In the hydrological sciences, forward-looking analyses such as forecasts, predictions, scenarios, outlooks and foresights are increasingly used for decision-making. These analyses come in many shapes and forms: short-term, long-term, local, global, model-based and scenario-based are but a few of these. Applications are many and include forecasting of floods and droughts, of seasonal availability of water and energy, and prediction for climate change adaptation.

Hydrology for decision-making, however, has an uneasy role as predictive uncertainties may be large: future boundary conditions are unknown, model parameter values may be less than optimal and the system considered may change over time, thus invalidating the model used.

The present session aims to contribute to a better understanding of the role and value, benefit and usefulness of different types of predictions in decision-making, through real-world examples showing both successes and failures.

For the purpose of this session, “predictions” may include different types, e.g. single valued forecasts, probability forecasts, the use of scenarios and outlooks, for different time scales (short-term, medium-term, long-term) and for different spatial scales (from local to regional to global).

Contributions are solicited from scientists, decision-makers and policy analysts in the field of all decision making related to hydrological sciences, including water resources management, natural hazards (e.g. floods and droughts), management of rivers and deltas, and climatic change. Fitting examples from other earth sciences are equally welcome.