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The Yongding River (Beijing, China) was dry most times of the year, and groundwater storage was severely depleted. To address this issue, a river rehabilitation project was initiated. A downstream environmental flow release (EFR) project from upstream reservoirs has been implemented since 2019. This study evaluated the impact of EFR by constructing transient groundwater-flow and numerical tracer transport models to simulate the hydrogeological responses to the water release events in 2019–2020. The study identified two factors that significantly influence the river leakage rate, which are operational factors (i.e., water release rate and duration) and physical factors (i.e., hydraulic properties of the riverbed, regional hydraulic gradients, and groundwater depth) that determine the maximum water availability for groundwater recharge and maximum infiltration capacity, respectively. Predictive modelling was performed to assess the long-term effects of the proposed EFR scheme from 2021 to 2050, which showed that groundwater levels along the river will increase by 10–20 m by 2050. Groundwater storage is expected to be largely recovered and groundwater/surface-water connectivity in the middle reach of the river will be restored. This restoration will not only maintain the environmental flow for the benefit of ecosystems but also enhance groundwater recharge, promoting sustainable groundwater development in the region. Overall, this study provides valuable insights into the effectiveness of the proposed EFR scheme in achieving sustainable groundwater development in the region.

<p>Intensive groundwater exploitation has depleted groundwater storage and led to a series of geo-environmental problems in Beijing Plain, China. To cope with the groundwater depletion problem and achieve sustainable groundwater development, groundwater abstraction has been reduced and Managed Aquifer Recharge (MAR) and Environmental Flow Release (EFR) projects have been piloted and planned. To evaluate the effectiveness of the proposed measures in restoring groundwater storage depletion in Beijing Plain, a 3D transient groundwater was constructed to simulate the effects of these proposed measures regionally and locally. Results show that with the reduction of groundwater abstraction, the declining trend of groundwater level has been stopped. The implementation of MAR and EFR projects have successfully enhanced the groundwater recharge and restored the connectivity of the surface water and groundwater. Prediction model results also show that with the large-scale MAR implementation and current level of groundwater abstraction, groundwater levels and groundwater storage will slowly increase in the next 30 years. With these combined measures in Beijing Plain, sustainable development of groundwater resources is expected to be achieved in the near future.</p>

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