Detection of Precipitation fluctuation on surface runoff in Urmia Lake

The aim of this study was to investigate the effects of changing precipitation in Debi on the Urmia Lake’s surface. Calculation and analysis on the Urmia basin’s average rainfall and discharge is performed. In this study, a 42-year period from 1345 until 1386 took place for precipitation factors and Debbi. We used the SPI model to identify precipitation fluctuations and drought periods and then using Spearman correlation test the relationship between precipitation and Debi in different stations were displayed. Graphical diagrams analysis shows that fluctuations in rainfall caused swings in Debi and in those years that SPI model shows a drought the average flow rate in Debi reduces the average level prevailingand based on phases of increasing and decreasing rainfall in between 1365-1385, Debi was impacted by these phases. Lands intense rainfall and its effect on runoff caused a mutation in Man Kendall test and this model also shows the reduction rate in Debi. This mutant formed in 1374 and has continued until the end of the study period. By reducing the amount of precipitation the standard deviation and average Debi in flow stations was reduced and linear equation in forward rates was declined and the decline has continued until today.