Soil salinity-constrained evolution of cropping structure under climate change and water-saving strategies in an arid irrigation district

Climate change and water conservation demands have posed additional challenges to agricultural management in arid irrigated areas. However, the understanding of the evolution of hydrological processes under multiple environmental stresses, particularly its interaction with soil salinity, remains limited. In this study, we simulated the long-term (2025–2100) evolution of agricultural hydrological processes in China’s Hetao Irrigation District (HID) integrating different climate change scenarios, irrigation-saving strategies, and cropping structure constraints based on soil salinity levels. Under a general trend of increasing temperature and potential evapotranspiration, the cropping structure in the district showed a shift toward more salt-tolerant crops. The most pronounced changes occurring under the SSP370 scenario, a high-emission pathway characterized by strong greenhouse gas forcing. The conversion of maize to sunflower-dominated fields primarily took place during 2025–2050, driven primarily by shallowing groundwater levels, with a mean absolute SHAP value of 0.034. During 2075–2100, gradual soil salinization renders some farmland unsuitable for cultivation, leading to conversion to wilderness land, which mainly attributed to worsening climate conditions and increased evapotranspiration (ET). The Jiefangzha sub-irrigation area, characterized by shallow groundwater table and current maize dominance, experienced the most significant changes in cropping structure. Under the current irrigation regime (achieving 60% desalination rate during non-growing season), the agricultural land area remained stable, but irrigation demands increased, particularly under high-emission scenarios. Maintaining a non-growing season desalination rate above 55% preserves soil salinity stability, and helps slow the decline groundwater levels, whereas a desalination rate below 50% severely threatens cropping structure resilience. Although these simulations are based on assumed conditions, these findings offer insights for management in arid regions facing the dual challenges of climate change and resource scarcity.