HYDROLOGY AND WATER QUALITY IN A HEAVILY URBANIZED ESTUARY – FLUSHING BAY

Small embayments in highly transformed urban estuaries like the New York – New Jersey Harbor are not often studied, despite the current interest in submarine groundwater discharge. Flushing Bay, adjacent to LaGuardia Airport, has had a long history of poor water quality due to coliform and other contamination, even as water quality parameters have rebounded in the larger Harbor area. However, major investments have recently been made in reducing discharges from combined stormwater outflows (CSO) into Flushing Bay. In addition, the switch to drinking water supply from upstate reservoirs instead of groundwater pumping in Queens should cause a doubling of groundwater discharge into the Bay over the next 15 years. Therefore, water quality is poised to improve.

We present baseline data on water quality and salinity from ten locations around the Bay, sampled at different points in the tidal cycle. At one location, daily samples were analyzed for total coliforms, which is known to vary with precipitation at LaGuardia Airport. Spatial patterns of water quality were also hypothesized to be related to the tidal cycle, the role of a breakwater extending from the airport, and the distance of sampling locations from the dredged main channel. Preliminary data suggested that water quality degradation occurs between the lakes in Flushing Meadows Corona Park, where estuarine wetlands and the former Flushing Creek were filled in 50 years ago, and the open waters of the Bay.

Since natural surface water input is now minimal, Flushing Bay is an end-member of alluvial estuaries, for which analytical solutions of the St. Venant equations have been developed to describe one-dimensional tidal flow (Savenije 2005). These solutions depend on longitudinal estuary width and cross-section variation according to exponential functions, which is approximated by the geometry of Flushing Bay. Tidal and salinity data will be presented in comparison to these theoretical solutions.