Dynamics of overgrowth of the Volgograd reservoir (1972-2018)

The article presents the results of an assessment of the spatial-temporal dynamics of the overgrowth of the shallow waters of the Volgograd reservoir with the aquatic vascular vegetation for the period from 1972 to 2018. It is known that excessive overgrowth may have a significant negative impact on the status of aquatic ecosystems and the conditions of replenishment of commercial fishery. The results of thematic processing of Landsat images received from July to August 1991-2018, and cartographic analysis of overgrowth processes using GIS technologies and comparison with the data of field studies made it possible to identify the features and dynamics of overgrowth for the reservoir as a whole and sites in particular. A general long-term trend was revealed, expressed in the sequential change of two phases of overgrowth of shallow waters of the reservoir. The first phase of slow overgrowth of the reservoir's water area lasted from 1972 to 1991 with an indicator of 0.9% of the area of the water body, the second phase of rapid impulsive overgrowth - from 1991 to 2018 with an indicator of 6.7-10.5 %. At the same time, it was found that the dynamics of overgrowth is largely related to the level regime of the reservoir. The spatial-temporal structure of the overgrowth of the aquatic vascular vegetation of the Volgograd reservoir is characterized by heterogeneity in areas. According to the degree of overgrowth (percentage of the studied area) for the last 5years, the lake (lower) section from the village of Rovnoye to the Volzhskaya HPP dam near the city of Volzhsky is very poorly overgrown - 3.8-4.1 %; the river (upper) section from the Saratov HPP dam to the city of Marks is slightly overgrown - 6.8-8.9 %; the moderately overgrown lake-river (middle) section is from the city of Marks to the village of Rovnoye - 12.0-14.3 %.