In FANFAR, hydrological forecasts and flood risk information are produced using an operational hydrological forecasting and alert pilot ICT system. The core of the system is a hydrological model, whose main function is to predict the effects of meteorological dynamics (e.g. rainfall and temperature) on river flow, water level, soil moisture in rivers, lakes, wetlands, and all land surface areas. In FANFAR, we use the Niger-HYPE model for the Niger River basin and the World-Wide HYPE model for the entire West African domain (http://hypeweb.smhi.se/explore-water/geographical-domains/). Two simulations are carried out to make a forecast with these hydrological models:
- In blue above: A simulation of a historic spin-up period up until the day before the forecast (t<0 → t0, t=time), producing a model state that represents the present hydrological conditions at the start of the forecast period (the initial state, t0). The core input for this simulation is meteorological ‘analysis’ data (i.e. fusion of meteorological observations and models representing historic conditions). Additional observations of the hydrological conditions (e.g. in-situ river flow observations or remotely sensed water levels) are gradually introduced in the system in order to improve the initial state through data assimilation.
- In orange above: A simulation for the forecast period relying on the initial state and meteorological forecast data about future weather dynamics (t1 → t>1). The output of the forecast simulation is a representation of future hydrological conditions.