This mapping webpage evaluates potential groundwater pollution areas for each Ohio county.
The Ohio DNR Hydrologic Atlas provides hydrological data for Ohio that is useful for environmental assessments and planning.
The USGS's Daily Streamflow Conditions dataset includes data on streamflow at 9,936 sites across the United States.
The Streams and Waterbodies of the United States data layer shows the location of water features throughout the United States, Puerto Rico, and U.S. Virgin Islands
The U.S. Environmental Protection Agency (US EPA) is developing e-Estuary, a decision-support system for coastal management. E-Estuary has three elements: an estuarine geo-referenced relational database, associated estuarine and watershed GIS coverages, and tools to support decision-making. A population of 300 estuaries with associated watersheds at the HUC-10 scale (16-100 ha) or larger within the conterminous U.S. has been identified for characterization of estuarine geomorphology, tidal and hydrologic regime, and land-use/land-cover of associated watersheds.