Evolution of chemical characteristics and irrigation suitability of groundwater in arid and semi-arid regions

Groundwater is a vital resource in arid and semi-arid regions, playing a key role in sustaining ecosystems, supporting agricultural irrigation, and ensuring human survival. This study evaluates the irrigation suitability of groundwater in the Jiefang Sluice Irrigation District, part of the Hetao Irrigation District—the largest single-system irrigation district in Asia. A total of 126 groundwater samples were collected and analyzed to assess chemical environmental changes, classify water quality, and identify the environmental factors influencing the formation of groundwater components during typical irrigation periods. The findings reveal that groundwater in the region primarily falls into two chemical types: Cl-Na and Cl-SO4-Ca-Mg. Analyses of the Water Quality Index (WQI) and irrigation suitability indicate that groundwater quality is poor, with 84.12 % of samples deemed unsuitable for irrigation. This unsuitability is primarily attributed to elevated concentrations of Na+, K+, and Cl⁻. Principal Component Analysis (PCA) and the Gibbs geochemical model suggest that evaporation-induced crystallization and rock salt dissolution are the principal factors contributing to groundwater salinization, whereas processes like silicate hydrolysis and cation exchange are of secondary importance. To ensure the sustainable use of groundwater for irrigation, stricter control measures must be implemented. Key recommendations include optimizing irrigation techniques and promoting ecological restoration to enhance groundwater quality. This study underscores the critical importance of sustainable water resource management in addressing salinity issues and safeguarding groundwater resources, which are indispensable for agricultural sustainability.