Long-Distance Cavernous Flow in the Upper Florida Aquifer, Woodville Mantled-Karst Plain, Leon and Wakulla Counties, Florida

A Rhodamine WT dye study was conducted to establish whether a subterranean flow could be positively demonstrated between Lake Jackson, a shallow perched lake, and Wakulla Spring, a renowned first magnitude spring. The lake is 30.6 km north of the Spring and 8 km north of Tallahassee, Florida. Dye was injected into a lake-bottom sinkhole on September 19, 2017, for 6.5 min. The main distinctive dye concentration peaks were recorded by sondes located at both Wakulla Spring and nearby Sally Ward Spring after 35 days. Charcoal packs deployed at these two springs and three others nearby also encountered dye within time intervals consistent with the recorded breakthrough events measured by the sondes, all of which were of short duration ranging from 1 min to 100 min. These results indicate that some of the injected dye made its way to several Wakulla County springs via an aquifer conduit-like system dominated by advection within which water flowed at an average speed of 0.8 km d−1. Dye detection at five well-separated springs further indicates that the conduit system is both braided and branching. Although these results show a connection between Lake Jackson and several Wakulla County springs and point to a leaky-conduit flow able to transport nutrients and pollutants rapidly over long distances, another important conclusion of the study is that, overall, very little of the dye injected into the lake-bottom sinkhole made it to Wakulla Spring. This indicates that most of the dye dispersed into the limestone matrix. This study has been exploratory in design and only allows conjectural statements on the actual dye-mass balance