ATM was contracted by the SRWMD to develop Minimum Flows and Levels (MFL) for the Steinhatchee River. In support of the MFL, ATM developed, calibrated, and implemented a hydrodynamic model of the tidal Steinhatchee River. In support of the hydrodynamic modeling, ATM performed a comprehensive data collection installing continuous water level, salinity and temperature gages within the estuarine portion of the river. The hydrodynamic model was calibrated against the continuous data. The hydrodynamic model was utilized to evaluate salinity and water level regime changes resulting from changes in inflow conditions, with several flow reduction scenarios and one sea-level change scenario being evaluated. Changes in salinity influencing habitat availability due to reductions in freshwater inflow were used to inform the development of an MFL for the two rivers.
Additionally, ATM modified an existing HEC-RAS Model in order to assess riverine Water Resource Values (WRVs) in the upper reaches of the system under varying flow withdrawal scenarios. Specific WRVs evaluated included fish passage, habitat suitability, and flood plain inundation. The MFL was defined based on maintaining adequate freshwater and marine habitat.