The main aim of the present study was to use different Hydro-Ecological methods to determine the environmental Water Right in a typical perennial river, the Gadar River, the Urmia Lake Basin, Iran for saving Urmia Lake. The ecological needs of the Gadar River were investigated in two different reaches along the river. Three Eco-Hydrological methods (1- FDC shifting, 2- DRM, 3- Q Equation) were used for the assessment of the river environmental flow requirements. In order to maintain the Gadar River at minimum acceptable environmental status (i.e. ClassC of environmental management), average annual flows of 3.28 , 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. The potential monthly flow rates are also proposed in order to preserve the riverine lives. For example, in the Naqadeh Bridge Station, the mean annual flow is proposed 3.28 m3/s, and the monthly flows vary from 0.4 m3/s (in Sept.) to 10 m3/s (in May).
Some more important results that have to be noticed are: 1) Evaluation of Environmental flows for each of the ten rivers entering the Urmia Lake has to be evaluated based on the potential flows from the basin and the upstream reasonable needs and water rights; 2) Monitoring the Environmental flows flowing is necessary along the rivers to make sure that the recipient water body, the Urmia Lake, benefits from the right to be restored; 3) By this way, it is anticipated to provide the Urmia Lake with more than 1 billion cubic meters of water from its 10 surrounding rivers.