Overgrowing of the Ivankovskoye reservoir and its influence on hydro-ecological processes in the reservoir

The Ivankovskoye Reservoir is the oldest and shallowest of the reservoirs of the VolgaKama Cascade. Over the almost 90 years of the reservoir's existence, its water area has become significantly overgrown with higher aquatic vegetation, which occupies about 26% of the reservoir area and more than 55% of the shallow water area. The objectives of the research included a comprehensive longterm study of the dynamics of overgrowing of the Ivankovskoye Reservoir, its current trends and an analysis of the environmentforming role of macrophytes as a factor in hydroecological processes in the reservoir. Archival materials, aerial video and aerial photography were used for the research, and since 1990, annual field work has been carried out. It has been established that in recent decades the low water level in the reservoir, as a result of climate change, contributed to the creation of favorable conditions for the rooting of Phragmites communis Trin. and the spasmodic overgrowing of coastal shoals. A further rise in the water level did not lead to degradation of the thickets. An even more pronounced change in the structure of the vegetation cover of the Ivankovskoye Reservoir is the existence of individual plants in the reservoir until 2008, and then the mass spread of the species Trapa natans L. This species was not previously found in the reservoir, and currently occupies almost the entire water area of the stagnant bays of the rightbank part of the Ivankovskoye Reach of the reservoir with a continuous carpet. Macrophytes directly and indirectly affect all processes within the reservoir. They significantly slow down the speed of water movement and water exchange, affect the chemical composition of water, are soilforming material and affect the composition, condition and properties of bottom sediments, as well as ice phenomena. Macrophytes create isolated ecological niches, which contribute to the development of bluegreen algae.