The dynamic patterns of groundwater storage in Horqin Sandy Land are driven primarily by climate factors but threatened by human activity

Horqin Sandy Land (HQSL), a typical agro-pastoral transition zone in northern China. This study assessed groundwater storage anomaly (GWSA) in HQSL under climate change and human activity, using Gravity Recovery and Climate Experiment (GRACE) satellite data, Global Land Data Assimilation System (GLDAS) models and in-situ well observations. Herein, Mann–Kendall test, Empirical Orthogonal Functions (EOFs) and Partial Least Squares Structural Equation Modeling (PLS-SEM) model were applied to analyze the seasonal and long-term trend changes of GWSA and quantify the process of GWSA in HQSL. HQSL was divided into sandy plain of intensive water use (Zone I) and mountain of water source (Zone II). GWSA from GRACE fitted well with in-situ data ( r² = 0.65, p < 0.01 ). GWSA declined at −0.15 ± 0.12 mm/yr from 1985 to 2002 derived by in-situ observation wells and at −7.79 ± 0.87 mm/yr from 2002 to 2020 evaluated by GRACE. The decline was more pronounced in Zone I (−5.04 ± 0.23 mm/yr) than in Zone II (−3.84 ± 0.18 mm/yr) from 2002 to 2020. Monthly variations peaked in June (−30.78 mm), mitigated by precipitation in August (−8.10 mm) from 2002 to 2020. Spatially, GWSA loss intensified after 2013, particularly in northern mountains. Climate factors consistently influenced GWSA while growing human activity impacts intensified after 2010. These findings provide valuable insights for locals to mitigate climate change impacts through optimization of human activity, as water-saving land use strategies. • Plains show more pronounced groundwater storage variations than mountains. • Climate factors reversed the impact on groundwater storage after 2010. • Human activity increasingly impacting groundwater storage in agro-pastoral zone.