Partitioning Phosphorus Loads: Implications for Lake Restoration

Abstract

An extensive tributary monitoring program was undertaken to evaluate phosphorus loads to Onondaga Lake—a hypereutrophic water body near Syracuse, New York. The resulting phosphorus budget indicates that diversion of treated wastewater discharges achieves the greatest reduction in load. However, application of a simple water‐quality (trophic state) model suggests additional remediation of contributions from other (tributary) sources is necessary to reach lake restoration objectives. Analysis of loadings from Onondaga Creek—the second largest phosphorus contributor to Onondaga Lake—indicates that, on a unit area basis, urban sources account for a disproportionately high fraction of the tributary load. Phosphorus contributions from rural sources exhibit a significant increase during extreme, short‐term hydrologic events, possibly as a partial result of effusions of soft sediments (mud boils) triggered during periods of high flow. Findings reveal the importance of developing a comprehensive, basinwide phosphorus control strategy for Onondaga Lake—a strategy that considers remediation of rural and especially urban sources within critical reaches of Onondaga Creek. Leaky sewers and combined sewer overflows, together with possible mud‐boil effects and runoff from urban and rural areas, should all be addressed within the context of the aforementioned strategy.