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Lake Urmia, the second largest hyper-saline lake on earth, has recently experienced a dramatic water level reduction. This could have been caused by climate change or other anthropogenic effects; however it could also be a part of natural climate variability. To explore the hydroclimate variability effect on the lake water level, two tele-connections were considered for analyses; Southern Oscillation Index (SOI) and Northern Atlantic Oscillation (NAO). Spectral and coherency analysis were used to recognize the frequency components and relationship between the teleconnections and the lake water level fluctuations. The results show that the recent water level fall and the rise of water level in 1994-1999 cannot be explained by natural periodic behavior of Lake Urmia. The inter-decadal water level oscillations are coherent with NAO and SOI components of such oscillations. The anthropogenic effect on the lake water level was also explored using non-parametric trend analysis. The results show that the lake water level has a positive trend between 1966 and 1995, but the trend is not significant at a 95% confidence level.On the other hand, the trend between 1995 and 2009 is negative and it is significant at a 99% confidence interval. This study shows that the very recent water level fall is due to anthropogenic impacts rather than natural variability.

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