Determining the minimum environmental flow from dams based on water quality, case study: Taleghan River

Preservation of river ecosystem depends on the quantity and quality of the river flow regime, and the construction of large dams causes quantitative and qualitative changes in downstream rivers, so it is necessary to pay attention to the quality of rivers in addition to the quantity of water needs. Therefore, in this study, a 22 km long section of the river at the bottom of Taleghan Dam located in Alborz Province (103 km of Karaj City) was selected with the aim of determining the minimum flow quantitatively in accordance with aquatic biological standards. Based on this, the average annual and monthly flow of the river in four stations in the study period with an approximate distance of six km from each other was estimated. Since there is a relationship between river hydraulic parameters such as depth and flow velocity with the habitat of the target species (such as the index fish), the measured field value was calculated to determine the optimal habitat conditions. Also, in this study period, to compare the possible change in the concentration of pollutants, each of the water quality parameters with its standard concentration for salmon survival was used as an ecological indicator and it was found that among 17 physicochemical parameters of water quality, Sulfate parameter (SO4) and its concentration can be considered as the most appropriate indicator for determining the minimum environmental flow for red-spotted trout in the Taleghan River. SPSS-24 software and One Sample T Test method were used to determine the mean concentration comparison test with standard concentrations of water quality parameters for Salmon biology.