Методика оценки однородности створов мониторинга рек по оптической характеристике водной поверхности — индексу мутности

Abstract

Preservation and improvement of aquatic recourses ecological state is an important state goal. The goal demands monitoring of river discharge and hydrochemical parameters of the river. Only the data allow evaluating of ecologically reasonable anthropogenic impact on an aquatic ecosystem. It is evident that homogeneity of river water at a monitoring river station is the requirement of the monitoring data representativity. Of course, regular control of the homogeneity by each of the identifiable hydrochemical parameters is extremely time-consuming task. The paper presents methodology for check of homogeneity of a monitoring river station by means of Earth remote sensing data analysis. The methodology includes calculation of the Normalized Difference Turbidity Index (NDTI) on the base of Sentinel-2 satellite images in geographical information systems ArcGIS and QGIS within buffer zone of a river section, calculation of distances between cell centers of the NDTI matrix and the initial vertex of the river section (the riverside), the results export in Microsoft Excel files, statistical analysis of the NDTI values homogeneity along the river section. The homogeneity analysis is made by means of the Student and Fisher tests when the NDTI distributions belong the normal law of distribution and by the tests of Wilcoxon-Mann-Whitney and Siegel-Tukey otherwise. The data processing is performed by means a number of workflow models and Python-language programs, a Lazarus-language program, and a number of Mathcad-language programs. The tools are elaborated by Victor Tretyakov. An example of the methodology application is provided in the paper. There is considered evaluation of NDTI homogeneity at the Neva River section located downstream from the Slavyanka River outlet into the Neva River. Of course, the NDTI homogeneity cannot ensure homogeneity of the river section for all the hydrochemical parameters. However, absence of the NDTI homogeneity may serve as a mark of the stream flow non-homogeneity at the river section.