A Historical Perspective on Water Levels and Storage Capacity of Lake Okeechobee, Florida: Pre- and Early Drainage Periods

Legally mandated eutrophication restoration goals for Lake Okeechobee (FL) are unachievable, therefore assigning managers a "mission impossible." Since the 1970s, restoration efforts have focused on reducing pelagic total phosphorus (TP) to 40 mg/L. A total daily maximum load (TMDL) of 140 metric tons (t)/yr was adopted by the Florida Department of Environmental Protection in 1999 (effective date 2015) to restore the lake's balance of flora and fauna. Phosphorus (P) loads (1975-2018) averaged 516 t/yr with no significant change over time, yet average TP significantly increased from 51 mg/L (1974-1977) to 146 mg/L (2015-2019). Greater TP values in 2019 were due to Hurricane Irma and an early June storm event. Annual P-loads and pelagic TP were not significantly correlated. Instead, TP was strongly correlated with turbidity (R 2 ¼ 0.85), which is generated by wave-driven resuspension of P-rich unconsolidated sediments. Since 1973, >13,000 t of TP has been added to Okeechobee's sediments that have accumulated over the past century due to the lowering of water levels and the construction of the Herbert Hoover Dike. Prior to settlement, high water levels allowed turbid lake waters to flood large areas of adjacent wetlands, where suspended sediments were removed from the lake. With the minimization of this self-cleansing mechanism after construction of the Herbert Hoover Dike, P-rich fine sediments accumulated, and periodic hurricanes disrupted consolidated sediments. Unconsolidated sediments are easily resuspended into the water column, raising TP. Efforts to reduce Okeechobee's pelagic TP through reductions of P-loads alone will not work due to sediment accumulation and resuspension.

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Understanding the ups and downs: application of hydrologic restoration measures for a large subtropical lake

Julian

Welch

2022

Lake and Reservoir Management

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Hydrologic regimes in shallow lakes strongly in uence the system's function and ecology. Changes in water levels can have nonlinear, disproportionate effects in these low gradient systems. High water levels can submerge upper elevation littoral areas, degrade benthic habitats, and redistribute sediments and nutrients throughout the lake. When water levels are low, wetland littoral areas are dried out, prompting shifts in plant communities. Lake Okeechobee, a large shallow lake, is a diverse and complex ecosystem managed for multiple purposes. Currently, water levels within the lake are managed based on the Lake Okeechobee Regulation Schedule of 2008, which is being replaced due to the completion of key restoration projects. The new regulation schedule, Lake Okeechobee System Operating Manual (LOSOM), updates water management rules while attempting to balance the needs of downstream systems; salinity and water quality in the Caloosahatchee and Saint Lucie estuaries, and more water for the southern Everglades. This study evaluates LOSOM relative to ecologically signi cant performance measures for the lake. Overall, the proposed regulation schedule is expected to cause deeper average lake levels, increased occurrence of damaging high-stage events, and reduced frequency of low-stage events. While decreases in the severity and frequency of low stages will be bene cial, increases in high stages may impact the long-term ecology of the system. As lake management shifts to optimize restoration efforts around and downstream of Lake Okeechobee, restoration projects upstream of the lake become critical to building and improving resilience in this central South Florida ecosystem.

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A Historical Perspective on Water Levels and Storage Capacity of Lake Okeechobee, Florida: Pre- and Early Drainage Periods

Cited by 4 publications

References 12 publications

Removal of Physical Materials From Systems Loss of Space, Area, and Habitats

Removal of Physical Materials From Systems Loss of Space, Area, and Habitats

Restoration of Lake Okeechobee, Florida: mission impossible?

Understanding the ups and downs: application of hydrologic restoration measures for a large subtropical lake

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