National Water Model

The National Water Model (NWM) is a hydrologic high resolution model that has the ability to forecast and simulate the rivers and streams flows throughout the entire continental United States (CONUS). The new NWM improves the National Weather Service’s ability to deliver impact-based decision support services nationwide by providing “street level” water information and guidance, as well as serve as the foundation for additional private sector water services. The NWM simulates the water cycle with mathematical representations of the different processes and how they fit together. This complex representation of physical processes such as snowmelt and infiltration and movement of water through the soil layers varies significantly with changing elevations, soils, vegetation types and a host of other variables. Additionally, extreme variability in precipitation over short distances and times can cause the response on rivers and streams to change very quickly. Overall, the process is so complex that to simulate it with a mathematical model means that it needs a very high powered computer or super computer in order to run in the time frame needed to support decision makers when flooding is threatened.

The NWM complements current hydrologic modeling which is done in a simplified manner for approximately 4000 locations across the CONUS by providing information at a very fine spatial and temporal scale at those locations, as well as for locations that don’t have a traditional river forecast.