Determination of Environmental Flow Contribution of Gadar River to the Urmia Lake Using Eco-Hydrological Methods

The main aim of the present study was to use different Hydro-Ecological methods to determine the environmental flow requirements in a typical perennial river, the Gadar River, in the Urmia Lake Basin, Iran. The ecological needs of the Gadar River were investigated in two different reaches along the river. Eight Eco-Hydrological methods (1- Tennant, 2- Tessman, 3- Flow Duration Curve Analysis (FDCA), 4- Smakhtin, 5-FDC shifting, 6- DRM, 7- RVA, 8- Q Equation) were used for the assessment of the minimum river environmental flow requirements. In order to maintain the Gadar River at minimum acceptable environmental status (i.e. Class C of the environmental management of rivers), average annual flows of 3.28 and 3.25 m3/s are to be allocated along the river in Naqadeh Bridge and Bahramlu Bridge Stations (located 40 and 18 km upstream from the Urmia Lake), respectively. Also, the prescribed monthly distribution of environmental flow requirements has been considered and proposed for the Gadar riverine life. Restoration of Urmia Lake needs the evaluation of the potential flows from the in-basin rivers and the revision of agricultural water rights. Monitoring the minimum environmental flow regime is necessary along the rivers to make sure the delivery of the water into the Urmia Lake.