New datasets on daily precipitation deficit from 2025-2060 have been developed and released by the STARS4Water for each of its seven River Basin Hubs. Precipitation deficit is a common measure for severity of agricultural drought. The precipitation deficit addresses the need for drought monitoring, which was expressed by several STARS4Water stakeholders,  including the Drammen, East Anglia and Danube basin stakeholders.

Precipitation deficit D is defined as the accumulated difference between precipitation P and (potential) evaporation ET. Both P and ET are daily absolute values. As daily evapotranspiration for future years was not readily available, we decided to calculate it from incoming radiation and air temperature, which are available from climate and energy related variables from the Pan-European Climate Database derived from reanalysis and climate projections. The Priestley-Taylor formula was used to calculate daily (potential) evaporation. From daily precipitation and (potential) evaporation, we calculate the precipitation deficit by taking the sum of the daily differences (evaporation minus precipitation) from April 1st up to the current date. If the precipitation deficit turns negative, we reset it to zero.

Drought severity can be assessed by taking the maximum value per season (April-September). The precipitation deficit is an accumulated index, which takes into account both the intensity and the duration of water scarcity. Low precipitation and high evaporation over a longer period of time will build up a large deficit. Note that the precipitation deficit is based on the potential evaporation. The actual evaporation will be reduced by limited availability of water in vegetation and the soil.

All newly derived data has been uploaded to Zenodo (https://zenodo.org/records/15240491)

Derived from data from https://cds.climate.copernicus.eu/datasets/sis-energy-pecd

For more information, visit the following page of the STARS4Water Github Organization: https://zenodo.org/records/15240491