Response Mechanisms and Extreme Hydrological Effects of Runoff Evolution in the Yellow River Estuary Under Climate Change

As the coastal wetlands in the Yellow River estuary are experiencing intensifying degradation and water security challenges are becoming increasingly severe, this study aims to explore the response mechanisms of runoff evolution and extreme hydrological effects in the Yellow River estuary region under the context of climate change. Currently, the degradation of coastal wetlands and water security issues have attracted widespread attention, and understanding the runoff changes and their impacts in this region is of great significance for ecological protection and water resource management. In this study, a surface water model for the study area was established based on the SWAT distributed hydrological model. After parameter calibration and validation, the daily runoff time series from the Lijin Hydrological Station at the basin inlet on the Yellow River was used as the upstream inflow, and its runoff time series was kept unchanged. The evolution process of runoff in the study area under future climate change scenarios was then simulated. Furthermore, the research explored the response relationships between the regional surface hydrological cycle and meteorological factors, as well as the variation patterns of runoff under extreme precipitation conditions.The results showed that: (1) Runoff in the Yellow River Estuary Basin exhibited a positive correlation with precipitation and a nonlinear relationship with temperature. Specifically, runoff increased with rising temperature under constant or decreasing precipitation, but displayed an initial increase followed by a slight decrease with temperature elevation under increasing precipitation. Comparatively, runoff in the Yellow River and its tributaries demonstrated higher sensitivity to precipitation changes. (2) Under extreme precipitation scenarios, daily and monthly runoff variations showed significant fluctuation rates, while annual runoff changes remained relatively smaller.These findings suggest that there are complex relationships between runoff and meteorological factors in the Yellow River estuary region. The results provide critical data support and a scientific basis for rational water resource allocation in wetland ecosystems, facilitating effective protection of wetland environments under flood threats.