River Forecast Centers
The process of forecasting rivers begins with the forecast of the rainfall expected over a period of time. Staff meteorologists prepare a full 5 day precipitation forecast to monitor developing systems.
Every hour staff meteorologists analyze Doppler radar products with measured rainfall from the local gage networks to determine the best estimate of actual rainfall over the region. This estimated rainfall is combined with the 12 hour forecasted rainfall to give the hydrologists an estimate on how much water can be expected to reach a river.
Headwater River ModelingHeavy rainfall will impact any portion of the river, but the most sensitive areas during or immediately following rainfall are the small streams, tributaries, and headwaters that flow into the mainstem rivers. These watersheds react very quickly and cause hazardous flash flooding situations, however these waterways can recede just as fast as they rise creating short term flooding conditions.
Mainstem River ForecastingModeling river flow involves many pieces that must work together to create an accurate forecast. One such factor, soil moisture, is modeled to estimate how much of the rainfall will actually become runoff opposed to remaining in the soil. A second factor is the time it take for the runoff to reach gage 'A'.
Once that is known, the water is routed to next gage (gage 'B') downstream to learn how much runoff and the time it takes to arrive. This flow then combines with the local runoff between gage 'A' and 'B' to create the forecast for gage 'B'. This process continues all the way downstream (e.g., 'A' to 'B', 'B' to 'C', 'C' to 'D', etc.).
Water releases operations from the various reservoirs by the Corps of Engineers, River Authorities, and Water Districts along rivers are also coordinated and incorporated into all forecasts. Additionally, the USGS provides accurate flow and stage observations during flood events for use with the forecasts.
Below is a map of the river forecast centers and their areas of responsibility. Click or select on image below or use drop down menu to go to any office.
The RFC provides hydrologic guidance for time scales that vary from hours (flash flood guidance and support to Local Flood Warning Systems), to days (traditional flood forecasts), to weeks (snowmelt forecasts), to months (seasonal water supply) seen in the figure below.
The RFCs are firmly committed to providing the best possible river forecast guidance to the customers. Improvements come in the form of expanded coverage and increased quality. Efforts are continuously underway to improve the process used to forecast flooding, spring snowmelt, and water supply volumes.