LAUSR

Irrigation water quality is of great concerns to the sustainable agriculture and often is neglected in most irrigation areas in Ordos Basin, a semi-arid area in China. In this paper, a hydrochemical investigation of groundwater was performed to highlight the groundwater quality and evaluate its risk/suitability for irrigation purpose in Ordos Basin. Hydrographical method, Piper diagram and PHREEQC geochemical modeling were employed to characterize the groundwater quality and the relevant geochemical processes. Electrical conductivity, sodium percentage (Na%), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), permeability index, magnesium ration (MR) and Kelley’s ration (KR) were used to evaluate the suitability for irrigation purpose. In summary, 86.67% of the area is fresh water (TDS < 1 g/L) with HCO 3 type, brackish water (1 g/L < TDS < 3 g/L) with HCO 3 , SO 4 , HCO 3 ·Cl, Cl·SO 4 type and salt water (TDS > 1 g/L) on the northwest side of the study area with Cl–Ca·Mg·Na type. The distribution of nitrate contents showed that nitrate pollution is a persistent problem that affects a wide area of the aquifer. The calculated Na%, SAR, RSC, MR and KR indicate that most of the groundwater is of acceptable risk for irrigation as well as for domestic usage. The Gibbs plot showed that the hydrochemistry of groundwater samples was mainly influenced by evaporation–precipitation and water rock dominance including carbonate and silicate minerals weathering.