Organization of comprehensive monitoring of embayments in channel reservoirs of Southern Russia using remote sensing data

Abstract

Relevance. Channel-type reservoirs of Southern Russia have undergone substantial transformations throughout their existence as a result of intensive shoreline reworking, sedimentation, and overgrowth by aquatic and semi-aquatic vegetation. Timely assessment of the magnitude and direction of these changes under conditions of strong anthropogenic pressure, climatic instability, and a lack of regular in situ observations is a critical and highly relevant task. Among the most dynamic shoreline segments of reservoirs are bays formed by the inundation of channels and valleys of lateral tributaries of the main river due to backwater effects caused by reservoir impoundment. The transformation of such bays is governed by the combined influence of hydrological, physical, morphological, biological, and other dominant factors. Objective. The objective of this study is to substantiate and develop the structure of an integrated monitoring system for assessing the current geoecological condition of large reservoir bays over the past decade. Methods. The proposed methodology is based on the basin–oriented concept of nature management, which is recognized as one of the most effective approaches to the territorial organization of environmental monitoring. When applied to reservoir bays, this concept makes it possible to identify interconnections and interdependencies between components of the unified geosystem “catchment-main river-estuaries-reservoir”. The ecological condition of reservoir bays is strongly influenced not only by asynchronous and multidirectional water–level fluctuations of the reservoir, but also by the regime and quality of river runoff, as well as the nature and intensity of anthropogenic pressure within the catchment area. The development of the monitoring information blocks was carried out using remote sensing and cartographic methods based on GIS technologies. Results. A structured system of integrated monitoring blocks for bays of channel–type reservoirs was developed, and the methodology for their informational content was tested using the bays of the Tsimlyansk Reservoir as a case study. This paper presents the results of studies conducted for the Novotsimlyansky Bay and the catchments of the Tsimla and Rossosh rivers discharging into it over the Geology and Geophysics of Russian South 16(3) 2026 Геология и геофизика Юга России period 2015–2025. The analysis was based on the combined use of satellite imagery, cartographic materials, GIS technologies, data from the Don Basin Water Authority, and expert assessments. The primary data sources were long–term satellite observations from Sentinel-2A, Sentinel-2B, and Landsat-8/9. Calculated multispectral indices (water and vegetation indices) were used to quantify long-term changes in the bay’s water surface area and the dynamics of its overgrowth. Multitemporal imagery enabled tracing changes in the boundaries of zones subject to variable backwater influence under conditions of maximum and minimum annual reservoir water–level fluctuations.