Trend Analysis of Reference Crop Evapotranspiration in Urmia Lake Basin

In this study, the values of ET0 were estimated using the Penman-Monteith method for nine stations located in Lake Urmia basin over the 1986-2010 period. In order to detect the trends of reference crop evapotranspiration (in monthly, seasonal and annual time scales) the non-parametric Mann-Kendall (MK) statistical test was used. The Sen's estimator was used to evaluate the trend line slope of time series. The results showed that in the annual time scale six time series (66.6%) had significant (p