Ecological water replenishment through optimal allocation of lake water in water-scarce areas based on channel selection and replenishment period: A case study of China's Baiyangdian Lake

Ecological water replenishment (EWR) greatly improves a lake's hydrodynamics and water quality, and has become a common means of ecological restoration. The replenishment inflow channels, inflow period, and volume allocation are the main factors affecting the benefits of EWR. However, water scarcity often makes it difficult to achieve the optimal EWR allocation. Unfortunately, EWR schemes based on multi-scenario simulation are highly subjective. To develop more objective EWR allocation schemes and fully exploit the available water in areas with a water scarcity, we constructed a two-dimensional hydrodynamic and water quality simulation model for China's Baiyangdian Lake. Using the model, we developed a comprehensive impact index to identify optimal inflow channels for the lake, and determined the EWR period based on the water-level deficit and water quality. By selecting the EWR channels and inflow period, we constructed an optimal EWR allocation model with water quality and water level as the objectives and cost as the constraint. We found that the optimal EWR inflow channels were the Fu, Pu, and Tang rivers, that the lake's EWR period should be from January to April, and that the proportion of water provided by the three rivers to maximize the lake's comprehensive benefits was 62.1 %. The EWR optimization scheme significantly improved the lake's water level and water quality. The model therefore provides important insights for optimizing lake restoration via EWR in areas with a water scarcity.