Wetlands usually have been created at downstream of basins and both basin management and use of water in the basin could affect wetlands water quantity/quality. The technical methods on calculating water requirement and the mechanism of allocating water right to wetlands should be considered in the studies. Based on CIWP experience, the process and methodology of calculating Lake Urmia water requirement and discussion on water right allocation system would be presented in the article. The results of this study identified Lake Urmia annual water requirement 3.1 billion cubic meters and the next step would be finding guarantee on water right allocation and operation. To approach this target, we worked on water sharing system between three provinces based on physicochemical and socio-economic indexes.