Discrete chloride and specific conductance (SC) measurements, chloride-SC regression equations, and daily and hourly mean SC values and chloride predictions for 88 USGS water quality monitoring stations in the Delaware River Basin, 2019-2022

Freshwater salinization, or the increase of dissolved ions like chloride, threaten freshwater streams and rivers across the globe. Continuous (e.g., daily or hourly mean) predictions of chloride concentration were used in an analysis to quantify the extent to which chloride concentrations exceeded ecological thresholds at U.S. Geological Survey (USGS) water quality monitoring sites across the Delaware River Basin, USA. Predicted hourly mean or daily mean chloride concentrations were generated using regression equations developed from discrete measures of specific conductance (SC) and chloride. These regression equations were applied to continuous SC values at each site to predict chloride concentrations. When discrete measures of chloride were not available at a USGS sites, a cluster-based regression equation was applied to continuous SC data to generate predicted chloride concentrations. Cluster-based regression equations were developed by pooling discrete SC and chloride measurements from additional sites in the Delaware River Basin that have similar watershed characteristics identified through a cluster analysis. Predicted chloride concentrations were generated for 88 USGS continuous SC monitoring sites, including 82 non-tidal sites and 6 additional sites that were considered tidal.

This data release contains the following datasets:

1. [Site_information.csv]: This file contains general site information, including siteID, a short identifier to identify sites used throughout the data release.

2. [Discrete_SC_Cl_observations.csv]: This file contains discrete measures of chloride and SC used to create SC-chloride regression equations.

3. [Watershed_characteristics.csv]: This file contains watershed characteristics, such as land use/land cover and geological setting, used to group sites with water quality information together for the development of cluster-based SC-chloride regression equations.

4. [Regression_equations.csv]: This file contains SC-chloride regression equations and summary information about the discrete SC and chloride measurements used to create the regression equation.

5. [Daily_SC_chloride_data.zip]: This is a zipped folder containing 88 .csv files for each continuous USGS water quality monitoring station. The individual files each contain daily mean SC values and chloride predictions for October 1, 2019 through September 30, 2022.

6. [Hourly_SC_chloride_data.zip]: This is a zipped folder containing 88 .csv files for each continuous USGS water quality monitoring station. The individual files each contain hourly mean SC values and chloride predictions for October 1, 2019 through September 30, 2022.