Aiming for globally available but locally relevant seasonal drought risk forecasts with GLOFFIS

An increasing number of countries and river basins worldwide are confronted with droughts. Inevitably, this leads to an increasing pressure on the available water resources and associated drought risks. In order to prevent severe drought impacts, such as food insecurity and possibly even conflicts on water use, timely and focused drought mitigation measures need to be taken. Here, early stage drought forecasts can be of great value, especially when they include local sector-specific information.

Over the past years Deltares developed the Global Flood Forecasting and Information System (GLOFFIS). Up until recent its focus was on floods but now seasonal forecasts have been included to provide drought early warning information. GLOFFIS is based on the wflow framework for hydrological modelling which is embedded within the Delft-FEWS forecast production system that is applied in many countries worldwide.

Wflow relies on so-called pedo-transfer functions that translate input base maps such as land use and soil type to estimate model parameter values. Herewith the model requires little calibration and can easily be implemented for additional basins. The set-up of GLOFFIS is global, yet for the drought forecasting component it was decided to include only high-resolution basin scale models since many global initiatives already exist and the resolution of global models generally lacks granularity to inform decision making. The system is flexible and contains workflows to be easily extended with hydrological models for new basins on demand. The drought forecasts are informed by means of standard drought indicators like discharge anomalies, soil moisture deficit, evaporation deficit indices. This list can be extended depending on the local need. So far hydrological models have been included for the Paraná, Lempa, Rhine and Niger river basins. The application for the Parana will be demonstrated as this basin in South-America currently experiences a severe drought.