Evaluation of the Impact of Ecological Water Supplement on Groundwater Restoration Based on Numerical Simulation: A Case Study in the Section of Yongding River, Beijing Plain

Ecological water supplement relies on river channels to introduce surface water, to make a reasonable supplement of groundwater, to repair the regional groundwater environment and urban river ecosystem. Evaluating the degree of groundwater restoration after ecological water supplement (by taking appropriate measures) is a critical problem that needs to be solved. Thus, based on the Yongding River ecological water supplement in 2019 and 2020, we analyzed the groundwater monitoring situates in the ecological water supplement region. We established an unstructured groundwater flow numerical model in the study area through the quadtree grids. The model was calibrated with the measured water level. The simulated results could accurately reflect the real groundwater dynamic characteristics, and it showed that the water level rise was concentrated in the 3–6 km range of the Yongding River after the ecological water supplement. In 2019, the calculated ecological water infiltration amount was 101.28 × 106 m3, the affected area was 265.19 km2, and the average groundwater level rise in the affected area was 2.10 m. In 2020, the calculated ecological water infiltration amount was 102.64 × 106 m3, the affected area was 506.88 km2, and the average groundwater level rise in the affected area was 1.25 m. While the ecological water supplement had a positive impact on groundwater level restoration, the groundwater level around the typical buildings within the study area, including Beijing West Railway Station and Beijing Daxing International Airport, would not be significantly affected.