The Seymareh reservoir is located in Ilam province. Volume of Seymareh reservoir is about 2500 mcm and the area of upstream basin is about 27000 km2. The main land use of the basin is urban, industrial, agricultural and livestock. The operation of Seymareh reservoir is started from 2011 and this study was defined due to fish kill event during inundation of reservoir at the time of thermal mixing.

This environmental investigation aims at:

• Determination the mail reasons of fish kill event
• Examining the present condition of river and reservoir water quality
• Identification of pollution sources across the basin
• Predicting the river and reservoir water quality at the future using water quality models
• Proposing the mitigation measures at basin and reservoir

Through an extensive environmental investigation and intense fieldwork and water quality sampling, MGCE examined the present condition and predicted the future condition. The performed tasks by MGCE are summarized as follows:

• Preparing studies accomplishment methodology
• Carrying out quantitative and qualitative sampling from of upstream rivers (26 stations) and dam reservoir (4 stations in 5 depths) for about one year (with monthly period)
• Quality modeling of upstream basin along with dam reservoir basin respectively applying SWAT and CE-Qual-W2 models
• Performing TMDL studies for upstream pollutant sources in order to achieving mesotrophic condition in dam reservoir

 Presenting long term and short term solutions for the basin and reservoir