The Effect of Evaporative Formations in Increasing the Salinity of the Water Resources in Mahdasht-Eshtehard Region (Iran)

Abstract

Considering the underground water resources salinity problem in Mahdasht to Eshtehard region of southern Alborz Province, we attempted to deal with the relationship between the water sources features especially salinity with the geology of the mentioned range in terms of petrology and structural properties. For this purpose after determining the study range, field investigation was performed to identify the geological formations and the distribution thereof as well as the faults locations using existing geological maps. Using a fourteen year period statistics (2009-2014), the static water table, the discharge rate, annual exploitation and the plain's underground water level elevation (GIS) were analyzed and evaluated. Water samples were taken from 18 wells and chemical analysis determining the quality of water was used. The concentration contour maps of chloride, sulfate, sodium and total soluble solids together with the faults performance analysis showed that the highest salinity concentration relates to northeastern part of the plain. Concentration and qualitative results, the regional water quality can be classified in moderate to disagreeable in terms of potability and saline for agricultural use. The study findings showed that the high evaporative masses' erosion rate and gypsum and saline sediment transport from the northeast Neogene formations have developed saline field in the plain and immethodical exploitation of water sources has considerably reduced the water quality and increased the salinity.