Keywords: satellite observations, Kakhovka HPP explosion, river runoff, transitional waters, buoyant plume, marine currents, environmental pollution

A series of satellite images of the Northwestern part of the Black Sea, recorded by the MODIS and VIIRS scanners in the visible range of the spectrum from June 4 to July 1, 2023, were analyzed. Data from operational observations of the river water level and wind and seawater salinity on the Northwestern coast of the Black Sea were also used. A description of the Dnipro water anomalous distribution of in the sea after the Russian occupiers blew up the Kakhovka reservoir’s dam was obtained. Three time intervals and corresponding dynamic modes of the riverine water spreading are allocated. Quantitative indicators of the riverine water dynamics in the sea at the first stage of its expansion are calculated based on the assessment of the average water discharge for 3 days after the dam explosion. It was concluded that the abnormal discharges of the Dnipro (20.5 thousand m3/s) produce an unusual mode of the riverine water dynamics in the sea, namely, the supercritical flow from the Kinburn Strait and the formation of a buoyant plume that interacts with the bottom at a depth of no more than 6 m. According to satellite observations, the plume of turbid riverine waters moved on the shelf at a speed of more than 50 cm/s and quickly reached the Odesa Bay, forming an anticyclonic eddy structure, which later increased to more than 40 km in diameter. As a first approximation, it is accepted that after the dam explosion, about 700 tons of dissolved inorganic phosphorus and more than 1,000 tons of dissolved inorganic nitrogen entered the Black Sea. Such an unusually large amount of nutrients could obviously cause the explosive reproduction (blooming) of phytoplankton. At the qualitative level, the negative environmental consequences for the marine environment of the abnormal input of pollutants and nutrients are outlined.

1. Grishin G.A., Ilyin Y.P. (1983). Variability of oceanographic fields in the northwestern part of the Black Sea based on satellite video data. Methods of the Space Oceanographic Information Processing. Sevastopol: MHI. 78-83. [In Russian]

2. Grishin G.A., Ilyin Y.P., Nelepo A.B., et al. (1984). Interpretation of cosmic images of the sea surface using a digital processing complex SVIT. Earth Exploration from Space, 6. 28-35. [In Russian]

3. Ivanov V.A., Ilyin Y.P. (1995). Atmospheric and hydrological conditions that promote riverine water expansion in the north-western part of the Black Sea. Comprehensive Environmental Studies of the Black Sea. Sevastopol: MHI. 68-81. [In Russian]

4. Ilyin Y.P. (1999). Expansion of the riverine water. Natural conditions of the seaside of the Danube River and the Snake Island. Ivanov V.A., Goshovsky S.V. (eds). Sevastopol: MHI. 5-73. [In Russian]

5. Ilyin Y.P. (2006). Hydrological regime of riverine waters expansion in the North-Western part of the Black Sea. Scientific works of UHMI, 255. 242-251. [In Russian]

6. Ilyin Yu.P. (2022). Average long-term values and variability of water, salt and dissolved nutrient flows in the system of the Dnieper-Bug estuary. Meteorology. Hydrology. Environmental monitoring, 2. 71-80. [In Ukrainian]

7. Ilyin Yu.P. (2023). Average condition and seasonal variability of the structure and dynamics of transitional waters in the Dnieper-Bug estuary region. Ukrainian Hydrometeorological Journal, 32. 63-79. DOI: 10.31481/uhmj.32.2023.05 [In Ukrainian]

8. Ilyin Y.P., Grishin G.A., Bikbaeva R.A. (1986). Salinity Field Variability and Dynamics of the Northwestern Black Sea. Non-Contact Methods and Instruments for the Oceanographic Parameters Measuring. Moscow: Nauka. 171-174. [In Russian]

9. Ilyin Y.P., Grishin G.A. (1988). Summer desalination of the northwestern part of the Black Sea and the possibility of its control by satellite video data. Geographical interpretation of aerospace information. Moscow: Nauka. 119-125. [In Russian]

10. Ilyin Y.P., Repetin L.N., Belokopytov V.N. et al. (2012). Hydrometeorological conditions of the Ukrainian seas. Vol. 2: The Black Sea. Sevastopol: MB UHMI. 421. [In Russian]

11. Tuchkovenko Yu.S., Kushnir D.V., Ovcharuk V.A., et al. (2023). Characteristics of Black Sea dispersion of freshened and polluted transitional waters from the Dnipro-Bug estuary after destruction of the Kakhovka reservoir dam. Ukrainian Hydrometeorological Journal, 32. 95-114. DOI: 10.31481/uhmj.32.2023.07 [In Ukrainian]

12. Carlson R.E. (1977). A trophic state index for lakes. Limnology and Oceanography, 22 (2). 361–369.

13. Gordon H.R. (2019). Physical Principles of Ocean Color Remote Sensing. University of Miami. 995. DOI: 10.33596/ppocrs-19

14. Gordon H.R., Morel A.Y. (1983). Remote Assessment of Ocean Color for Interpretation of Satellite Visible Imagery (A Review). Springer-Verlag, New York. 114. DOI: 10.1029/LN004

15. Hu C., Lee Z., Franz B. (2012). Chlorophyll a Algorithms for Oligotrophic Oceans: A Novel Approach Based on Three-band Reflectance Difference. J. Geophys. Res., 117, C01011. 25. DOI:10.1029/2011JC007395.

16. Oreshchenko A. (2023) Draining of the Kahovka Water Reservoir Caused by the Russian Blowing of the Hydroelectric Plant Dam. International Conference of Young Scientists on Meteorology, Hydrology and Environmental Monitoring (November 15-16, 2023, Kyiv, Ukraine). Ukraine: Kyiv. 34.

17. United Nations Environment Programme. (2023). Rapid Environmental Assessment of Kakhovka Dam Breach; Ukraine, 2023. Nairobi, Kenya. DOI: 10.59117/ 20.500.11822/43696

18. Vyshnevskyi V., Shevchuk S., Komorin V., et al. (2023). The Destruction of the Kakhovka Dam and its Consequences. Water International, published online. 17. DOI: 10.1080/02508060.2023.2247679