THE ANALYSIS OF THE DNIESTER RIVER HIGH WATER REGIME (WITHIN THE IVANO-FRANKIVSK AND TERNOPIL REGIONS)
Authors: BARNA Iryna , SOFINSKA Оksana 
Published: November 2022

The Dniester is one of the main cross-border rivers of Eastern Europe. It originates from a source in a forest located in the Ukrainian Carpathians and flows into the Black Sea. The total length of the Dniester River is 1,350 kilometers, and the area of the basin is more than 72,000 square kilometers.

The geological structure of the Dniester basin is complex. In some sections, the channel cuts through rocks of different ages and origins.

One of the characteristic features of the Dniester hydrographic network is the absence of large tributaries and the presence of a significant number of small ones. More than 14 thousand tributaries up to 10 km long. There are also 65 reservoirs and more than three thousand ponds in the Dniester basin. In Ukraine, a hydropower complex has been created from the main and buffer reservoirs and a bulk reservoir on the Dniester. The construction of reservoirs in the Dniester hydropower complex significantly changed the ecological situation in the basin, acting as a barrier to the entry of pollutants in the lower reaches of the river.

The average flow of water in the lower reaches of the Dniester is 311 cubic meters per second, and the average volume of annual runoff is about 10 cubic kilometers. About 60% of the river's annual runoff falls on the summer-autumn period, 25% on the spring period due to snow melting, and 15% on the winter period, which forms mainly through the soil nourishment of the river.

The Dniester belongs to the number of rivers whose water regime is well studied. Observations of the river's water level began as early as 1850. At different times, up to 30 hydrological stations functioned on the Dniester.

A characteristic feature of the Dniester is the high water regime. Every year, up to 5 high waters are observed on the river, during which the water level can rise by 3-4 meters, and sometimes even more. The largest amplitude of the water level fluctuations – up to 9–10 meters – can be observed at the Zalischyky post above the Dniester Reservoir. Maximum water flows pass through the Dniester in both spring and summer, but high water flows are much higher than flood flows.

Floods and high waters are not uncommon in the Ukrainian Carpathians, where the Dniester River originates. Catastrophic high waters in the Carpathians occur once every 30-40 years. Since the beginning of systematic hydrological observations on the Dniester, such high waters have been recorded in 1941, 1969 and 2008. For example, at the Zalischyky post in the Dniester basin, the maximum water flow was 8040 m3/s in September 1941, 5450 m3/s in June 1969, and 5410 m3/s in July 2008. However, at many hydrological stations (Strilky, Sambir, Halych, Nyzhniv, Mohyliv-Podilskyi), it was the last high water that was the highest.

A comparison of the characteristics of high waters in June 1969 and July 2008 allows us to conclude that they were formed under similar synoptic conditions, in the presence of a stationary cyclone over the central and southern regions of the Carpathians, which was characterized by high moisture saturation and a developed system of fronts.

In both cases, a few days before the beginning of the high water formation, intense precipitation was observed, which reduced the water-regulating capabilities of the forest.

Thus, it can be argued that the high water of 2008 is comparable to the high water of 1969.

However, there are some differences. In particular, the feature of the high water in 2008 was not only a significant rise in the water level, but also the high speed of its formation. In three and a half days, the water level in the Dniester rose by more than 6 m.

The 2008 high water caused significant flooding, which could have been even greater without the Dniester Reservoir, which acted as flood control.

For the period of 2010-2021, the years 2010 and 2020 can be noted for their high water level. In these years, high waters due to rainfall were observed on the Dniester, which caused significant material damage, which makes high water forecasting important.

Key words: high water, high water regime, natural hydrological phenomenon, maximum water level values.