_Applied_  
_sciences_  
_Article_  
**Ecological Conditions of the Lower Dniester and Some**  
**Indicators for Assessment of the Hydropower Impact**  
**[PERSON] 1, [PERSON] 1,*2, [PERSON] 1, [PERSON] 2, [PERSON] 3, [PERSON] 1, [PERSON] 1, [PERSON] 3, [PERSON] 1 and [PERSON] 4,*2**  
Footnote 1: [[https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci)]([https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci))  
Footnote 10: httpsadjacent to Ukraine and Moldova, and a part of the river, running for 437 km, is located in the territory of Moldova. The area of its basin is 72,100 km\({}^{2}\), 26.4% of which is located in the territory of the Republic of Moldova, 0.6% in Poland, and 73% in Ukraine [1,2]. According to the sources of water supply, water regime, and physical and geographical features, the Dniester River basin is divided into three parts:  
* Upper-Carpathian (from the source to the Nizhnee village, the mouth of the river Tlumach, length 296 km).
* Middle-Mohyliv-Podilskyi (from the Nizhnee village to Dubossary, length 715 km).
* Lower (from the dam of Dubossary Hydro Power Plant (HPP) to the mouth, length 351 km) [2].  
The environmental state of rivers is primarily determined by their hydrological regime. At the same time, the Dniester ecosystem has suffered from eutrophication processes as a result of the so-called global \"green revolution\" because of the use of nitrogen and phosphorus fertilizers.  
In the hydrological state of the Dniester River, the following periods may be distinguished:  
* prior to 1954, the natural period without flow regulation and without significant eutrophication, when the hydrological and hydrochemical regimes were formed only under the influence of natural factors. During this period, significant fluctuations in water flow were associated with snow melting and frequent storm floods in the catchment area. Also, there was a time when significant anthropogenic eutrophication was absent.
* 1954-1987, the period of partial flow regulation. This period began while the Dubossary reservoir and the Dubossary hydropower plant (HPP) were put into operation, which led to a decrease in the flow rate and water turbidity. In the 1960s, the process of anthropogenic eutrophication began, and the 1970s were the time of the strong eutrophication impact.
* 1987-2009, when the Dniester reservoir and the Dniester hydroelectric (Dniester HES-1) power station were put into operation. During this period, the hydrological regime of the Dniester middle part was considered fully regulated. As well, the 1980s were a period of extremely high eutrophication levels. The collapse of the Soviet Union in 1991 triggered an economic downturn, followed by a decline in anthropogenic eutrophication.
* Since 2009, when the first hydroelectric unit of the pumped-storage power plant (PSPP) was put into operation, the reservoir is used as the lower reservoir of the PSPP. The morphometric characteristics of the buffer reservoir and the flow regime underwent some changes. Thus, the time since 2009 can be considered as a sub-period of the third (fully regulated) period.  
The aim of our study was to evaluate the current ecological state of the Lower Dniester and to identify the indicators of the hydropower plants' (HPPs) construction impact. For the complex assessment of the current environmental state, we used the data on river hydrology, standard hydrochemistry and pollution of water and bottom sediments, phytoplankton, zooplankton, and macrozoobenthos. The study was carried out under the project with code BSB165 HydroEcoNex.