Evaluation of Ensemble Inflow Forecasts for Reservoir Management in Flood Situations

Abstract

This paper describes the process of analysis and verification of ensemble inflow forecasts to the multi-purpose reservoir of Aguieira, located in the Mondego River, in the center of Portugal. This process was performed to select and validate the reference inflows for the management of a reservoir with flood control function. The ensemble inflow forecasts for the next 10-day period were generated forcing a hydrological model with quantitative precipitation forecasts from the High-Resolution Model (HRES) and the Ensemble Prediction System (EPS) of the European Center for Medium-range Weather Forecasts (ECMWF). Due to the uncertainty of the ensemble forecasts, a reference forecast to be considered for operational decisions in the management of reservoirs and to take protection measures from floods was proved necessary. This reference forecast should take into account the close agreement of the various forecasts performed for the same period as also the adjustment to the corresponding observed data. Thus, taking into account the conclusions derived from the evaluation process of the consistency and the quality of the ensemble forecasts, the reference inflow forecast to the Aguieira reservoir was defined by the maximum value of the ensemble in the first 72 h of the forecast period and by the 75th percentile in the following hours (from 72 to 240 h).