Investigating the Effect of Hydroclimatological Parameters on Trend in Variance of Water Level Fluctuations Using Wavelet Transform (Case Study: Urmia Lake)

Water resources and generally natural processes are irregularly distributed in space and time, and they are under pressure due to human activity so it is necessary to understand the relationship between these processes and their impact on each. Urmia Lake is one of the vital hydrological natural quarters of Iran which lately has met sever water level decrease.The drawdown trend of the water level in Urmia Lake poses a serious problem which has had negative impacts on agriculture and industry. In this study wavelet coherence measure is implemented for evaluating the relations and effect of hydrological process over many years on Urmia lake water level fluctuation that is powerful method for testing proposed linkages between two time series. To this end, the strength and relationships between four hydroclimatological variables, including rainfall, runoff, temperature, as well as evaporation and water level fluctuations in the lakes were determined and discussed in terms of high common power region, phase relationships, and local multi-scale correlations. Hydrological data from Saeed Abad station, Ligavn station, Vanyar station and Taze kande Miandoab station are analyzed. The results of the wavelet coherence showed that between the hydrological parameters, runoff parameter has the 23.41% in Saidabad basin, 28.13% in AjiChay basin and 37.57% in Simine basin effect on the Urmia lake water level fluctuations and has the most coherencies (0.9-1) with water level fluctuations in the lake.