Regulation of the Rule Curve of Dams Based on Conception of Environmental Flow (Case Study: Elected Inflow Rivers to Lake Urmia)

Lake Urmia located in the north-west of Iran has been facing a serious environmental crisis because of some natural and anthropogenic factors. Regulation of rule curve of dams and optimum redistribution of those is essential for conservation the ecosystem of the lake. In a simple hydrological method, optimum flow regime that should be released from dams is estimated by calculation of run off of down stream catchment. In this regards, rule curve of the major reservoir dams (Shahid Kazemi, Shahr Chai, Zola, Derik, Venyar, Ajabshir and Alavian) in the Lake Urmia basin under three different operation policies (30%, 50% and 80% of MAF) has been calculated. Then by using measured data, monthly value of QResidual (the run off of the down stream catchment) has been calculated. In the next step, the term of QAAD (the volume of annual available water in the last station) for each scenario has been determined. The results revealed that by using 80% of MAF (as scenario 3), the value of QAAD would be positive for all the assessed stations; so scenario 3 is selected as effective action for restoration of the lake. Finally for scenario 3, monthly value of QCAH (the nearest hydrograph to natural hydrograph of rivers) in the last station for each rivers and the term of QRW (the monthly volume of water for releasing from dam) have been calculated.