RECOVER MAP 3.3.3.4 SAV Monitoring for Caloosahatchee Estuary 2004-2007 CP040627

The Caloosahatchee River and Estuary are located on the southwest coast of Florida (Figure 1). The Caloosahatchee River runs from Lake Okeechobee to the Franklin Lock and Dam (S-79) where it empties into the estuary which is some 40 kilometers long and terminates at Shell Point. The Calooshatchee River is the major source of freshwater to the estuary. Enough water enters the estuary at S-79 to fill its volume over 8 times per year.
The hydrology of the Caloosahatchee system has been altered over time. The river has been permanently connected to Lake Okeechobee and about 20% of the water entering the estuary now comes from the Lake mainly as regulatory releases to maintain the Lake at a prescribed water level. The river has also been straightened, deepened and three water control structures have been added. The last, Structure S-79, was completed in 1966 to act, in part, as a salinity barrier. The result is that freshwater delivery to the estuary has been altered and shows characteristics consistent with a watershed that has lost storage capacity. Storm water is not retained but runs off quickly and at higher peak flows. Because there is no retention base flows are low or nil during the dry season.
The combination of over-draining and the addition of S-79 as a salinity barrier results in a truncated and highly variable salinity gradient in the estuary. During periods of low freshwater discharge typically during the dry season, salt water regularly intrudes all the way to the structure, often exceeding 10 psu. By contrast, high freshwater discharge can cause salinity to drop below 5 psu at the mouth. The transition between the two states can be rapid, sometimes requiring less than a week. The fluctuations observed at the head and mouth of the estuary exceed the salinity tolerances of oligohaline and marine species.
The South Florida Water Management District and the U.S. Army Corps of Engineers are trying to fix these problems through regulation and the construction of additional infrastructure. The South Florida Water Management District has recently established a minimum flow and level for the Caloosahatchee River and Estuary to partially address the lack of freshwater inflow during a typical dry season. As part of the Comprehensive Everglades Restoration Plan (CERP), the C-43 Basin project will construct a reservoir and a number of aquifer storage and retrieval wells (ASR). These storage facilities will allow water to be retained during high flow periods, with subsequent release to the estuary during drier times. The infrastructure will thus reduce high discharges during the wet season and provide a base flow during the dry season. The Southwest Florida Feasibility Study will examine the water requirements of Southwest Florida in more detail and suggest additional possibilities for water storage and management. All these programs, CERP (through RECOVER), C-43 Basin Project, the Southwest Florida Feasibility Study, and the Caloosahatchee MFL require monitoring of biological resources in the Caloosahatchee Estuary.
The implementation of this project is in response to the Monitoring Assessment Plan (MAP) created to determine how well the Comprehensive Everglades Restoration Plan (CERP) is meeting its goals and objectives. The premise of CERP is that restoring hydrology in Caloosahatchee estuary will improve the spatial and structural characteristics of submerged plant communities. The objective of this monitoring is to determine if the restoration of beneficial patterns of freshwater inflow, salinity and water quality to the Caloosahatchee Estuary will achieve the expected distribution, community structure and viability of submerged aquatic vegetation (SAV) beds. This monitoring will provide the scientific basis for quantifying the success of these projects.