Lake & Pond Management in New York City’s Central Park

In 2019 Princeton Hydro was contracted by the Central Park Conservancy (CPC) to develop a long-term and holistic management plan for the lakes and ponds in Central Park, New York City. These waterbodies provide important and integral aesthetic and recreational services for both residents and visitors of Central Park. While there are a number of water quality issues that impact these waterbodies, including high rates of sedimentation and localized nuisance densities of aquatic plants some of which are invasives species, the primary concern is the development of large and intense Harmful Algal Blooms (HABs).

In these freshwater, urban lakes and ponds, the HABs are entirely composed of cyanobacteria, a group of bacteria that “behave” like other algae. However, in addition to their nuisance surface scums and aesthetically displeasing blooms, they also produce cyanotoxins, which can negatively impact the health of humans, pets and wildlife. In fact, there have been documented cases of dog deaths directly attributed to cyanotoxins. Given these undesirable conditions and the potential for such impacts, the CPC hired Princeton Hydro to develop management plans for the lakes and ponds.

In 2020, Phase I of the project was initiated which included the review, analysis, and synthesis of various reports, site plans, engineering studies, and water quality data conducted over the course of decades at the Park. In addition, Princeton Hydro modelled the pollutant loading, hydrology, and trophic state of the waterbodies using these data to provide a base level of understanding of the systems and their management.

Over the 2020 and 2021 growing seasons, Princeton Hydro completed Phase II, which consisted of collecting a wide variety of physical, chemical, and biological data on the lakes and ponds. Phase II included the analysis of the collected data and the development of a framework of source control, watershed, and in-lake recommendations to address the HABs. The Phase II report was submitted and Princeton Hydro met with the CPC to discuss specific management measures for each waterbody.

Phase III was initiated in the second half of 2022 and will be completed in early 2023, which will include a management plan providing details on the management measures to be implemented on a short-, medium and long-term basis for each of the waterbodies. Phase III will also include details such as estimated capital and long-term maintenance costs, permitting requirements, and the establishment of criteria to be used to quantify success. Some of these management measures include, but are not limited to, the use of various types of nutrient inactivators and absorption products like Biochar, various types of aeration and circulation, the installation of Floating Wetland Islands, the use of source control and/or multi-waterbody circulation, and stormwater treatment.