Investigation on the Trophic Status of Ekbatan Reservoir: A Drinking Water Supply Reservoir in Iran

Eutrophication is one of the detrimental environmental problems in water reservoirs dye to the irregular introducing nutrients (phosphorus and nitrogen). This study aimed to explore the eutrophication state of Ekbatan Reservoir, Hamadan, western Iran. Monthly sampling was conducted during April 2010 to March 2011. Seven sampling stations were selected in the various locations of the reservoir and the samples were collected in the depth of 50 cm. The grab sampling of water for nitrogen, phosphorous and chlorophyll-a was carried out at all localities by Hatch sampler. The trophic state of the dam was determined by Carlson''s Trophic State Index (TSI) and Chapra''s classification. The highest concentrations of phosphorus and chlorophyll-a were measured in August and the lowest concentration for both of the parameters was determined in February. The TSI index according phosphorus concentration showed that the reservoir was in eutrophic status during May to November and was in mesotrophic status over November to May. It seems that the eutrophication process in the lake was resulted from the rural wastewaters and agricultural fertilizers. Therefore, using long term management methods including prevent of uncontrolled discharge of agricultural wastewaters is recommended in order to reduce the eutrophication in the reservoir. Decrease of phosphorus concentration in the dam by 50% can convert the eutrophic state to mesotrophic state.