Investigating the causes of rivers discharge reduction to Lake Urmia (Case study: rivers of the south and west of Lake Urmia)

In any country, the management of water resources in watersheds is very important, and managers try to protect these resources by providing management packages. One of the basins that have been considered by managers in the recent years is the catchment area of Lake Urmia located in the northwestern of Iran. In this study, considering the complexity of the rainfall, temperature, evaporation, discharge of hydrometric stations, water volume of the Lake, the contribution of each factor on the rate of decreasing water volume of Urmia Lake was determined. To evaluate the changes in complexity, Wavelet-Entropy combination method was used. To calculate the value of complexity, 41 years seasonal time series were used (period of 1977-2018) for the selected hydrological units of the south and west of Urmia lake. Then, the time series were divided into three equal parts, and the complexity changes were calculated in these intervals based on the wavelet-entropy criterion (SWS). The results showed that SWS of lake water volume, rivers discharge flow and precipitation were reduced in entire time, however, the SWS of temperature and evaporation increased. Generally, it seems that the rivers discharge flow was the main cause of reducing the volume of lake water, and precipitation, temperature, and evaporation parameters were in the next ranks.