Spearheaded by the US Environmental Protection Agency (EPA) and the US Geological Survey (USGS), the National Hydrography Dataset (NHD) is "a comprehensive set of digital spatial data that encodes information about naturally occurring and constructed bodies of water, paths through which water flows, and related entities." The dataset is useful in the creation of maps, in geocoding observations...

The USGS's Toxic Substances Hydrology Program supplies "scientific information to improve characterization and management of contaminated sites, to protect human and environmental health, and to reduce potential future contamination problems." The website features comprehensible articles with links to supplementary materials addressing the latest research findings. Researchers can find information...