Brevard County’s Indian River Lagoon

J. Martin Davis, P.E.

….. Is it the ghost of Christmas Future for Johns Lake?

     In November 2016 voters in Brevard County, by a margin of over 63 percent, approved a half-cent sales tax to provide $302 million over a 10 year period to clean up the increasingly polluted waters of the Indian River Lagoon. This water body has been increasingly threatened over the past 5 years by fish kills, algae blooms and increasing levels of nitrogen and phosphorous. About two-thirds of the money will go toward removing muck from the bottom of the lagoon, estimated to be just under 5 million cubic yards. Another $62 million will be spent for septic system removal and sewer plant upgrades to supplement the loss of the septic systems.

     At the risk of being overly alarmist, could there be parallels between the Indian River lagoon and Johns Lake? Population growth and the unending appeal of living on a body of water insures that development will continue on every available developable parcel on Johns Lake, just as it is occurring on the Indian River Lagoon. And, as we’ve explored in past Cattales issues (June 2016), several of the older communities on Johns Lake are on septic tanks, albeit the more recent development have been on sewer systems. We’ve also looked at the water quality parameters published by Florida Lakewatch since water sampling for Johns Lake began in 1989. This data indicated that the water quality parameters, including the all important nitrogen and phosphorous levels, have remained relatively stable.

A clue to this serendipity may lie on the graph of Johns Lake historical water levels, included below, which was also included in the last issue of Cattales.

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Johns Lake Levels 1959-2016

    You will note that lake levels appear to reach very low levels at approximately 20 to 25 year intervals, as evidenced by the low lake levels that occurred in 1980 and 2001 where the low water levels were around elevation 86 or less. It’s difficult to visualize the impact of this lake level until one sees, as is shown by the included aerial photo of Johns Lake, circa 2002, just how much of the lake bottom is exposed by these drought events.

     But this fluctuation of water level in Johns Lake is actually a very beneficial and helpful attribute of our lake. See, Johns Lake does not have springs or streams that provide a constant source of water into the lake. Rather our lake relies on rainfall, runoff and groundwater levels to replenish and maintain lake water levels. As such, our lake water levels are quite variable, as variable as the Florida weather. 

     But this is actually a major benefit in terms of maintaining water quality. During these periodic dry spells and the ensuing drop in water levels, large swaths of the lake bottom are exposed to the drying effects of sun and wind on any accumulated muck that may have been deposited on the lake bottom, drying out and blowing away the muck that otherwise might remain and accumulate indefinitely. If the Indian River Lagoon had these fluctuating water levels, it is unlikely $200 million would now be spent on muck removal.
So, we’re golden, right. With this built-in environmental lake bottom vacuum cleaner we’ve got, we’re good
to go …right? I think not so fast. 50 years ago the environmental pollutants that now affect the Indian River
Lagoon were by and large unidentified, or at least ignored. Let’s keep our collective heads up lest we suffer
the same fate.