Empirical Detection of Turbid and Clear Water Using Space-Borne Sentinel-2Case Study: Sefidrud Dam

The effects of clear and turbid water on the contribution of prefitons, which play an important role in aquatic nutrition and in the treatment of contaminated waters, are very important in a way that is more abundant in clear waters than opaque waters. In this paper, using Sentinel-2 measuring images and using spectral properties of opaque and clear water, and emphasizing statistical quantities, they are to be detected in the Sefidrud Dam during two seasons (March 27 , 2017) and summer (September 13, 2017). In this regard, after applying the required preprocesses (geometric and radiometer correction), by examining the spectral behavior curve of these two phenomena as well as the OIF index, optimal color combinations were detected by the test and error method. Accordingly, the most suitable color combination contains the largest amount of information for the spring, the color combination (a4,8,8) and for the summer, the color combination (8.1, a8) was determined. On the other hand, using the spectral-velocity study of opaque and clear water, within the range of 4/0 – 87/0 μm (bands 1 through a8), these two phenomena are well-differentiated from each other and other phenomena. Therefore, the NDVI index, which examines the standardized difference of the near-infrared spectral range (band 8) and visible red (band 4), was considered for revealing cloudy and transparent water, and eventually, by applying thresholds on it, Cloudy and clear water was distinguished from each other.