Causal effects of urbanization and winter weather on salinity in the Delaware River Basin

Salinity is increasing in freshwater reaches of rivers around the globe, including in the Delaware River Basin, located in the mid-Atlantic region of the United States. This study estimates the causal effect of land use changes on in-stream salinity concentrations in the Delaware River Basin. A 1% increase in urbanized areas increases salinity by 3 mg/L, or about 16%. Freezing precipitation, which leads to salt from deicing applications, also increases salinity, particularly in watersheds with developed land uses. Simulating salinity levels based on land use and climate projections indicates that, even in a warming climate with reduced deicing, more development increases in-stream salinity.