Investigation of Water Quality Impact on Structures of Voshmgir Dam and Its Irrigation Network

This study was aimed to investigate the risk of chemical damages originated from water quality on concrete structures of Voshmgir dam and its irrigation network. In this regard, field survey and water sampling from the dam and its network were carried out in June 2022. In order to determine the intensity of water chemical aggression to concrete, the results of water quality tests were analyzed using soft water aggression indices and well known international standards. Also, the temporal changes of water chemical aggression was investigated using the data received from Golestan water authority. Langelier and Ryznar indices for dam water in June 2021 are -0.6 and 8.6, respectively, and based on these indices, the dam water is corrosive and very corrosive, respectively, and the concrete structure of  spillway is exposed to severe soft water attack. In all studied months, there has been aggression risk of at least one damaging agent to concrete. In December 2021, Ryznar index was 8.49 and the amounts of sulfate and magnesium were 400 and 199 mg/liter, respectively, and there has been a risk of simultaneous aggression by three factors of soft water, sulfate and magnesium. Assessment of water quality of Voshmgir dam in five months showed that the water is corrosive in four months and there is a risk of sulfate and magnesium ions reaction with concrete in two months. So, to protect the spillway’s concrete structure and lining of irrigation canals against leaching by the corrosive dam water and damages originated from reaction of sulfate and magnesium ions with concrete, utilization of epoxy coatings is suggested.