The National Water Model (NWM) is a new tool that simulates and forecasts how water moves throughout the nation’s rivers and streams. Running on NOAA’s powerful Cray XC40 supercomputer, the NWM uses data from more than 8,000 U.S. Geological Survey gauges to simulate conditions for 2.7 million locations in the contiguous United States. The model generates hourly forecasts for the entire river network including high-resolution forecasts of soil moisture, surface runoff, snow water equivalent, and other parameters.

The NWM runs in four configurations:

• Analysis and assimilation provides a snapshot of current hydrologic conditions
• Short-Range produces hourly forecasts of streamflow and hydrologic states out to 15 hours
• Medium-Range produces 3-hourly forecasts out to 10 days
• Long-Range generates 30-day ensemble forecasts.

The NWM improves the National Weather Service’s ability to deliver impact-based decision support services nationwide by providing “street level” water information and guidance (e.g., flood maps), as well as serve as the foundation for additional private sector water services. Initially, the model will benefit flash flood forecasts in headwater areas and provide water forecast information for many areas that have not been covered. As the model evolves, it will expand to include water quality forecasts. The NWM also improves NOAA’s ability to meet the needs of its stakeholders (e.g., emergency managers, reservoir operators, floodplain managers, farmers, etc.) with more accurate, detailed, frequent and expanded water information.

The NWM is a cornerstone of the new NOAA Water Initiative, designed to provide more closely integrated water predictive capabilities to promote resilience to water risks. NOAA is seeking to establish an Integrated Water Prediction effort to deliver a suite of more holistic water intelligence products to help communities and industries make better-informed decisions about water management and how to prepare for and respond to extreme water events.