Investigating the Changes of Dissolved Substances in Water Using Remote Sensing (Case Study: Al-Gharraf River)

Water quality monitoring is important for water resource management, but traditional methods are expensive and limited. Remote sensing provides a practical solution to access accurate information at the lowest cost and in the fastest time. The research aims to study the changes in dissolved materials in the water of the Al-Gharraf River, which is located in the Al-Hay area in Wasit Governorate and is considered one of the main sources of surface water in Iraq. Seasonal data (winter and summer of 2021 and 2022) of water quality parameters collected from the water quality monitoring station in the study area were taken as field observations, and Landsat 8 images formed the remote sensing data for the research. Landsat images were processed using the maximum likelihood classification (MLC) algorithm and water bodies in the area were identified. The performance of MLC was evaluated with precision and precision criteria. The average classification accuracy for the train data was 0.954 and 0.970, and for the test data, they were 0.936 and 0.97, respectively. To detect water bodies, the correlation between six spectral bands, two spectral indices, and 12 different combinations of spectral bands and water quality parameters was calculated using Pearson's coefficient. The results were different depending on the qualitative criteria, but the observed high correlation coefficients showed that the remote sensing data used in the research were useful for monitoring changes in dissolved materials in the water of the Garraf River. The spatial trend of changes was analyzed by the Mann-Kendall test and the temporal trend was analyzed by fifth-order polynomial fitting. The study revealed uniform spatial and seasonal changes in river water quality standards, which affect the environment, aquatic life, and citizens. Landsat satellite data provide valuable information to monitor these changes and help decision makers manage water resources effectively.