USGS National Water Information System (NWIS)

Comprehensive national database of real-time and historical water data from 1.5 million monitoring sites.

The U.S. Geological Survey National Water Information System provides access to water data collected at approximately 1.5 million sites across the country. Data includes real-time streamflow, groundwater levels, water quality measurements, and historical records. The system is essential for watershed planning, flood monitoring, and water resource management in Pennsylvania.