SALINIZATION OF THE MOHAWK RIVER AND THE GREAT FLATS AQUIFER IN UPSTATE NEW YORK

New York State (NYS) leads the nation in use of road salt for deicing roads. Since the early 1950s, chloride levels in the Mohawk River in upstate NY have increased by >300%, and some of the most productive aquifers have been contaminated. We determined conductivity and concentrations of common dissolved ions in urban streams in Schenectady County, NY, and evaluated how solute loads may affect the adjacent Mohawk River. We also evaluated Na+ and Cl- in annual municipal drinking water reports from communities that use the Great Flats Aquifer (GFA), which has hydraulic connection to the Mohawk River. The GFA and Mohawk River are the raw water source for most municipalities in the lower Mohawk watershed. Streams in urban settings in Schenectady County have remarkably high sodium and chloride levels (peaks of 5-15 ppt) in the mid-winter when road salt is dissolved and runs off into surface water. Sodium and chloride values from annual water quality reports (and historic USGS data) for municipalities that draw water from the GFA and for those that draw directly from the Mohawk River reveal distinct salinization in the last few decades. Municipalities that draw from the GFA report an average of 45 mg/l for sodium and 88 mg/l for chloride – which is about twice that of the river. Of particular note is the Village of Scotia, which draws raw municipal water from a distal part of the GFA; this water shows the most dramatic effects of salinization. Chloride concentrations in the pre-road-salt days of 1943 were ~3 mg/l, but chloride had increased to ~ 63 mg/l between 2010 and 2012, and in the last four years has averaged 112 mg/l. In 2020 and 2021 the Village of Scotia surpassed the action level for lead (Pb). State-mandated lead-testing in Scotia-Glenville schools revealed a failure rate of 27%, with the most significant failures in the high school (45% of samples ≥ action level). The source of the lead in Scotia water is suspected to be corrosion of household plumbing. Recently Scotia initiated a corrosion control study, being one of the few communities in the Capital District of NY that does not use corrosion control. Adopting corrosion-control procedures will likely ameliorate corrosion and lead release. However, open salt storage on the GFA and oversalting in the winter still need to be addressed.