An Ecoregion Approach Characterizing Chloride Concentrations in New York State Flowing and Ponded Waters

Abstract

Abstract In the United States, chloride (Cl) concentrations in surface waters are increasing nationally. Analysis of water quality trends in New York State (NYS) surface waters demonstrated Cl concentrations are increasing in some areas. Within the literature, considerable focus has been given to understanding the drivers and cumulative effects of Cl concentrations in the water column, but more work is needed to understand spatial patterns and the variability of Cl in the aquatic environment. To evaluate the gradient of Cl concentrations in surface waters across NYS, 13,690 discrete samples, collected between 2001 and 2019, from 1,661 unique locations were aggregated and compared among Level III United States Environmental Protection Agency (USEPA) Ecoregions and classified into novel, regionally distinct NYS Cl Ecoregions (ClE). Median Cl concentrations in the ClE correlated with land cover patterns. Maximum Cl concentration for each sampled location were compared against NYS’s Health (Water Source) water quality standard (WQS) of 250 mg/L and USEPA’s aquatic (chronic) 230 mg/L criteria. The frequency of flowing and ponded water sampling locations in NYS with a concentration above the NYS WQS (0–3%) or USEPA criteria (1–4%) are low but vary by ClE (0–11%). The characterization of statewide condition represented here provides needed context to water quality managers about the relative condition of their waters and potential for Cl impacts. The ClE approach provides a potential framework for development and implementation of future Cl management strategies based on regional condition enabling a balanced approach between restoration of water quality and protection priorities.