Effect of Geology on the Chemistry of Water in Meymeh River, West of Iran

Abstract: Aims: The Meymeh River is fed by several tributaries, leading to a gradual decrease in its quality. Considering the construction of the Meymeh reservoir for agricultural use, it is necessary to monitor the spatial and temporal changes in water quality and to identify areas where river quality changes. Methods: Our method was based on the analysis of ۴۲۰ samples over ۱۲ months (۲۰۱۶–۲۰۱۷) in three seasons (low, moderate, and high flow periods) from ۳۵ measuring stations using Spearman's correlation, multivariate statistical analysis, agglomerative hierarchical clustering, and GIS. Findings: The results showed that crossing the saline evaporite layers (especially the Gachsaran Formation) causes a gradual decrease in water quality from upstream to downstream. So, EC reaches from ۴۰۰ to more than ۳۵۰۰ µm. cm-۱ at the confluence of Varazan and Kharvazan tributaries. Besides, the sulfur spring with an average EC of ۲۱۵۹۰ µm. cm-۱ increases EC ۳.۵ times. Siyoul tributary penetrates under the ground after passing through two saline zones and reappears at a distance of ۱۵۰ to ۲۰۰ m with an EC of ۱۸۷۸۰۰ µm. cm-۱. It was also found that about ۵۰% of the salinity of the Meymeh River is caused by the influence of the Ghadah Sulfur Spring and the Siyoul tributary. Conclusion: This study has highlighted some options for managing the level of salinity in the dam. In most cases, one option on its own may not have the desired effect, and a combination of techniques is likely to bring the best results.

کلیدواژه ها:

Gachsaran Formation ، Geological effects ، Meymeh River ، Principle Component Analysis ، Water Quality