an assessment of changes in groundwater quality and groundwater levels in lake urmia basin

groundwater quality has a direct impact on human life. the main objective of this research is to investigate changes in groundwater quality and levels in lake urmia basin. tasoj and shiramin plains are selected as a study area. the suitability of groundwater quality for drinking and agricultural purposes were assessed using schoeller and wilcox diagram. according to the wilcox classification, the groundwater of tasoj and shiramin plains fall into c3s1 and c2s4 classification, respectively. based on the schoeller classification, the groundwater of tasoj plain is suitable for drinking, but the concentrations of pollutants are above the permissible limits for drinking, in shiramin. analyzing data from 2003 to 2014, and the parameters like ec, ph, so4, th, tds, mg, ca and cl, showed that the concentrations of these pollutants are increased over time. the correlation of ec and groundwater level decrease, was computed as -0.37, which can mean that the increase in ec is a result of groundwater level reduction. the results showed that the reduction of groundwater quality had an inverse relationship with groundwater withdrawal. every year, underground water level in tasoj decreased about 18cm and the volume of its aquifer is decreased by 1.27 bcm. for shiramin, ground water level and volume increased by 1cm and 0.006 bcm every year, respectively. reduction of groundwater withdrawal in recent years is a result of it’s poor quality. according to the results, the establishment of proper drainage systems to control soil salinity is necessary in study area.