The satellite monitoring of eutrophication processes in a section of the transboundary Argun (Hailar) River using the surface algal bloom index (SABI) according to Landsat remote sensing data

The article is devoted to the monitoring of eutrophication processes in the transboundary section of the Argun River according to Landsat 8 OLI remote sensing data. To assess the impact of intense algal blooms in the water of the Argun River, a 956 km long section from the city of Khailar (China) to the village of Argunsk (Russia) was selected for the time period from May to October 2020, corresponding to the growing season. Based on the analysis of spatio-temporal changes in the surface algal bloom index (SABI), the main areas of eutrophication and time intervals of the greatest deterioration in the quality of the waters of the Argun River were identified. The maximum values of the SABI index indicate the development of algae near the water surface, and low or negative values are an indicator of the development of algae in the deeper layers of the water column, or their absence. It is noted that the SABI index is best suited for assessing the intensity of blooming of river water, which does not have a significant depth, in cases of predominantly superficial concentration of algae. In order to separate the mask of the water surface of the river to ensure the extraction of the SABI index only from the pixels related to the water body, the spectral water index MNDWI was used, the positive values of which indicate belonging to the water surface. To assess the possible sources of algae biomass entry into river waters, a comparative analysis of SABI changes in the system of floodplain lakes along the Argun River – Khara-Nur, Burgat-Nur, Khuretuy, Bara-Nur, Pandza-Nur, Khorubo-Nur, Hulun Lake located in China, was carried out