Spatiotemporal Investigation of Maroon dam effects on water quality by multivariate statistical Analysis

Maroon River is a valuable aquatic ecosystem in Iran. The purpose of this research was to investigate the lasting impacts of the Maroon dam on river water quality (RWQ), particularly downstream, and determine those factors affecting the optimal management of the RWQ. The modified Mann-Kendall and Sen's slope estimator tests were employed to investigate the variation trend of qualitative parameters. Then, multivariate statistical analyses, including correlation assessment, cluster analysis, T-test, and factor analysis of spatiotemporal pattern, are applied to recognize factors affecting the effects of dam construction. Results showed that the total hardness and the calcium, chlorine, and sulfate concentrations significantly increased in downstream at a level of 5%</em> confidence. The cluster analysis indicated that dam construction probably did not affect the upstream; however, the increased dissolution rates of calcium and sulfates downstream illustrated the presence of the Gachsaran formation in the river path and the dissolution of rock gypsum in the water. The factor analysis determined three and two main components before and after dam construction with 84.8%</em> and 71.6%</em> variances, respectively. These components and the correlation between chloride-sodium and calcium-sulfate ions could show the Sodium Chloride  dissolution and the effects of the dissolution of gypsum mid-layers from the Gachsaran formation after the dam construction. The strong relationship between the magnesium and chlorine contents in the Cham Nezam station might result from the salt/detergent-contained household and urban wastes entering the river. According to the results of various tests, the dam has changed the quality of the river downstream. Still, Wilcox and Schoeller's indices demonstrated that dam construction did not significantly affect the RWQ used for drinking and agriculture.