Scenario simulation of wetlands restoration in the Yellow River Delta
不同补水条件下黄河三角洲湿地恢复情景模拟

In recent years, a sharp decrease of water quantity and frequent discontinuous flow happened in the lower Yellow River due to the rapid increase of water consumption in the basin area. This leads to deficiency of suitable water demanded by the ecosystem of the estuarine delta. As a result, fresh water wetlands in the delta are diminishing and facing the danger of disappearance. Basic guarantee of water supply to the Yellow River estuary and eco-water demand for wetland restoration has become a key issue in maintaining the ecosystem of the Yellow River Delta. In this paper, landscape ecological and hydrological models were integrated for the Yellow River Delta wetlands restoration. First, three scenarios at different water depths for the degraded wetlands restoration were designed. For each scenario, the spatio-temporal changes of flooding duration and water table were simulated with the model SOBEK, and average groundwater levels were simulated with the finite-difference groundwater flow model Visual MODFLOW. Then the simulation results were integrated with site conditions and current vegetation types into LEDESS model for modeling the landscape development after 5 years of restoration. Finally, each scenario was evaluated based on its consequences for habitat effects. In this way, choices can be made on what kind of nature type is desired and what is the optimal restoration strategy. The results show that all scenarios can significantly improve the wetland conditions of reed marshes, which are used for many rare and endangered birds like red-crowned crane as important habitats. By comparison, scenario B with the medium water discharge is better than scenarios A and C in reed marsh restoration, but scenario C can also create large area of open water bodies which are crucial for the swan's habitat conservation. However, not all kinds of species benefit from the restoration plans. The study also shows that large areas of tidal flats were encroached by the restored reed marshes. As a result, carrying capacity of the estuarine wetlands in shorebirds such as Saunder's Gull would decrease after restoration. This study demonstrates that a spatial decision support framework that integrates hydrological processes modeling with ecological evaluation at a landscape scale is indispensable to evaluate uncertainty about the effects of restoration plans and policies on different wetland types and the quality of waterfowl habitats.