EPA’s Freshwater Explorer is an interactive web-based mapping tool for water quality parameters of freshwater streams, lakes, and groundwater wells in all 50 U.S. states, Puerto Rico, and the U.S. Virgin Islands. It includes both observed data points and estimated background concentrations to make it easy to identify areas where water quality has been impacted by human activities. It can be used by citizens and non-governmental organizations, to better understand national and local water quality issues and to provide water quality information to help federal, state, territory, Tribal, and local partners make decisions about freshwater resources. Users can add spatial layers to explore associations between water quality measurements and natural and human geographical factors and any of the more than 10,000 other available data layers accessible from the GeoPlatform that may affect water quality in the United States.

Freshwater Explorer 2.0, the clean-up procedures, and curated data layers were designed so that states, Tribes, businesses, industries, and everyday American citizens can leverage national data sets to better enable environmental protection empowered by federalism. The work achieves this goal by 1) providing semiautomated clean-up procedures to harmonize data from state and federal sources, 2) providing curated data sets so states are not limited to only their own data, and 3) providing a mapping tool to visualize different kinds of data. These data may be used to characterize background water quality to develop stressor-response relationships or evidence for condition, causal, and risk assessments after taking into consideration application specific data quality needs. These data layers allow states and industry to download the data for analysis, strategic planning, and decision making.