The New York State Department of Environmental Conservation (DEC), in partnership with the New York State Water Resources Institute, is conducting a hydrographic dye study in the Little River/Tonawanda Island section of the Upper Niagara River in the city of North Tonawanda, Niagara County. The study will track the flow and dispersion of water from Aug. 26, 2025 to Aug. 27, 2025 and improve DEC’s understanding of the destination of the treated water.  

The data generated from the study will be used to assess feasibility of future potential treatment plans for the invasive Hydrilla verticillata plant, which is currently present in the Niagara River and undergoing treatment by the U.S. Army Corps of Engineers. 

The Rhodamine WT dye used for this study is a water-tracing dye approved for use by the U.S. Environmental Protection Agency (EPA) and will not cause environmental harm. Low concentrations of the dye will be introduced from three injection locations for eight hours around Tonawanda Island on Aug. 26 and 27, 2025. This is the only dye injection period scheduled during the study. The public is advised that due to the dye injection, portions of Niagara River may appear discolored and turn red or pink for a brief time. The discoloration is safe and may be visible from the shores.