Evaluation of groundwater salinity in Guilan plain according to effective salinity and potential salinity

In addition to surface water resources, groundwater resources supply the urban, industrial and agricultural demands. So its quality should also be considered in addition to its quantity. To assess the quality of groundwater, some parameters should be considered where salinity is the most important. The purpose of this study was to identify and characterize areas in Guilan plain with certain salinity levels of groundwater for agricultural purposes. Thus, the water samples were collected from 130 wells across the Guilan province, in September 2008 and concentrations of Ca2+, Mg2+, HCO3-, SO42-, CO3-, Cl- and electrical conductivity (EC) were measured. Then geostatistical analysis of data with GS+ software was performed. Finally, the critical areas of Guilan plain in terms of groundwater salinity were identified for agricultural purposes, and proper strategies for groundwater were proposed. The electrical conductivity of central and eastern areas is between 1-1.5 dS/m, being critical for rice cultivation. Also in this area, average potential salinity and average effective salinity range from 3 to 15 mmol/lit which is a warning for the future of groundwater resources.