Evaluation of Groundwater Quality Changes in at the Eastern Plains of Urmia Lake

Groundwater resources are considered as a largest reservoir of available freshwater in the world. According to the importance and scarcity of this precious resource, studying the groundwater quality changes is very important. Declines in water level of Urmia lake has led to increase in the salinity of water in this lake. In this paper, water level reduction effects were studied on qualitative characteristics of groundwater in the eastern part of Urmia lake from 2001-2002 to 2011-2012. With using geostatistical techniques in GIS, TDS &SAR were obtained with Circular, spherical, exponential, and Gaussian semi-variogram models. In most of year Gaussian model with RMSE between 0.44 to 0.94 for TDS and exponential model with RMSE between 0.52 and 1.47 for SAR were selected as the premier models. Groundwater quality changes were evaluated using Co-Kriging interpolation method and qualitative zones were plotted in the eastern aquifer of Urmia lake. The results indicated that water level reduction of Urmia lake had negative effects on the decline of groundwater quality of the eastern plains of Urmia lake. Also, water quality at different points reduced so that TDS varied approximately between 10% and 45% and SAR varied between 7% and 30% during the statistical period.