Mapping of water turbidity of the Strizhen River in the city of Chernihiv using images of the Sentinel-2 satellite mission

Abstract

This article is devoted to the development and justification of the methodology for automated monitoring and mapping of water turbidity of small rivers in urbanized areas using the example of the Stryzhen River in the city of Chernihiv, Chernihiv region, using remote sensing (RS) data. The object of study was selected as reservoirs No. 2 and No. 3 of the Stryzhen River within the administrative boundaries of the city of Chernihiv, which do not have appropriate research and, according to visual observations, have significant anthropogenic loads over the past 15 years due to the development of residential areas. The spectral channels of the Sentinel-2 satellite (B2, B3, B4, B8) for the period from 2017 to 2025 were analyzed. The paper proposes the algorithm for processing spatial data in the Google Earth Engine environment, which includes performing preliminary cloud filtering, subpixel resampling to a resolution of 10 m. To obtain cartographic materials, automatic separation of the water surface was performed using the normalized differential humidity index (NDWI) and an assessment of the spatial heterogeneity of the distribution of suspended solids based on the turbidity index (NDTI). As a result of the study, it was found that the riverbed is optically heterogeneous: in the northern part of reservoirs No. 2 and No. 3 (Yalivshchyna ditsrict), persistent anomalies of high turbidity were detected, which indicates the processes of siltation, shallow water and eutrophication in stagnant zones. Taking into account the obtained mapping results, it will be determined that the use of satellite information to overcome the discreteness of classical ground-based hydrochemical monitoring of narrow and regulated water bodies.