The file "Chloride_specific_conductance_regression_model_forms_for_estimating_high-frequency_chloride_concentrations.csv" contains the regression equation forms for two types of regressions: 1) single linear (SLR) and 2) piecewise (or segmented; SEG) regression between specific conductance (SC) and chloride (Cl) concentrations for 56 USGS water-quality monitoring stations across the eastern United States, plus four regional regressions developed by pooling data for sites within a region (see Moore and others (in review) for more information). Some sites, and all regions, have both SLR and SEG models reported in this table. The analysis included in the Moore and others (in review) study used results from the SLR models if those are the only model reported, or the SEG models are both reported. This data set includes the slope, intercept, model correlation coefficient (R2) and the number of observations used to develop the regression equation for the SLR models. For the SEG models, information on the slopes and intercepts for the two linear segments are included in addition to the coefficient of determination (R2) and number of observations. Breakpoint estimates (the point separating the two line segments) and uncertainties are only reported for the SEG models. Moore, J., R. Fanelli, and A. Sekellick. In review. High-frequency data reveal deicing salts drive elevated conductivity and chloride along with pervasive and frequent exceedances of the EPA aquatic life criteria for chloride in urban streams. Submitted to Environmental Science and Technology.