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 Groundwater Contours of Michigan dataset includes individual county datasets of the elevation of the water table (first water) encountered every 30 meter across the landscape.
Prospect-R is a web-based decision support tool that helps users determine the feasibility of floodplain restoration efforts. Prospect-R was developed specifically for the restoration of gravel pit mines on the Willamette River, but is ultimately intended to be used more broadly. Maintaining or restoring floodplains helps ensure that these floodplains are able to provide valuable ecosystem services. The connection between river channels and floodplains helps maintain water quality and regulate thermal regimes, which in turn impacts the life cycles of aquatic organisms.
This document provides the goals for New York's state-wide source water assessment program plan to protect sources for New York 10,000+ water systems.
The New England Interstate Water Pollution Control Commission compiles source water assessment for interstate source waters, and provides GIS data. The document provides information on regulation, delineation, inventory, management, contingency planning, enforcement, and progress measurements.
The EPA's DWMAPS is an online mapping tool designed to help concerned citizens and resource managers find information about drinking water in their communities and take action to protect their source water.
Ohio EPA collects and reports information on groundwater quality, and provides data from groundwater monitoring.
The Indiana Department of Environmental Management's Ground Water Section maintains the Indiana Wellhead Protection Program. Indiana's Wellhead Protection page includes information on project implementation and featured communities.