PARTITIONING PHOSPHORUS LOADS - IMPLICATIONS FOR LAKE RESTORATION

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.