Why do springs ‘brown-out’ during and after floods? During high water events, spring flow can come to a stop causing a ‘brown-out,’ or a flow reversal into the aquifer. Rum Island after tropical storm Debbie does appear to have stagnated but did it go into a complete reversal? A spring reversal occurs when the hydrostatic ‘head’ of the river overwhelms the weakened aquifer.
I first witnessed a spring reversals at Hornsby Springs nearly twenty years ago. Now that spring hardly flows at all. Matt Cohen has been studying this phenomenon in the Suwannee River basin. His analysis of nearly 100 years of data has determined that there is a “massive decline in flow gain since the 1990’s equivalent to the loss of six Magnitude One springs adding that ” Springs never reversed before and now they reverse all the time. Fanning Springs is dark most of the time.” Cohen’s study includes the confined Suwannee River basin and the mostly unconfined Ichetucknee Spring Run and the Santa Fe River. Is Rum destined to be predominantly tannic like Worthington, and Santa Fe Spring on the Santa Fe ? What role does overconsumption of our aquifer play in these dynamics?
Another interesting result of spring reversals is their reduction of dissolved oxygen and the subsequent increase in algae growth. Cohen’s research indicates that algae growth is greatest in low oxygenated waters, whereas high oxygen levels sustain subaquatic vegetation (SAV) that nurtures fish and other wildlife. Spring reversals depress dissolved oxygen, encouraging algal growth and discouraging healthy SAV. Does the increase in consumptive use of our aquifer play a role in reduction in flow from our aquifer? Does our increased water use play a role in the frequency of spring reversals that reduces dissolved oxygen (DO), leading to an increases in algae growth?
Tom Morris writes ” Low aquifer levels allow river back-flow to penetrate farther into springsheds and extend the residence time of the river water in the aquifer. If the water resides in the aquifer long enough, the natural processes mentioned above may depress DO concentrations to lethal levels. Morris encountered this situation in White Sulfur Springs (Hamilton County) after oxygenated back-flow water stagnated, declined in DO, and killed every white catfish in the cave. Similar incidents have been documented in Peacock Springs, as discussed above.”
Cohen adds, “We’ve seen reversals this last 12 months at nearly all the Suwannee and Santa Fe springs. Even at Gilchrist Blue (which is rare) ” To learn more about spring reversals, check out Cohens’ many publications online or watch his video presentation A century of flow and flow reversals in the springs of the Suwannee River by Dr. Matt Cohen, YouTube · UF Howard T. Odum Center for Wetlands · Oct 5, 2023
Does the increase in population in our area, and increased irrigation, water bottling, mining (titanium, phosphate), have an affect on our aquifer and springs? What changes are you willing to make and will it be enough to reverse this trend? Are we seeing the beginning of the end of our beloved springs and wildlife abundant rivers?
OSFR President Joanne Tremblay
joanne.tremblay@oursantaferiver.org
“Giving Our River A Voice”
