Role of flow naturalization in estimating environmental flow by hydraulic and hydrological approaches

Determination of the environmental flow of rivers using hydrological and hydraulic methods has received more attention due to the available information and less cost and time. The important point in using these methods is to consider the natural conditions of the river by eliminating the effect of upstream withdrawals. To investigate the necessity of naturalization of the flow and its effect on determination of the ecological water supply of Zayandehroud river at the location of the Sad-e-tanzimi station (before major drinking, industrial and agricultural harvests) and Varzaneh station (near Gavkhuni wetland and after harvest and water infiltration) has been selected as a case study. Based on the Tennant method, using the observed and naturalized flows at Varzaneh station, the ecological watercourse showed that if the observed flows are used, it will obtain about 0.6 cubic meters per second. It turned out that there would be practically no water flowing in the river. If naturalized flow is used, 16 percent of the basin runoff potential will be allocated to the environment. The environmental flow obtained from the wetted perimeter method with the curved slope algorithm at the Sad-e-tanzimi and Varzaneh station has estimated 13 and 16 percent of the annual average natural flow, respectively, which is within the acceptable results of the modified Tennant method. Has been located. As a result, the use of the modified Tennant method is recommended due to the ease of calculating and providing the monthly distribution of environmental water, provided that the naturalized flow time series is used at the study stations.