates down through limestone rock to enter the underground caverns and rivers that lie beneath our feet. That rainfall, in turn, is fed by the evaporation of water from wetlands and the transpiration that occurs during plant photosynthesis; together, these two processes are called evapotranspiration.

 

Karst Landscape

Springs such as the Ichetucknee occur in what is called karst topography, a landscape characterized by caves, sinkholes, fissures, and other openings that are formed when rainfall dissolves limestone. In places where the Floridan Aquifer is high enough and where the underlying water pressure is strong enough, water is forced up from the aquifer through these openings to emerge from underground as springs and rivers.

At certain times in some places, we may observe the reverse of this process when water from the surface disappears underground. Features such as sinkholes and swallets can “swallow” surface water; there is a great example of this at O’Leno State Park, where the Santa Fe River disappears underground and emerges a few miles later at River Rise. During floods when rivers are high, springs can back up with river water and reverse flow in a process known as an estavelle, during which river water descends from the spring vent into the aquifer.

Sinkholes, which are characteristics of karst landscapes that can form slowly or suddenly, are increasingly problematic in Florida where they have claimed lives and property. Sinkhole damage, often caused in part by lowered levels of the Floridan Aquifer, can reduce property values and cause homeowners’ insurance rates to rise.

 

The Ichetucknee Trace

Many years ago, the Ichetucknee River flowed from its headwaters at Alligator Lake in Lake City to the Santa Fe River. We can see evidence of this portion of the river in the relict stream channel called the Ichetucknee Trace that runs north and east of Ichetucknee Springs. This dry valley, dotted with swallets and sinkholes, marks a major underground conduit that supplies Ichetucknee springs with water.

 

Springs:  Canaries in a Coal Mine

The Ichetucknee River System, as well as the other springs and spring-fed rivers and lakes in Florida, are our “canaries in a coal mine” because they offer us early warnings of problems with the Floridan Aquifer.

Nitrate pollution, which may cause health problems in people and animals, is visible in our waters as algae growth. Reduced spring flows may indicate that the level of the Floridan Aquifer is dropping, which can lead to increasing intrusion of saltwater into wells and municipal water supplies. For every foot that the Floridan Aquifer drops, the underlying layer of saltwater rises 40 feet.

Because we depend upon the Floridan Aquifer for our clean drinking water, we ignore these problems—problems that are visible and occurring now—at our own peril.

 

What the Ichetucknee Science Tells Us

Scientists have been studying Florida’s springs for decades. A little known but important fact of Florida history is that the science of systems ecology was born here with the biologist Howard T. Odum’s study of Silver Springs in the 1950s, the first analysis of a natural ecosystem that was ever conducted.

The Ichetucknee Springs & River Restoration Action Plan was prepared under the direction of Dr. Robert L. Knight, one of Odum’s students. The plan offers a useful summary of what we have learned from science about the Ichetucknee River System.

 

A Declining Aquifer Means Lower Spring Flows

Florida’s population began to mushroom in the late 1940s and early 1950s, as air conditioning became more available and returning World War II servicemen who had been stationed here moved their families into the state. Perhaps not coincidentally, some of the problems with Florida’s water began to register in the hydrological data that was gathered in the mid-20th century.

At the U.S. Highway 27 stream gauging station, the long-term median flow of the Ichetucknee River for 1917-2011 was 347 cubic feet per second (cfs) or 224 million gallons a day (MGD). Scientific analysis of this data indicates that spring flows started declining as early as the 1970s. According to the United States Geological Survey, the Ichetucknee River has lost approximately 25% of its flow since 1900. Scientific analyses of the data indicate that this loss is attributed to causes other than declining rainfall.

Average water withdrawals within the Ichetucknee Springshed have increased 132% since the 1960s. There are now more than 26,000 active groundwater consumptive use permits (CUPs) in North Central Florida that pump water from the same Floridan Aquifer that feeds groundwater to the Ichetucknee. The 2010 estimated pumping from those large wells is more than 4025 cfs or 2.6 billion gallons per day (BGD). In addition to the larger wells with CUPs, there are hundreds of thousands of smaller private supply wells throughout North Central Florida and Southeast Georgia that are collectively lowering the level of groundwater in the Floridan Aquifer.

As early as 1940, high rates of groundwater pumping in Northeast Florida and South Georgia resulted in significant declines in the level of groundwater in the Floridan Aquifer. These changes resulted in reduction of the area of the groundwater basin that feeds the entire Suwannee River, including the Ichetucknee Springshed. Groundwater that historically flowed toward the Ichetucknee and the Santa Fe and Suwannee rivers now flows toward the high pumping areas of Northeast Florida and South Georgia. In 2005, the aquifer recharge area for all of the springs in the Suwannee River Water Management District, including Ichetucknee, was estimated to have lost about 1900 square miles in area and 190 cfs (123 MGD) of flow.

Although the freshwater portion of the Floridan Aquifer is hundreds of feet thick, a change in groundwater levels of only a few feet in the vicinity of Ichetucknee Springs can result in a significant reduction in flow. When groundwater pumping is excessive, springs can stop flowing altogether, as demonstrated at White Springs in North Florida and Kissengen Springs in Central Florida.

An estimated 35% of the observed flow reduction in Ichetucknee Springs is caused by groundwater pumping within the Ichetucknee Springshed, while 65% of the reduction is caused by regional drawdown of the Floridan Aquifer from pumping as far away as Jacksonville.

Average flows in the Ichetucknee River System will continue to remain lower than historical flows unless local and regional groundwater pumping rates are reduced.

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Effluent Spraying in the Ichetucknee Springshed
Photograph by Wes Skiles

 

Increasing Pollution Means Dirty Water

Water quality in the Ichetucknee River System is damaged, as demonstrated by the decline of diversity of submerged aquatic plants and the increase in filamentous algae observed in the system.

Biologists at Ichetucknee Springs State Park began monitoring the submerged aquatic vegetation in the Ichetucknee River in 1989. Historically, the river supported numerous different kinds of underwater plants. During the past two decades, however, strap-leaf sagittaria and eelgrass have greatly increased in dominance while other species of submerged plants have declined, resulting in a noticeable loss of plant diversity.

In a recent article about the Ichetucknee in a local magazine, a young writer mentioned the “slimy leaves” of the river grass. Too young to have seen the river when it was pristine, she did not realize that the “slime” was really algae and not the grass itself.

The filamentous algal growth that now covers much of the underwater plants in the Ichetucknee River has increased greatly over the past two decades. The algae damages the underwater ecosystem by clouding the water and shading the plants, which reduces their vigor and reduces the food that is available at the very base of the Ichetucknee’s food web.

Algal growth can be attributed to nitrate pollution. Nitrates, which are byproducts of human and animal waste, are a contributing factor in the Ichetucknee’s decline. Groundwater nitrate concentrations in the most vulnerable areas of Florida have typically increased from a pre-development level of less than 0.05 milligrams per liter (mg/L or parts per million) to more than 1 mg/L because of human land use alterations.

Average nitrate concentrations in the Ichetucknee Head Spring have increased from about 0.05 mg/L before the 1960s to about 0.78 mg/L during the most recent decade, an increase of more than 1500%. Groundwater nitrate concentrations are elevated throughout the most vulnerable portions of the Ichetucknee Springshed. The primary culprits are inorganic fertilizers on agricultural lands, lawns and pine plantations; animal waste; and septic tanks.

 

Summary/The Way Forward

As conveyed in Ichetucknee Springs & River Restoration Action Plan prepared by the Howard T. Odum Florida Springs Institute, science tells us not only that the Ichetucknee River System is damaged, but also how that damage is occurring—through increasing withdrawals from the Floridan Aquifer and increasing pollution that is entering our waters.

Different scientists, however, will advance different arguments. The most prominent of those other arguments is to lay blame for our water damage on long-term drought.

Faced with uncertainty and/or conflicting opinions, it is easy for water managers to stymie calls for action by insisting on more scientific studies of our water situation. While more studies are always helpful from the scientific viewpoint, we also need to take into account the fact that our waters are already damaged and may well suffer more damage unless we act now.

We need to remember that even though science is a human endeavor, it was never designed to tell us what we should do in the face of conflicting scientific opinions. To make decisions about what we should do, we may turn to the disciplines of morals and ethics. One good guideline offered by these disciplines is the Precautionary Principle:  When faced with the possibility of causing grave harm to a natural resource, we are justified in taking action even in the face of conflicting or imperfect science.

In other words, we should not have to wait for perfect science to take action to protect our waters. Since damage to the Ichetucknee has already occurred and appears to be ongoing, we can feel justified in taking actions now to reduce groundwater pumping and to reduce the amount of pollution that is entering our waters.

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Watching
Photograph by Wes Skiles



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