Assessment of temporal and spatial eutrophication index in a water dam reservoir

Eutrophication is considered as a serious problem in water reservoirs. Awareness aboutthe eutrophic status of each reservoir could help in providing a better understanding of the problem in aglobal scale. The present study was conducted to assess temporal and spatial eutrophication index in a waterreservoir (Sahand dam) in the northwest of Iran. Physico-chemical parametres that are effective on eutrphiccondition occurrence were analyzed, and trophic state index was calculated on a scale of 0-100 by measuringSecchi disk depth, chlorophyll a, total phosphorus, total nitrogen, total suspended solids, and phosphorus P/Nratio. Moreover, using the overlapping, the reservoir was mapped based on the mentioned index. Seasonalvariation of dissolved solids in the reservoir was recorded due to precipitation and subsequent dilution andevaporation. Thermal stratification was observed during the summer months. The total trophic state indexvalue was calculated as 55.5- 58.07, with minimum value belonging to P/N and maximum value belongingto suspended solids for individual parameters. There were some spatial and temporal differences for trophicstate index in the reservoir. It was found that the whole area of the reservoir was in almost moderatelyupper-mesotrophic condition and in some target stations it was very close to eutrophic condition. The worstcondition was observed in Qaranqu River as the main input to the reservoir. Due to the significant impact ofsuspended particles resulting from erosion of the surrounding lands on TSI value, there is an urgent need formitigation measures to intercept eutrophication.

کلیدواژه ها:

Eutrophication ، Nutrients ، Trophic state index ، Water quality ، Water resource