Streamflow Forecasts are fundamental to effective operation of flood control reservoirs and levee systems. Forecasts may also support emergency operations by providing estimates of the timing and extent of expected hazardous or damaging flood conditions. Forecasts are based on recent meteorologic and hydrologic conditions in the watershed, and may also incorporate predicted future meteorologic conditions. Although most often used to predict anticipated flood conditions, streamflow forecasts may also support water supply, hydropower, environmental flow requirements, and other operational needs.