بررسی روند تغییرات کیفیت آب زیرزمینی دشت میاندوآب با استفاده از روش مان– کندال

Groundwater qualitative changes trend of miandoab plain (in the wet and dry periods) in the period of 1992-2012 was analyzed using the non-parametric modified mann-kendall test for lag-1 autocorrelation cofficient. the results showed that among the 25 sampling stations for 14 water qualitative variables, about 58% of the series had significant (p 5%) increasing trend. also 32% of them showed significant decreasing trends. the remaining 10% of the series exhibited no trend at the 5% significant level. in the case of the wet period 23.7% of the series exhibited upward significant trend and 6.3% of the series had significant decreasing trend at the 5% level. about 70% of the series showed no trend (at 10% significant level). in the dry period, 22% of the series had significant increasing trend (at 10% level), 10% with decreasing trends and 68% of them had no significant trends. the results showed that in the wet period, the steepest increasing trends of groundwater qualitative variables were observed in the west and southern part of the miandoab plain. the declination of groundwater level led to increasing trends for water qualitative parameters in the eastern part of the plain. the results of sen’s slope estimator showed that, the ec and sar had increasing trends for the both dry and wet periods. for example, the trend line slope of the groundwater ec for the wet period was equal to 20 µs cm-1 year-1.