Abstract

The Lake Worth Lagoon is an urban subtropical estuary impaired by discharge conveyed through the C-51 canal. To date, the origin of impairment has not been rigorously demonstrated. This study successfully applied a balance-of-flow framework to identify the predominant water source(s) conveyed to the S5A Complex, located at the headwaters of the C-51 canal. The results reveal distinct seasonal differences. During the dry season, water delivered to the S5A Complex was predominantly derived from Lake Okeechobee. During the wet season, agricultural runoff was the predominant source. Over the duration of the study, S5A Complex water management operations released 72% of the annual flow into the C-51 canal during the dry season. During the wet season, the predominant source of water flowing through the C-51 canal was locally derived from urban stormwater runoff. These findings contradict previous studies that have reported that Lake Worth Lagoon pollutant loads are derived from wet-season agricultural runoff. The analysis also revealed that recent construction upgrades designed to improve the quality of water released to the northern Everglades have (1) reduced the volume of lake water delivered to the S5A Complex during the dry season and (2) created a novel water source that, at times, contributes substantially to the S5A Complex. The results of this study deviate substantially from the currently accepted paradigm regarding the origin of Lake Worth Lagoon impairment, thus affirming the value of the periodic reassessment of adaptive management plans to ensure resource management and restoration strategies are based upon the best available information.

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