Book excerpt: The online National Water Information System (NWISWeb) provides access to more than 100 years of water data collected by the U.S. Geological Survey. The new Web site, NWISWeb: data for the Nation (http://waterdata.usgs.gov/nwis/) allows users to access several hundred million pieces of historical and real-time data. Aggregates all state data into one national database; integrates stream-flow information with many other types of water data, including historic water-quality data from rivers and aquifers, historic ground-water-level data, and real-time water quality, precipitation, and ground-water levels.