The drainage of mountain tunnels can cause groundwater loss and result in shallow groundwater depletion, which jeopardizes terrestrial vegetation. The impact of tunnel drainage on vegetation can be examined from a physiological perspective using monitoring techniques or evaluated as one item in an environmental assessment of the entire tunnel project. Nevertheless, few previous studies have quantitatively assessed the regional impact of tunnel drainage on plants. We established an assessment framework based on a regionally coupled hydrological model that integrated the tunnel factor into the soil–plant–atmosphere continuum (SPAC) to evaluate the vulnerability status of vegetation threatened by tunnel drainage on a regional scale. The framework comprises five components: (1) a one-dimensional (1D) topsoil model for the vertical unsaturated flow through soil and plants; (2) a three-dimensional (3D) groundwater seepage model delineating water movement between the tunnel and groundwater; (3) a one-way coupling scheme for saturated–unsaturated flow; (4) vegetation-dependent atmospheric boundary conditions representing moisture exchanges between the topsoil and atmosphere; and (5) blockwise vulnerability assessments based on the soil matric potential and vegetation wilting point. The proposed framework was applied to an actual mountain tunnel project. The results showed that the framework can help (i) compare and optimize tunnel design/construction parameters to minimize the impact of tunnel drainage on vegetation, (ii) evaluate the regional impact of long-term/transient drainage of a specific tunnel on plants, and (iii) determine the dominant factor controlling vegetation survival in a given region. Furthermore, the regional impacts of groundwater discharge from the Mingtang Tunnel on vegetation were quantitatively investigated using the assessment framework. It was found that the limited drainage solution of the three typical drainage designs could significantly reduce the area of vulnerable vegetation affected by this tunnel. Groundwater discharge from the Mingtang Tunnel that adopted the limited drainage scheme could harm the growth and yield of vegetation in certain areas, but was unlikely to wither plants, even during drought disasters. In addition, vegetation in this region was more influenced by atmospheric conditions than tunnel drainage. The proposed method can provide a novel perspective and practical assessment tool for promoting environmentally friendly tunnel engineering.

山区隧道的排水会导致地下水流失，导致浅层地下水枯竭，从而危及陆地植被。可以使用监测技术从生理学角度检查隧道排水对植被的影响，或作为整个隧道项目环境评估中的一项进行评估。然而，以前的研究很少定量评估隧道排水对植物的区域影响。我们建立了一个基于区域耦合水文模型的评估框架，将隧道因素整合到土壤-植物-大气连续体 (SPAC) 中，以在区域范围内评估受隧道排水威胁的植被的脆弱性状况。该框架包括五个组成部分：(1) 通过土壤和植物的垂直非饱和流的一维 (1D) 表土模型；(2) 一个三维（3D）地下水渗流模型，描绘了隧道和地下水之间的水运动；(3) 饱和-非饱和流动的单向耦合方案；(4) 代表表土和大气之间水分交换的植被相关大气边界条件；(5) 基于土壤基质势和植被枯萎点的分块脆弱性评估。提议的框架已应用于实际的山地隧道项目。结果表明，该框架可以帮助 (i) 比较和优化隧道设计/施工参数，以最大限度地减少隧道排水对植被的影响，(ii) 评估特定隧道长期/瞬态排水对植物的区域影响，(iii) 确定给定区域内控制植被生存的主导因素。此外，使用评估框架定量研究了明塘隧道地下水排放对植被的区域影响。结果表明，三种典型排水设计的有限排水解决方案可以显着减少受该隧道影响的脆弱植被面积。采用有限排水方案的明塘隧道排放的地下水可能会损害某些地区的植被生长和产量，但即使在干旱灾害期间也不可能使植物枯萎。此外，与隧道排水相比，该地区的植被受大气条件的影响更大。