Verification of the automated flood forecasting system on the Stryi River

The physical and geographical location of the Stryi River Basin causes the formation of catastrophic floods, which are regularly forming in this region and cause significant material damage and, sometimes, the death of people. The last catastrophic flood took place on the Stryi River in June 2020. Thus, the creation of a modern system for forecasting the streamflow of the Stryi River is a very important task. This paper describes such an automated flood forecasting system (FFS Stryi) that is developed at the Ukrainian Hydrometeorological Institute of the State Emergency Service of Ukraine and the National Academy of Sciences of Ukraine. The basis of the system is the hydrological module NAM of the Rainfall-Runoff software complex MIKE 11 (Denmark), which uses the forecasted weather parameters from the numerical mesoscale atmospheric model WRF ARW v. 3.6.1 (USA). The objective of this study is to verify this system and identify the factors that affect the accuracy of flood forecasting of the Stryi River. The system of streamflow forecasting of the Stryi River uses the continuous series of calculated (historical) levels and discharges, air temperature, precipitation, evaporation, as well as the forecast of meteorological indicators for 5 days. The system is set to work with a three-hour time step in the automatic regime. Verification of FFS Stryi according to the historical meteorological data showed that the system reproduces the streamflow of the Stryi River with satisfactory quality. The accuracy of discharge forecasting depends on the accuracy of weather parameters forecasting and, above all, the quantity of precipitation and the time of their falling out. Errors of hydrological forecasting are caused by an imperfect hydrometeorological network of observations (number of points and frequency of measurement), a digital model of the relief of the Stryi River basin and errors of weather parameters forecasts.