The Importance of the Lower Floridan Aquifer in FL’s Water Future

With Florida becoming the third-most populated state, it has been said that groundwater, or more specifically the Floridan aquifer system (FAS), may be approaching a critical tipping point as a relatively cheap and accessible water supply. While that may be true for different zones of the FAS in certain areas of the state, if water managers and researchers are successful, the lower Floridan aquifer (LFA) may potentially be the solution, or at least a temporary solution, to many of the water woes facing Floridian utilities.

To many in the state, the aquifer systems in peninsular Florida are “layer cake”, generally made up aquifers separated by confining units. However, the karst aquifer systems in Florida are actually very complex. The Cenozoic sediments of Florida, which were first deposited in a shallow sea 65 million years ago, form a series of aquifer systems with varying degrees of connectivity, which currently provide greater than 90 percent of the drinking water for the state. The prominent aquifer systems in the State of Florida include: the Floridan, both upper and lower; intermediate; and surficial. While each of these aquifers may be separated from one another by one or more confining layer(s) of varying thickness and continuity, there are areas of the state where there is no confinement between aquifers.

The majority of the groundwater withdrawals for water supply in Florida target the upper Floridan aquifer (UFA) due to the good water quality and yield. Withdrawals from the UFA in areas where there is little to no confinement or breaches in the confinement, such as sinkholes, have had adverse impacts to the surficial aquifer (SA) which supports lakes, wetlands, and streams. These UFA withdrawals have also impacted Florida’s springs. These withdrawals have severally limited future development of the UFA as a future water supply, as Minimum Flows and Levels (MFLs) are continually being established by Florida’s Water Management Districts (WMDs) to protect and maintain these systems for future generations.

In many parts of Florida, there is much to learn about the LFA. Where is it present; the water quality and quantity available; where is it recharged; and very importantly, is the confinement thick and consistent enough to adequately separate it from the UFA and the environmental impacts that could be associated with its development? With the UFA historically being relied upon as a water resource due to the water quality, yield, and accessibility and with a limited water quality and yield dataset for the LFA, very few Floridian utilities found it economically necessary to evaluate the LFA as a water source. Based on the limited dataset across the state as compared to the massive UFA dataset, the LFA has significant data lapses with respect to water quality. While in some areas of the state, the LFA water quality is comparable to the UFA, in other areas of the state, the LFA water quality would result significant treatment and associated treatment costs to meet potable water quality standards. This water quality and yield can result in difficult economic decisions for a utility.

Another key question is whether the WMDs will classify the LFA as an Alternative Water Source (AWS). An AWS designation is a key consideration to important administrative and regulatory decisions that are made by the Districts. The inconsistencies between WMDs to classify the LFA as an AWS is an important hurdle as to whether the development of this water source would qualify for cooperative funding from the Districts. For example, the St. Johns River Water Management District (SJRWMD) currently characterizes the LFA as an AWS, while the Southwest Florida Water Management District (SWFWMD) does not if the water quality is considered potable!

The answers to the questions regarding the LFA are extremely important to the efforts of at least three regional organizations grappling with their estimated future growth and the water it will take to sustain it. The Withlacoochee Regional Water Supply Authority (WRWSA); the CFWI; and the South Lake Regional Water Initiative (SLRWI) are all analyzing a 20-year planning horizons and the traditional water and AWS that will be necessary to develop to meet a growing population demand. In each of these efforts, professionals are dealing with existing impacts to MFLs from groundwater withdrawal and how to mitigate them; the lack of sustainable traditional water supplies, both surface and groundwater; the need for water conservation; the scarcity of AWS like reclaimed water; and skyrocketing population growth. Based on the current regional LFA dataset for each of these organizations, the water quality and yield of the LFA is promising. The LFA can and will play a significant role meeting these challenges and ultimately will be an important piece of the “water pie.”

There are no definitive answers for the use of the LFA as a water supply. While some areas of the state, the LFA is promising; in others, it may be a necessary alternative with significant economic implications and ramifications that a utility would be forced to bear. The economics of the LFA as a source can only be determined by thorough hydrogeologic research of the region, including discussions with hydrogeologic experts and the WMDs, and the investment in LFA exploration to get site-specific hydrogeologic data to determine and vet the LFA as a viable water supply source.