No abstract

In recent years, rain floods caused by abnormal rainfall precipitation have caused several damages in various part of Russia. Precise forecasting of rainfall runoff is essential for both operational practice to optimize the operation of the infrastructure in urbanized territories and for better practices on flood prevention, protection, and mitigation. The network of rain gauges in some Russian regions are very scarce. Thus, an adequate assessment and modeling of precipitation patterns and its spatial distribution is always impossible. In this case, radar data could be efficiently used for modeling of rain floods, which were shown by previous research. This study is aimed to simulate the rain floods in the small catchment in north-west Russia using radar- and ground-based measurements. The investigation area is located the Polomet’ river basin, which is the key object for runoff and water discharge monitoring in Valdai Hills, Russia. Two datasets (rain gauge and weather radar) for precipitation were used in this work. The modeling was performed in open-source Soil and Water Assessment Tool (SWAT) hydrological model with three types of input data: rain gauge, radar, and gauge-adjusted radar data. The simulation efficiency is assessed using the coefficient of determination R2, Nash–Sutcliffe model efficiency coefficient (NSE), by comparing the mean values to standard deviations for the calculated and measured values of water discharge. The SWAT model captures well the different phases of the water regime and demonstrates a good quality of reproduction of the hydrographs of the river runoff of the Polomet’ river. In general, the best model performance was observed for rain gauge data (NSE is up to 0.70 in the Polomet’river-Lychkovo station); however, good results have been also obtained when using adjusted data. The discrepancies between observed and simulated water flows in the model might be explained by the scarce network of meteorological stations in the area of studied basin, which does not allow for a more accurate correction of the radar data.

The study presents an assessment of the recent and projected changes of the middle and upper Western Dvina River runoff and regional climate during the 20th and 21st centuries. For this assessment, we used historical runoff data, the output of EURO-CORDEX consortium calculations for scenarios RCP4.5 and RCP8.5, and hydrological model "Hydrograph." Analysis of monthly runoff data for the 1945-2015 period revealed positive trends for each of the five months from December to April. These trends are statistically significant at the 0.05 level. No significant trends were found for other months. Significant negative trends were established for spring flood peak discharges (from −69 to −88 m 3 s −1 per 10 years). Usually, maximum discharges are observed during spring floods. Minimum discharges during winter low-water period were increased by 6 m 3 s −1 per 10 years. The annual runoff trend was statistically significant only at the Polotsk gauging station (9.5 m 3 s −1 per 10 years). To the end of the current century over the study region, estimates of projected meteorological parameters (air temperature and precipitation) show positive tendencies of air temperature (from 2.4 • C to 4.7 • C depending on scenario) and precipitation (up to 15 to 30 mm). Changes of seasonal and annual temperature and precipitation vary depending on the models and scenarios used. The strongest changes were noticed for the RCP8.5 scenario. The greatest changes within each scenario were revealed for the winter and spring seasons. It is projected that during the 2021-2100 period according to both RCP scenarios, annual discharges will not change in the upper part of the Western Dvina River Basin and increase by 10-12% in its lower part. The maximum spring flood discharges in both RCP scenarios are expected to decrease by 25%. The minimum runoff of winter lowflow period is expected to increase by up to 60 to 90% above the present long-term mean values.

In recent decades there has been a trend towards an increase in the number of dangerous hydrological events, especially floods. In order to protect citizens and solve economic problems, it is important to develop and actively introduce into operational practice methods of hydrological forecasting, as well as to build more modern and convenient interfaces of interaction between hydrometeorological services, municipal authorities and citizens. This work discusses a compact automated short-term hydrological forecasting system that uses open-source conceptual models HBV, SimHYD and GR4J as its core. The system is connected to data streams on the observed temperatures and precipitation in the watershed basin, as well as the predicted values of these parameters (in a current implementation, the WRF model with a forecast for 84 hours is used). Also, for operational calibration in daily mode, the system can assimilate (if available) data on observed water levels. Testing of the system is carried out on the example of Tikhvin city (the Tikhvinka river), which in recent years has been characterized by frequent flooding.