Evaluation of environmental river flow estimation methods (case study: Shahrchai River)

Human beings have relied on rivers since thousands of years and have been altering river flows for nearly as long. Therefore, there should be an increasing desire to conserve and restore the ecological health and functioning rivers and their associated ecosystems for human use and biodiversity. To achieve this, it is required to define environmental flow, the flow required in a river to achieve desired ecological objectives. The environmental requirement of the river is the amount of water needed to maintain the ecological conditions and qualitative health of the river water. In this study, to estimate the environmental flow and investigate the effects of the Shahrchai Dam on the Shahrchai River, the average environmental flow of the river was analyzed using the ۱۱-year data with Tennant, Tasman, and Smakhtin methods. The results were obtained at ۰.۸۴, ۲.۱۶, and ۰.۸۵ m۳/s, respectively. Also, the environmental flow was obtained by the PHABSIM habitat simulation method for Black Fish species of ۲.۱۷ m۳/s. Finally, the ۶۸ years of data were used to assess the Dam's influence on the river. The results showed that the flow regime of the Shahrchai River was significantly affected by the Dam's construction and its flow decreased in most months of the year.

Keywords:

Environmental flow , Tennant method , Tasman method , Smakhtin method.