4. Calculating hydrometeorological warnings

4.1 General

Warning systems are essentially based on the estimation and forecasting tools described in the previous sections. These warnings can be issued either on the basis of flows, or directly on the basis of precipitation. Both approaches have their advantages and disadvantages. Alerts based on precipitation information alone can be calculated quickly and easily, but they do not directly represent the flow responsible for flooding. Alerts based on flow estimates represent the variable of interest, but the hydrological model on which these simulations are based represents a non-negligible source of error (§ 4.4.2