Hydrogeochemical characteristics, controlling processes, and irrigation suitability assessment of groundwater in the Sanjiang Plain, China

Abstract Groundwater is vital for global irrigation water supply, and its quality directly affects sustainable agricultural development. However, studies on irrigation water quality and its dominant controlling factors in semi-humid regions remain limited. Therefore, taking the Sanjiang Plain as a case, hydrochemical analysis, irrigation water quality assessment, and multivariate statistical methods were employed to systematically reveal the hydrogeochemical characteristics, irrigation suitability, and their dominant controlling mechanisms. The results indicate that the main hydrochemical type of groundwater is HCO 3 -Ca, and most ions exhibit moderate to significant spatial variability. Its hydrochemical composition is mainly controlled by rock weathering, dominated by the dissolution of carbonate minerals, silicate minerals, and evaporite rocks, with significant cation exchange and limited contribution from gypsum dissolution. The groundwater in the study area is generally suitable for agricultural irrigation. However, EC, Na%, RSC, and MH values are relatively high in the Jiansanjiang area in the northeast, while the EC and RSC values are high in the southeast, which poses a potential risk of soil salinization. This spatial variation is mainly controlled by natural geological conditions. Carbonate mineral weathering controls the spatial distribution of MH and RSC. The dissolution of halite and silicate minerals affects variations in SAR and Na% and indirectly influences MH by inhibiting cation exchange processes. RSC shows relatively low correlations with various hydrochemical parameters, indicating that its spatial distribution is regulated by multiple coupled factors. These findings can provide a scientific basis for the rational utilization of groundwater resources, irrigation management, and salinity hazard prevention and control in similar regions.