Upstream water management and its role in estuary health, evaluation of freshwater management and subtropical estuary function

•Understanding the tradeoff of freshwater inputs from a highly managed system to an estuarine system is critical for ecosystem function.•More sustainable flow regimes into estuarine systems reduce ecosystem stress and builds resilience.•Water management rules combined with restoration infrastructure allow for better water management for ecosystem health and flood protection. In highly modified and managed systems the balance of freshwater inputs discharged to estuarine systems are important to maintain salinity balances and thus estuarine function. However, the availability of freshwater is highly dependent on upstream water management to provide flood protection whilst meeting freshwater demand for people and the environment. In South Florida, water is managed by a water control plan with Lake Okeechobee at the center. Currently, water levels within the lake are managed based on the Lake Okeechobee Regulation Schedule of 2008. 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 (northern) estuaries; and more water for the southern Everglades. This study evaluates LOSOM relative to ecologically significant performance measures for the northern estuaries. Overall, the proposed regulation schedule is expected to provide a more sustainable flow regime to the estuaries by reducing stressful and damaging discharge events. Moreover, new management rules combined with new infrastructure are expected to reduce low discharge events to the Caloosahatchee estuary and reduce stress on key indicator species such as Vallisneria americana during the wet season. This regulation schedule provides improved conditions for the estuaries at the expense of higher Lake Okeechobee stages. Future restoration and water management will maintain the benefits afforded to the estuaries while at the same time reducing the impacts to Lake Okeechobee resulting in a more sustainable and resilient system.