DataSheet1_Spatiotemporal Impact on Vegetation by Tunnel Discharging in the Jinping II Hydropower Station: Evidence From the NDVI and GPP Monitoring Dataset of 2001–2019.docx

An impact on vegetation by tunnel discharging has been a critical point for underground constructions around the world. The Jinping II hydropower station in China possesses the world’s largest karst diversion tunnel group and discharged massive groundwater during the construction period. This study assessed the effects on vegetation in the karst and non-karst areas at different stages before construction (2001–2003, BC), during construction (2004–2014, DC), and after construction (2015–2019, AC) based on the Normalized Difference Vegetation Index (NDVI) and the gross primary productivity (GPP) dataset of the moderate resolution-imaging spectroradiometer (MODIS). The regional median results of the NDVI and GPP showed that the whole vegetation was little changed by massive tunnel drainage throughout BC, DC, and AC. The NDVI and GPP were locally decreased in the first 3 years, and then recovered to the original level within next several years. Notably, the NDVI and GPP of the karst area (20 and 50% in the total area) were decreased more significantly than those of the non-karst area (8 and 20% in the total area). The factors controlling vegetation change are the development of karst and fractures, which are the conduits of groundwater flow. Therefore, massive groundwater discharge is the primary influence leading to the vegetation deterioration in the Jinping II hydropower station. The research would provide a vital reference for vegetation protection of large-scale underground construction in the world.

隧道排水对植被的影响已成为全球地下工程建设领域的关键研究议题。中国锦屏二级水电站拥有世界规模最大的岩溶引水隧洞群，施工期间排放了大量地下水。本研究基于中分辨率成像光谱辐射计（MODIS）的归一化植被指数（Normalized Difference Vegetation Index, NDVI）与总初级生产力（Gross Primary Productivity, GPP）数据集，评估了施工前（2001–2003年，BC）、施工期（2004–2014年，DC）及施工后（2015–2019年，AC）三个阶段内，岩溶区与非岩溶区的植被受影响情况。NDVI与GPP的区域中位值结果显示，在BC、DC、AC全阶段中，大规模隧道排水并未对区域整体植被造成显著改变。仅在前3年局部区域的NDVI与GPP出现下降，随后在数年内恢复至原有水平。值得注意的是，占总面积20%与50%的岩溶区，其NDVI与GPP的下降幅度显著高于占总面积8%与20%的非岩溶区。控制植被变化的核心因素为岩溶与裂隙发育，二者为地下水径流提供了运移通道。因此，大规模地下水排放是导致锦屏二级水电站植被退化的主要诱因。本研究可为全球范围内大型地下工程的植被保护提供重要参考依据。