The Dniester river – one of the largest rivers in Europe – flows through territory of two countries: Ukraine and the Republic of Moldova. The flow is formed mainly in upper part of the basin, in Carpathian region, situated in Ukraine. Extreme climatic condition from mountains and boundary plateau generate floods that propagate downstream and cause damage to economy and population. In order to regulate the flood wave, reservoirs were constructed on the stream: two are included in the Dniester Hydropower Complex (DHC) situated at the border of Ukraine and the Republic of Moldova, and the other one is Dubasary reservoir, positioned in the limits of Moldova. Main aim of the research is to evaluate the impact of stream reservoirs on the Dniester floods wave dynamics. The investigations were performed in order to evaluate the changes that occur in flood characteristics for three periods: natural flow, flow regulated by Dubasary, flow regulated by DHC and Dubasary. Based on hydrological time series from stations situated upstream and downstream of reservoirs, there were calculated and compared: flood characteristics, peaks of 10, 5, 1, 0.5 and 0.1% probability, and Environment Flow Components: high-flow pulses, small floods, large floods. The results show that high flood protection is specific to DHC, while through the Dubasary reservoir the flood wave passes mainly in transit. The flood protection system has a greater effect in regulating the floods with medium probability, especially after the DHC construction. The reservoirs caused a slight increase of coefficient of attenuation of peak discharges from 0.30 to 0.40 (in natural conditions) to 0.50-0.60 (in regulated flow conditions). Due to flow regulating impact, small floods as well as their average peaks and duration were reduced in reservoirs downstream part. High-flow pulses increased in number after DHC construction due to hydropeaking effect, however downstream Dubasary reservoirs their reduction is observed. At present, large floods increase in number in the upper part but are transformed into small floods to the downstream, thus protecting the region from inundation. Increasing frequency and occurrence of floods in the Dniester river basin lead to improvement of flood management strategies, both in Ukraine and the Republic of Moldova. In this regard, in the Transboundary Diagnostic Analysis of the Dniester basin the floods and inundations were identified as cross-cutting issue, and, as a result, a set of measures was developed and included in the Strategic Action Program developed and approved at high level in common by both countries.
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Flood wave dynamics in the transboundary Dniester river floodplain under reservoirs impact
Published: 14 March 2023 by MDPI in The 7th International Electronic Conference on Water Sciences session Hydrological Extremes, Hazards and Disasters
Keywords: floods; the Dniester river; reservoirs regulation