Climate and land use change driving divergent surface water dynamics in the Northern China agro-pastoral ecotone

Northern China’s agro-pastoral ecotone (APE), a semi-arid to semi-humid transitional zone encompassing five major watersheds: Songhua River Basin (SHB), Liaohe River Basin (LB), Haihe River Basin (HB), Yellow River Basin (YB), and Inner Mongolia Endorheic Basin (EB). We integrated high-resolution surface water datasets with hydro-meteorological products and land use records to assess impacts on net water yield ( NWY ). Analysis of surface water dynamics (areas > 1 ha) was conducted using Theil-Sen slope estimation and structural equation modeling. The APE experienced marginally significant hydrological aridification during 1986–2020, characterized by net surface water loss (-4140 ha yr −1 , p = 0.052) and declining water body numbers (-158.7 yr −1 , p = 0.092). Watershed trends exhibited pronounced divergence, with the most severe depletion in the LB (-1523 ha yr −1 and −55.7 water bodies yr −1 ) and moderate declines in the EB (-716 ha yr −1 and −7.2 yr −1 ), contrasting sharply with significant expansion in the YB (1169 ha yr −1 and 46.2 yr −1 , p < 0.001). Major lakes/reservoirs underwent a significant shrinkage, with relative water area ( RWA ) declining at −1.22 % yr −1 ( p < 0.05) and the maximum shrinkage rate in the LB (-3.29 % yr −1 , p < 0.001). A declining aridity index and intensified land use, particularly irrigation expansion and revegetation, amplified evapotranspiration ( ET ), with cropland areas since 2000 showing average ET increases of 1.9 ± 2.6 mm yr −1 (GLEAM) and 6.5 ± 2.5 mm yr −1 (MODIS), thereby diminishing NWY across the APE. These divergent watershed trajectories demonstrate that anthropogenic interventions have outweighed climatic drivers to reconfigure surface water distribution. This human-mediated redistribution of water resources necessitates watershed-specific allocation frameworks to secure regional water sustainability. • Climate-land use shifts drive surface water decline in China’s agro-pastoral ecotone. • Severe water depletion in Liaohe River Basin vs. expansion in Yellow River Basin. • Water-saving irrigation boosted agricultural evapotranspiration in marginal land. • Revegetation-agriculture tradeoffs demand basin-specific water allocation framework.