Assessment Study

Silver Birch Pond

Princeton Hydro was selected to conduct a detailed study of Silver Birch Pond for the purpose of gathering and reviewing key pond and watershed data that could be used as the foundation for a preliminary water quality improvement plan. Of immediate concern to the residents abutting the pond was the interaction between the pond’s aquatic macrophytes and fishery resources, persistent algae blooms, influxes of sediment, and eroded sections of shoreline. Two of the key tasks directly related to the resident’s and town’s concerns were the implementation of a bathymetric survey, and sampling of the pond’s macrophyte and benthic algae communities.

The bathymetric survey generated up-to-date metrics of Silver Birch Pond’s average depth, maximum depth, and lake volume. Princeton Hydro analyzed the physical and chemical qualities of the pond’s sediments and mapped the distribution, depth, and volumes of unconsolidated sediment present in the pond. These data were subsequently used to assess the utility and feasibility of dredging.

The community had concerns about the lack of plants in the pond and the impact this might have on maintaining a healthy fishery. Although complaints were voiced concerning “weeds,” this had more to do with benthic algae and phytoplankton blooms than with macrophytes. The line-intercept method was used to monitor and map plant growth and distribution. In addition to these transects, a complete perimeter inspection of the pond was conducted during each of the four sampling events to ensure no plants were overlooked. During these macrophyte surveys, the density and distribution of benthic algae and phytoplankton densities were assessed, and in-situ water quality was measured.

The bathymetric survey and sediment analysis showed that dredging of the pond was a low-priority management option. It was also documented that Silver Birch Pond was severely lacking with respect to aquatic plants. This is a function of the kettle-hole nature of the pond and the minimal width of the pond’s littoral zone; both limit the physical habitat where plants can actually grow. Additionally, phytoplankton densities were great enough to impact clarity and restrict the depth to which plants can grow. It was also concluded that the lack of plant growth was negatively affecting the fishery. The final report identified management measures having the greatest potential to decrease pollutant loading to the pond and improve its overall ecology. The report was presented to the residents in a public forum setting.