Study on the dynamic evolution and driving mechanisms of groundwater in the Northeastern Margin of the Qinghai-Tibet Plateau, China

Groundwater serves as a critical water source for domestic, industrial, and ecological security in valley-type cities across the Qinghai-Tibet Plateau, China. Under the combined pressures of climate change and urbanization, the evolution of regional groundwater systems has become increasingly complex. Taking Xining, a representative valley-type city on the northeastern margin of the Qinghai-Tibet Plateau, as the study area, this study systematically analyzes the dynamic evolution characteristics and driving mechanisms of groundwater based on groundwater depth data from 126 monitoring wells (1980–2025) and multi-source datasets including precipitation, evaporation, temperature, surface runoff, population, economy, land use, and groundwater extraction. By integrating the Mann–Kendall (M–K) test, Grey Relational Analysis (GRA), and Principal Component Regression (PCR), this study reveals the following findings: From 1980 to 2025, the groundwater depth in Xining increased from 10.7 m to 16.2 m before retreating to 13.5 m, undergoing four distinct phases: continuous decline, rapid rebound, dynamic stability, and slow recovery. Concurrently, precipitation and surface runoff exhibited increasing trends at rates of 1.61 mm/a and 0.06 m³/s, respectively, while evaporation decreased at a rate of 11.52 mm/a and temperature showed a slight decline of 0.007 °C/a. Groundwater extraction rose from 0.32 × 10⁸ m³/a to a peak of 2.30 × 10⁸ m³/a before dropping to 1.18 × 10⁸ m³/a. GRA identified groundwater extraction, precipitation, surface runoff, and population as the factors most closely associated with groundwater-depth variation, with relational degrees of 0.862, 0.816, 0.736, and 0.709, respectively. PCR further showed that anthropogenic and natural factors accounted for 59.1% and 40.9% of the relative contribution, respectively. These results indicate that anthropogenic factors provided a greater explanatory contribution to the long-term evolution of groundwater depth during the study period, while natural recharge conditions also played an important role. This study elucidates the stage-specific response patterns and dominant mechanisms of groundwater systems in high-altitude cold valley cities under the combined effects of climatic variability and human activities, providing scientific guidance and theoretical support for sustainable urban groundwater management, ecohydrological restoration, and adaptive water-resource utilization on the Qinghai–Tibet Plateau.