Evaluation of surface and ground-water quality of Khar-rud River basin (S Qazvin Province)

Evaluation of water quality is based on some chemical, physical, biological, and radiological characteristics of water and is of great importance for human utilities. One of the chemical characters of water is its salinity (total dissolved salts of water). It may have natural or antropogenic origin. A reason of high salinity of water resources is occurrence of evaporate layers in river watersheds. The aim of this research was investigation of the effect of geological formations on the water salinity of the Khar-Rud River basin. The total area of the basin is 5500 Km2 and 4130 Km2 of this area is located in Qazvin Province. The basin height is 1200- 1680 m above sea level; it is located in the Central Iran Structural Zone. Field studies and physicochemical analysis were done in the the western reach of the basin (from the first tributary in Zanjan Province to Abe-Garm).The results show the Miocene rocks (lithology: mudstone with sandstone and evaporate intercalations) are the main source of the dissolved salts of river water. Water samples were taken in wet and dry seasons of the 2013-14 hydrologic year. The most dominant cation and anion in the river water samples are sodium and chlorine (respectively, Na-Cl type). Salinity significantly increases in the middle segment of the river; it gradually decreases eastward. The groundwater salinity is almost constant. It (associated with the ground water electrical conductivity) gradually decreases eastward.Thehighest salt content of the river water was measured in Dakhrajin, Arvan and Shurab salt mine (53, 45 and 47 g/l, respectively).