These are data stored on the EPA GeoPlatform based on ArcGis (ESRI). They are in the form ArcGis tables or Excel files.

This "Predicted Background Conductivity" view consists of a shapefile derived from National Hydrography Dataset Plus Version 2.0 which displays modeled natural background conductivity for the continental United States. The Natural Background Specific Conductivity (NBSC) contains predicted natural background conductivity using geology, soil, climate and other input parameters.

The "National Measured Conductivity Data - WQP" view consists of a shapefile derived from data stored in the U.S. EPA Water Quality Portal. The "National Measured Conductivity Data - WQP" is based on measured data obtained from the U.S. EPA Water Quality Portal (WQP) data inventory - the nation's largest source for water quality monitoring data. Data were downloaded from the WQP website using the following query criteria: Country - United States. • Sample Media - Water. • Characteristics - Conductivity, Specific Conductivity, Specific Conductance, Calculated/Measured Ratio. • Date range - 1 January 2000 to 01 November 2019.

The "National Measured Conductivity Data - NWIS" view consists of a shapefile derived from United States Geological Survey (USGS) National Water Information System (NWIS) data. The information displayed is based on measured specific conductivity (SC) data retrieved from the USGS NWIS. NWIS data are based upon consistent, documented sample collection and measurement techniques, as well as consistent data reporting. Data was downloaded for river and stream sampling sites between January 1, 1984 and April 20, 2018. Data collected prior to 1984 were excluded because analytical methods used by USGS prior to that date are less reliable. The downloaded dataset includes more than 1 million water chemistry measurements, collected at 65,698 NWIS sampling stations in the continental U.S. (covering all states and most ecoregions).