ASSESSING THE IMPACT OF HYDROPOWER CONSTRUCTIONS AND CLIMATE CHANGES ON FUNCTIONING OF DNIESTER RIVER ECOSYSTEM WITHIN THE HYDROECONEX PROJECT

The HydroEcoNex project is aimed at developing a unified system of innovative environmental monitoring of transformations in the river ecosystems of the Dniester River, caused by the operation of hydropower in the context of climate change. A set of basic parameters was analyzed: a) physicochemical, including temperature and oxygen regimes, sediments, salinity and turbidity, mineralization and water quality (basic ions, nutrients, COD, BOD); b) biological parameters (bacterial, phyto- and zooplankton, fish zoobenthos and fish parasites; c) hydrological parameters (annual and seasonal water reserves in the studied rivers, water level); c) climatic parameters (variability of air temperature and precipitation). Model calculations were carried out using the RegCM4.7 numerical model for the Dniester catchment area. Estimates of the long-term influence of climate on runoff parameters and the state of surface fields of temperature, atmosphere and precipitation were obtained. Expeditionary investigations made it possible to obtain unique data on three-dimensional fields of hydrological and hydrochemical parameters of the Dniester River and Dniester estuary. A statistical analysis of changes in the volume of the Dniester runoff at several representative sites in two intervals comparable in duration was carried out: before the start of the construction of the hydropower complex and after its commissioning.

The general methodology for monitoring the impact of hydropower on transboundary river ecosystems was developed, based on agreed physicochemical, biological and climatic indicators. A comprehensive methodology for the economic valuation of lost ecosystem services was also developed.

The construction of hydroelectric power plants on the Dniester River has led to a sharp deterioration in the state of the ecosystem. These changes include: fragmentation of the continuity of the river, deterioration of the river's ability to self-purify, changes in temperature and oxygen regimes, large fluctuations in water flows and levels, structural changes in bedrock and the annual supply of suspended particles, the rate of mineralization and dynamics of the main ions, the penetration and spread of alien and parasitic species.