Climate variability and anthropogenic effects on Lake Urmia water level fluctuations, northwestern Iran

Abstract

ABSTRACTLake 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 teleconnections were considered for analysis: the Southern Oscillation Index (SOI) and the North Atlantic Oscillation (NAO). Spectral and coherency analyses were used to recognize the frequency components and the 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 the 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. However, the trend between 1995 and 2009 is negative and it is significant at a 99% confidence interval. This study shows that the very recent fall in water level is due to anthropogenic impacts rather than natural variability.Editor Z.W. Kundzewicz; Associate editor not assigned