Study on hydrochemical characterization and annual changes of surface water quality for agricultural and drinking purposes in semi-arid area

River water can be known as one of the source of water supply in arid and semi-arid regions. One of the important purposes of hydrology is to ensure water supply in accordance with the quality criteria for agricultural, industrial, and drinking water uses. The main objective of this study was to assess the annual changes of water quality in terms of suitability for drinking and agricultural uses in Givdari River, Rafsanjan, Iran. For this purpose, a dataset of monthly averaged values of water quality variables for the Givdari River was prepared for the years of 2001–2010. Result showed that based on the EC and TDS values, the use of river water for irrigation is suitable and acceptable. The pH values were suitable for agriculture and drinking uses in all the studied years. The results also indicated that hazard state with respect to Mg had normal status. According to the correlation coefficient (r), values there are statistically significant (α = 0.01) positive correlations between Cl and Na (r = 0.981), Cl and Mg (r = 0.894), and Cl and SO₄ (r = 0.872). The TDS had good significant correlation with EC (r = 0.999) and all cations and SO₄ and HCO₃ anions at the 0.01 level. The Total Hardness (TH) had good statistically significant correlation with all cations and some anions such as Cl, and HCO₃. According to the hydrochemistry diagrams, the main water types during 10 years based on the frequency were NaCl and NaHCO₃.