Landscape‐hydrological phenomenon of the formation of floating islands on Lake Chebarkul (Davletovo) in the Ural River basin, Russia

Abstract

Aim. To record factually the development of floating islands on Lake Chebarkul (Davletovo) as a landscape‐hydrological phenomenon in the Ural River basin and in the Southern Trans‐Urals, to determine the mechanisms of formation and to identify the specific features of their morphostructure, intra‐annual movements and long‐term dynamics.Materials and Methods. Based on images of high (2003–2020) and medium (1972–2020) spatial resolution, an analysis was made of qualitative and quantitative indicators reflecting the long‐term and intra‐ annual dynamics of the state of floating islands (mats) and coastal thickets of macrophytes («splavina» or «labza» in Russian).Results. It was established that the main source of material for the islands were the coastal thickets of macrophytes at the site of the confluence of watercourses into the lake (Yangelka River and Mogak Crrek), which periodically (during periods of extreme spring floods) lose contact with coastal shallow waters and are carried into the lake. The high variability of the states and the dynamism of the displacement of the islands, as well as the tendency to reduce the number and area of the islands and coastal thickets of macrophytes, caused, among other factors, by the consequences of the anomalous summer flood of 2013, were revealed. Being in an unfixed state, floating islands drift along the water area of the lake for considerable distances, reaching 10–15 km or more during the ice‐ free period of the year. The main driving force is the wind, which causes prevailing alongshore displacements of the islands: as a result of collisions, they are reduced in size and acquire a rounded shape in plan.Conclusion. Throughout the historical period, floating islands around the world have been perceived as a landscape phenomenon that deserves protection and rational use. Lake Chebarkul with floating islands is of undoubted interest as an object of geographical, hydrological, ecological and biological research.