New York
Toxic algae in Ulster County lakes
13 lakes and waterways in Ulster County have harmful algal bloom reports in New York's official data. The most recent entry is for Rondout Creek: Rondout Creek was on New York's harmful algal bloom list from 3 September 2025 to 24 October 2025, with confirmed bloom status (24 reports). Rondout Creek, Wallkill River and Chodikee Lake and 1 more have had blooms in three or more years.
Lakes with bloom history
Newest report first. Each lake has its own page with the full history and what the results mean.
Other waterbodies with a report
These have one or two reports in a single year, which isn't enough history for a page of their own yet.
- Davis Lake 2020
- Esopus Creek 2017
- Fourth Lake 2025
- Lower Esopus Creek 2025
- Quassaic Creek 2022
- Seewackamano Lake 2020
- Tillson Lake 2015
- Ulster Heights Lake 2025
Source: New York State Department of Environmental Conservation (DEC), official data, checked 24 October 2026. For today's conditions see the NYHABS map. No report doesn't mean a lake is safe: most water is only tested occasionally.