Integration of policy assessment and Budyko framework: Understanding hydrological evolution in semi-arid inland lake basin under climate change and human activities

The Dai Lake (2305 km²) located in Ulanqab City of Inner Mongolia's semi-arid region, representing typical inland lakes under severe water stress globally. This study integrates the Budyko framework with policy assessment to quantify climate change and human activity contributions to hydrological evolution (1970–2023). Using Mann-Kendall trend analysis, mutation detection, and elasticity coefficient methods, we identified 2002 as a critical transition point and analyzed meteorological variables, land use changes, and socio-economic factors impacting runoff processes while evaluating recent water management policies. The closed basin experienced dramatic changes since the 1970s: lake area decreased from 164.11 to 45.46 km² with 12.28 m water level decline. Human activities dominated hydrological changes (-84.24 %) versus climate impacts (-15.76 %). The runoff-precipitation relationship changed fundamentally after 2002, with slope decreasing from 0.12 to 0.04, indicating weakened response to intensive water consumption. Agricultural water use was the strongest negative driver (r = -0.84, p < 0.01). Policy interventions since 2014 showed measurable effectiveness, reducing livestock from 730,000 to 320,000 and shifting human contribution to positive (91.92 %) in 2020–2023. Despite improvements, water structure remains imbalanced with 85.08 % groundwater dependence and only 7.26 % ecological allocation, highlighting needs for sustained policy implementation in semi-arid inland lake systems. • Developed a Budyko-based method combining policy-driven analysis to separate climate and human impacts. • Built quantitative links between watershed hydrology and human activities via elasticity framework. • Revealed compound climate effects on hydrological processes from a multivariate perspective. • Proposed an ecology-oriented strategy for optimal water resource management in arid basins.