Hydrochemistry and stable isotopes study of the precipitation at Haraz Basin, north of Iran

Stable isotopes (Deuterium and Oxygen-18) have a broad application in many of water related sciences. Precipitation is the most important input to the water cycle which shows considrable spatial and temporal variability in its isotope content. To study the precipitation isotope content, 51 samples from August 2015 to July 2016 have been collected mainly on a monthly basis with few events based samples at five stations in Haraz basin, north of Iran. A local meteoric water line (LMWL) of the Haraz basin is expressed by the equation δD=7.66δ18O -8.48‰. Both slope and interception of LMWL are lower than corresponding values for the Global Meteoric Water Line (GMWL). The isotope composition of precipitation generally shows a seasonal fluctuations and it has been influenced by rainfall amount and ambient air temperature. Considering the precipitation chemistry at Haraz basin shows that the Ca^(2+)and HCO_3^- are the main ionic species accounting for 70.8% of total ionic concentration. Total ionic concentration shows a seasonal trend of lower values in wet and higher concentrations at the dry months. The absence of strong correlation between ion species, suggests that precipitation’s chemistry affected by crustal elements, marine salt and anthropogenic activities.