Simulating the Response of Estuarine Salinity to Natural and Anthropogenic Controls

The response of salinity in Apalachicola Bay, Florida to changes in water management alternatives and storm and sea level rise is studied using an integrated high-resolution hydrodynamic modeling system based on Curvilinear-grid Hydrodynamics in 3D (CH3D), an oyster population model, and probability analysis. The model uses input from river inflow, ocean and atmospheric forcing and is verified with long-term water level and salinity data, including data from the 2004 hurricane season when four hurricanes impacted the system. Strong freshwater flow from the Apalachicola River and good connectivity of the bay to the ocean allow the estuary to restore normal salinity conditions within a few days after the passage of a hurricane. Various scenarios are analyzed; some based on observed data and others using altered freshwater inflow. For observed flow, simulated salinity agrees well with the observed values. In scenarios that reflect increased water demand (~1%) upstream of the Apalachicola River, the model results show slightly (less than 5%) increased salinity inside the Bay. A worst-case sea-level rise (~1 m by 2100) could increase the bay salinity by up to 20%. A hypothesis that a Sumatra gauge may not fully represent the flow into Apalachicola Bay was tested and appears to be substantiated.