An examination of water quality in the South Bay Salt Pond Restoration Project

The South Bay Salt Pond Restoration Project (SBSPRP) was established in 2003 from 15,100 acres of former Cargill salt harvesting ponds in the San Francisco Bay Area. Since then, the SBSPRP has utilized an adaptive management framework to restore the ponds with the goal of habitat restoration, public access, and flood protection as its guiding principles. The SBSPRP is the largest wetland restoration project on the West Coast and the complexity of the project is compounded by nearby land use, including wastewater treatment plants (WWTPs) and urban development. The majority of previous water quality studies in the area have primarily focused on legacy pollutants, such as methylated mercury. In the SBSPRP and the South SF Bay as a whole, eutrophication and hypoxia are issues of ongoing concern. During the summer of 2016, a selection of Alviso ponds with diverse management histories were sampled for water quality parameters including dissolved oxygen (DO), nitrate (NO₃⁻), and ammonium (NH₄⁺) during spring and neap tides. Nutrient concentrations were positively correlated with DO values; distance to WWTPs was negatively correlated with DO. When examining change in DO from pond inlet to outlet, volume was negatively correlated. Pond management regime and tidal action also influenced the change in DO, suggesting that residence time may be a control on DO levels in the SBSPRP. These results suggest that greater considerations for DO and other water quality parameters may be of use in future adaptive management strategies in the SBSPRP, both in making new management decisions and anticipating effects of selected actions.