The Southwest Florida Water Management District (SWFWMD) is recommending allowing up to an 8 percent flow reduction in the Chassahowitzka river system and a 5 percent reduction for the Homosassa river system — lower for Chassahowitzka and higher for Homosassa than was recommended during a contentious round of evaluations in 2013, after which the governing board set the rates for both at 3 percent.
Initial staff recommendations that year called for a flow-reduction rate of 9 percent for Chassahowitzka and 3 percent for Homosassa. After that 2013 rate was set for both rivers, the board required a re-evaluation of the minimum flow after six years, rather than the usual 10. The most recent recommendations are part of that re-evaluation.
Minimum water levels and/or flows set limits on water withdrawals from resources to avoid "significant harm" being done to them. MFLs define how often — and for how long — high, average and low water levels and/or flows should occur to prevent significant harm to the waterway, including in its role as a habitat.
“This is saying that ... you don’t hit the significant-harm threshold until you’ve hit an 8 percent reduction caused by groundwater withdrawal,” Jennette Seachrist, director of resource management for SWFWMD, said in a presentation to the Chronicle editorial board Wednesday, Jan. 9. “Based on the data and science and tools we have today, this is the best we can be. This is solid.”
Data gathered and changes made to criteria since the minimum flow was set at 3 percent six years ago helped SWFWMD staff arrive at the new recommended rates, Seachrist said.
“We identify what is the most critical, sensitive criteria to that system, and look at those models to identify and predict the impacts to those (criteria),” she explained. “Low salinity is one very critical, sensitive criteria. It’s needed for all kinds of ecosystems, to support the fish nurseries — it’s very critical, low-salinity habitat. So that’s a criteria we’d be looking at and developing models to predict — what the impacts to that low-salinity habitat would be. Another would be manatee habitat.”
The six years since the last recommendations allowed SWFWMD staff to gather and consider more data than was available in 2012 and 2013, Seachrist said, and the new data includes water-quality sampling.
“We collect the best information that’s available. ... The Florida Fish and Wildlife Conservation Commission and Department of Environmental Protection also collect data, and we use it all for the analyses,” she explained. “We have all this new data ... especially in the spring systems and especially with sea-level rise, we’ve got a lot of things that potentially can change in a very dynamic system, and we want to do re-evaluations because the science and data improve.”
Another change: The new recommendations are based on the habitat needs of the common snook, which Seachrist said is the most sensitive species available for consideration.
“This is different for us — we worked with Fish and Wildlife and identified a more sensitive species for that low-temperature habitat,” she said. “We’re still protecting the manatee habitat. ... If you remember after that freeze in 2010, snook fishing was cut off for a few years until the fisheries rebounded. So it was important for us to see if there was a way to look for another criteria that would be more protective.”
Draft reports will be available online at watermatters.org/MFL later this month, Seachrist said, and the peer-review process starts in late January. A public meeting has been tentatively scheduled for June, and comments can be submitted to MFLComments@WaterMatters.org.
For more information and available documents, visit swfwmd.state.fl.us/projects/mfls.