The Qualitative Investigation in Terms of Water Type, Drinking and Agricultural Purposes: A Case Study of Semnan Aquifer

Recognizing of groundwater quality، which have the most important role in preparing of the drinking and agriculture water particularly in arid regions، is essential. In this study، the hydrochemical status of Semnan aquifer was drawn and analyzed using qualitative diagrams (Piper، radical، Collins، Schuler and Wilcox diagrams) during August 2008. Then، groundwater quality zonation (water type، drinking and agriculture purposes) were prepared using Arc GIS software. The results showed that the groundwater dominant type is chlorure sodium in Semnan plain. Also، groundwater quality for drinking in northern and northeast and a small area in west of plain is medium to acceptable، and in other regions especially in south and southwest of plain is low. According to Wilcox diagram، the most groundwater resources of the study area located in C4S1 to C4S3 classes. These resources are very saline and almost alkaline water and are not suitable for agriculture. Some groundwater resources in northern and northwestern of plain located in C3S1 and C3S2 classes. These resources are saline water، but can be used in agriculture.