Thermal regime of the Danube Delta and the adjacent lakes

The Danube Delta is a unique natural object influenced by natural and human factors. According to the available observation and remote sensing data, the features of the water temperature in the Danube Delta, as well as in nearby lakes and the adjacent area of the Black Sea, have been determined. The water temperature in the Danube River was found to be much higher than the air temperature, especially in autumn. Generally, it is also higher than in nearby lakes and the adjacent part of the Black Sea. During 1961–2021 the mean annual water temperature in the Danube Delta increased significantly, especially during the last three decades. It has been determined that water temperature is affected not only by air temperature, but also by water discharge and wind. With a large water discharge the mixing of water is intensified and it causes the decrease of surface water temperature during the main part of the year with the exception of the coldest months. The greatest impact of water discharge on the water temperature is observed in June. The cool breeze in summer months also has some effect on the surface water temperature of the river near the seashore. The results show the potential of remote sensing to track the changes of water temperature along the river and to identify the shallow sections.