Streamflow drought: implication of drought definitions and its application for drought forecasting

Abstract. Streamflow drought forecasting is a key element of contemporary early warning systems (DEWS). The term streamflow (not forecasting), however, has created confusion within the scientific hydrometeorological community as well in operational weather and water management services. requires an additional step, which application identification method to forecasted time series. way identified main reason for this misperception. purpose study, therefore, provide comprehensive overview differences between different approaches identify droughts European rivers, including analysis both historical implications forecasting. data were obtained from LISFLOOD hydrological model forced with gridded meteorological observations (known LISFLOOD-Simulation Forced Observed, SFO). same fed seasonal forecasts Centre Medium-Range Weather Forecasts system 5 (ECMWF SEAS 5) was used obtain streamflow. analyzed using daily monthly variable threshold methods (VTD VTM, respectively), fixed (FTD FTM, Standardized Index (SSI). Our results clearly show that derived deviate each other their characteristics, also vary climate regions across Europe. VTD) 25 %–50 % more events than (FTM VTM), accordingly average duration longer methods. FTD general, occurrences earlier year VTD VTM. In addition, VTM FTM have higher deficit volumes (about %–30 %) approaches. Overall, characteristics SSI-1 are close what being by outcome illustrated found forecasting, documented 2003 Europe Rhine River specifically. end, there no unique definition (identification method) fits all purposes, hence developers DEWS end-users should agree co-design phase upon sharp type required be specific application.