Tittle:Assessment of Groundwater Quality and its suitability for irrigationand drinking purpose (A case study: Ardabil Plain, Northwest of Iran)

One of the most important concerns in arid and semiarid regions is the quality of groundwater where it has emerged as super-important source of water for human consumption and agricultural production. This study presents an assessment of methods used to evaluate the quality of groundwater for irrigation and drinking purpose in a semiarid area, Ardabil Plain. Thirty samples of groundwater quality data were collected form observed wells and then data were analyzed for major cations and anions over a period of ten. The result showed that the Na, Ca and Mg were the most domination cations-anions in the groundwater respectively. whereas, in anions the observed order of dominancy was for SO4,HCO3, Cl respectively. A number of quality indices including Ground Quality Index (GQI), Willcox and Schoeller diagrams were applied for Ardabil aquifer to assess the overall groundwater quality of the district. The analyzed GQI, Willcox and Schoeller diagrams showed that groundwater quality in the east and southeast of the study area is suitable for drinking and agriculture usage. According to Wilcox and Shoeller diagrams, available samples were appeared within the classification range of middle and acceptable to good, respectively. The study also revealed that recently the groundwater quality in the study area is decreasing as over-pumpage for irrigation is increasing. This is a case for quality degradation and saline water intrusion in these western areas of Ardabil Plain. Therefore, a degree of protection is needed for this part in order to avoid further transition of groundwater to very poor quality.