Groundwater resources are playing an increasingly vital role in water supply for domestic and irrigation purposes in the Yinchuan Plain, along with the reduction in water transfer from the Yellow River. This study aimed to identify the current status of phreatic water quality and associated hydrogeochemical processes in an irrigated region along the upper Yellow River. A total of 78 water samples were collected in September 2018 for chemical analysis. Results showed that the phreatic water was excellent or good in most areas west of the Yellow River, while it was poor or very poor quality in some places east of the Yellow River. The nitrate contamination is particularly severe in the pluvial-alluvial plain, relating to the localized fine-grained zone with low permeability. Most samples had no sodium hazard but had magnesium hazard. Additionally, the overall evolutionary trend of the phreatic water showed the transformation of Ca-Mg-HCO 3 into Na-Cl-SO 4 type. Rock weathering and evaporation jointly predominate the evolution of phreatic water chemistry. The main geochemical processes involve the dissolution/precipitation of gypsum, halite, dolomite. and calcite, along with the cation exchange. Insights from this work have important implications for groundwater sustainable management in such irrigated regions along the upper Yellow River.

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The water shortage in agriculture area in China requires to reduce the consumption of excessive water in flood irrigation. Therefore, the dynamics of soil water regime is needed to investigate and water‐saving irrigation is necessary to alleviate water shortage. This study investigated the impact of flood irrigation on soil water movement and recharge to groundwater in the Yellow River irrigation area of Yinchuan Plain, China. Combining comprehensive field observation, stable isotopic techniques and water balance simulation, we described the soil water mechanism in vadose zone covered with bare soil in 2019 and planted with maize in 2020. The soil layers affected by precipitation infiltration and evaporation were mainly 0–50 cm, while the soil influenced by irrigation was the entire profile in the mode of piston flow. The maize root took up the soil water up to the depth of 100 cm during the tasseling period. The infiltration and capillary rise in 2020 were similar with those in 2019. However, the total deep percolation was 156.5 mm in 2020 which was about 50% of that in 2019 because of the maize root water uptake. The leakage of ditch water was the major recharge resource of groundwater for the fast water table rise. Precise irrigation is required to minimize deep percolation and leakage of ditch water and reduce excessive unproductive evapotranspiration. Therefore, understanding the soil water movement and groundwater recharge is critical for agricultural water management to improve irrigation efficiency and water use efficiency in arid regions.