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

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.

1. Sivohip Zh.T., Pavleychik V.M., Chibilev A.A. Changes in the water regime of the rivers of the Ural River basin. Reports of the Academy of Sciences. Earth sciences, 2019, vol. 488, no. 5, pp. 545–549. (In Russian) DOI: 10.31857/S0869-56524885545-549

2. Gareev A.M. Reki i ozera Bashkortostana [Rivers and lakes of Bashkortostan]. Ufa, Kitap Publ., 2001, 260 p. (In Russian)

3. van Duzer C. Floating Islands: A Global Bibliography. With an Edition and Translation of G.C. Munz’s Exercitatio academica de insulis natantibus (1711). Los Altos Hills, California: Cantor Press. 2004. 404 p.

4. Azza N., Denny P., van de Koppel J., Kansiime F. Floating mats: their occurrence and influence on shoreline distribution of emergent vegetation. Freshwater Biology, 2006, vol. 51, iss. 7, pp. 1286–1297. DOI: 10.1111/j.1365-2427.2006.01565.x

5. Sasser C.E., Visser J.M., Evers D.E., Gosselink J.G. The role of environmental variables on inter-annual variation of species composition and biomass in a subtropical minerotrophic floating marsh. Canadian Journal of Botany, 1995, vol. 73(3), pp. 413–424. DOI: 10.1139/b95-042

6. Sasser C.E., Gosselink J.G., Swenson E.M., Swarzenski C.M., Leibowitz N.C. Vegetation, substrate and hydrology in floating marshes in the Mississipi river delta plain wetlands, USA. Vegetatio, 1996, vol. 122(2), pp. 129–142. DOI: 10.1007/BF00044695

7. John C.M., Sylas V.P., Paul J., Unni K.S. Floating islands in a tropical wetland of peninsular India. Wetlands Ecol Manage, 2009, vol. 17, pp. 641–653. DOI: 10.1007/s11273-009-9140-z

8. Sudd wetland / UNESCO. https://whc.unesco.org/en/tentativelists/6276/ (accessed: 15.07.2022)

9. Biryukov I.N., Markov V.D., Rostokin E.N., Tarunina E.F. Surfacing of peat in reservoirs. Biologicheskie nauki [Biological science]. 1976, no. 3, pp. 94–98. (In Russian)

10. Karpenko L.V. Forecast of environmentally hazardous phenomena in the flooding of Boguchansky marshes reservoir. Geografiya i prirodnyye resursy [Geography and natural resources]. 2009, no. 2, pp. 33–37. (In Russian)

11. Korvet N.G., Spiridonov M.A., Ryabchuk D.V., Sergeev A.Yu., Dron O.V., Sukhacheva L.L. Studies of the Narva reservoir in order to study the formation of peat islands. Gruntovedeniye [Soil science]. 2015, no. 1(6). pp. 36–43. (In Russian)

12. Ryabokon Yu.I., Korpachev V.P., Perezhilin A.I., Andrias A.A., Sladikova S.M. The problem of peat pollution of reservoirs of HPP Siberia. Khvoynyye boreal′noy zony [Coniferous boreal zones]. 2015, vol. 33, no. 1–2, pp. 69–72. (In Russian)

13. Khairisova A.M. Regime of floating islands of Lake Chebarkul of the Republic of Bashkortostan. Geosfera. Sbornik nauchnykh statatey studentov, magistrantov i aspirantov geograficheskogo fakul′teta Bashkirskogo gosudarstvennogo universiteta [Geosfera. Collection of scientific articles of students, undergraduates and graduate students of the Faculty of Geography of Bashkir State University]. 2018, iss. 11, pp. 270–271. (In Russian)

14. Garipov T.T., Gabbasova I.M., Suleymanov R.R., Sidorova L.V., Nazyrova F.I. Optimization of the conditions of composting of the alloy for obtaining organic-mineral fertilizer. Izvestiya Samarskogo nauchnogo tsentra RAN [Proceedings Samara Scientific Center of the Russian Academy of Sciences]. 2013, vol. 15, no. 3 (4), pp. 1250–1253. (In Russian)

15. Gabbasova I.M., Garipov T.T., Galimzyanova N.F., Suleymanov R.R., Komissarov M.A., Sidorova L.V., Himaletdinova G.A. The use of fertilizers based on alloys to increase the fertility of eroded chernozem typical. Agrokhimiya [Agrochemistry]. 2014, no. 6, pp. 35–42. (In Russian)

16. Nemtsev V.V., Kuznetsov A.V. Silver gull Larus argentatus on the Rybinsk reservoir. Russkiy ornitologicheskiy zhurnal [Russian Ornithological journal]. 2021, vol. 30, no. 2091, pp. 3241–3242. (In Russian)

17. Masters B. The ability of vegetated floating Islands to improve water quality in natural and constructed wetlands: a review. Water Practice and Technology, 2012, vol. 7, iss. 1, article number: wpt2012022. DOI: 10.2166/wpt.2012.022

18. Rai D.N., Munshi J.D. The influence of thick floating vegetation (Water Hyacinth: Eichhornia crassipes) on the physico-chemical environment of a fresh water wetland. Hydrobiologia. 1979, vol. 62, iss. 1, pp. 65–69.

19. On Lake Chebarkul, work is underway to repair the dam / Ministry of Agriculture of the Russian Federation. (In Russian) http://old.mcx.ru/news/news/show/18596.htm (accessed: 08.10.2022)

20. Sivohip Zh.T., Pavleychik V.M. Modern trends in the intra-annual distribution of river runoff in the Ural River basin. Proceedings Irkutsk State University. Earth Sciences series, 2020, vol. 33, pp. 112–123. (In Russian) DOI: 10.26516/2073-3402.2020.33.112

21. de Freitas C.T., Shepard G.H., Piedade M.T.F. The Floating Forest: Traditional Knowledge and Use of Matupá Vegetation Islands by Riverine Peoples of the Central Amazon. PLoS ONE, 2015, vol. 10, iss. 4, article number: e0122542. DOI: 10.1371/journal.pone.0122542

22. Pis′ma Pliniya Mladshego [Letters of Pliny the Younger]. Translated by M.E. Sergeenko, A.I.Dovatura and V.S.Sokolov. Moscow-Leningrad, Academy of Sciences of the USSR Publ., 1950, 577 p. (In Russian)

23. Volkova E.M. The Way of Floating Peat Formation in Karst Depressions of European Russia. The Open Geography Journal, 2010, vol. 3, pp. 67–72. DOI: 10.2174/1874923201003010067