Climate change impact on water balance of quasi-closed lagoons in the North-Western Black Sea coast

Abstract

The paper studies the impact of regional climate changes that occurred in the past and are expected to occur in the near future on the components of the annual fresh water balance of quasi-closed lagoons in the North-Western Black Sea coast. Currently these lagoons have no permanent connection with the sea. However, there are some episodic connections via artificially created channels, ducts and other waterworks. The value of insufficiency of the studied lagoons' annual fresh water balance is used as an indicator of their ecosystems' sensitivity to climate change. Action plans must be created and implemented for the lagoons that are the most sensitive to changes in regional climatic conditions in order to achieve and maintain their "good" environmental quality status. The climate-induced changes of meteorological parameters in the North-Western Black Sea coast that determine the components of the lagoons' water balance are estimated for two periods: the current one from 2000 to 2018 (based on the observations made at coastal meteorological stations) and the near-future one of 2021-2050 which is compared to the 1961-1990 period (based on the data of the Climate Cadastre of Ukraine). The expected climatic conditions in the near future (2021-2050) were determined by the RCM simulations of the Euro-CORDEX project for the RCP4.5 climate change scenario. The research evaluates the components of the lagoons' fresh water balance (precipitation reaching the lagoons' water surface, fresh water inflow from the catchments, evaporation from the lagoons' water surface) and identifies the residuals (shortages) of annual balance. It uses the "climate-runoff" hydrological model for the above climatic periods to determine the fresh water inflow into the lagoons through the watercourses of their catchment areas. The annual evaporation layer from the lagoons' water surface was evaluated using the long-term average monthly values of temperature and relative humidity for each of the periods. It was established that the climatic changes that occurred earlier and those expected in the current century caused and will cause the increasing insufficiency of the annual fresh water balance of quasi-closed lagoons in the North-Western Black Sea coast. This can threaten salinization, shallowing or even disappearance of some lagoons. Thus new strategies for water and environmental management of such lagoons must be developed. In terms of vulnerability to climate changes leading to significant annual insufficiency of fresh water balance (if there are no other water sources, e.g. water from the sea), lagoons are ranked in the following order: Kuialnytskyi Lagoon, Dofinivskyi Lagoon, Budatskyi Lagoon (if there is no water inflow from the Dnistrovskyi Lagoon), the Tuzla group of lagoons, Sasyk Lagoon, Tyligulskyi Lagoon, Hadzhybeisky Lagoon (if there is no anthropogenic runoff).

Keywords

• the north-western black sea coast
• quasi-closed lagoons
• climate change
• fresh water balance
• insufficiency