Estimation of Ecological Flow of Ghezel Ozan River in Kurdistan Province Using Hydrological Methods

In order to prevent the long-term negative impacts of resource development projects on the riverine ecosystems, it is necessary to define hydrological and ecological needs of river in the form an ecological water-need and consider them in water allocation interactions. The main objective of the present study is to evaluate and estimate the monthly distribution of ecological flow of Ghezel Ozan river by means of hydrological methods, such as Tessman, Tennant, flow-duration curve analysis (FDC), flow-duration curve shifting (FDC-Shifting), Smakhtin and Desktop Reserve Model (DRM), and with reference to the given 25-year statistical period. The results drawn from the present study illustrated that the FDC-Shifting method is superior to other methods due to considering diverse ecological classes, focusing on natural variability of flow, and attempting to maintain this variability in its proposed ecological flows, and in order to maintain the general pattern of flow variability, it employs natural flow-duration curve shift. The abovementioned method is better adapted to the flow potential of Ghezel Ozan river as well as its ecological management method. To preserve Ghezel Ozan river in the minimum acceptable ecological status (ecological management class C), the mean annual flow intensity equivalent to 3.11 (%23 MAR), 1.91 (%22 MAR), 1.43 (%25 MAR), 0.84 (%30 MAR) and 0.28 (%32 MAR) cubic meter per second must be determined respectively within the range of five hydrometric stations including Bianlu, Nesare Olia, Salamat Abad, Hasan Khan, and Shadi Abad.