GeoData, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
Engineering and the Environment and Tyndall Centre for Climate Change Research, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
Sci Total Environ. 2018 Nov 15;642:105-116. doi: 10.1016/j.scitotenv.2018.06.006. Epub 2018 Jun 14.
Regular sediment inputs are required for deltas to maintain their surface elevation relative to sea level, which is important for avoiding salinization, erosion, and flooding. However, fluvial sediment inputs to deltas are being threatened by changes in upstream catchments due to climate and land use change and, particularly, reservoir construction. In this research, the global hydrogeomorphic model WBMsed is used to project and contrast 'pristine' (no anthropogenic impacts) and 'recent' historical fluvial sediment delivery to the Ganges-Brahmaputra-Meghna, Mahanadi, and Volta deltas. Additionally, 12 potential future scenarios of environmental change comprising combinations of four climate and three socioeconomic pathways, combined with a single construction timeline for future reservoirs, were simulated and analysed. The simulations of the Ganges-Brahmaputra-Meghna delta showed a large decrease in sediment flux over time, regardless of future scenario, from 669 Mt/a in a 'pristine' world, through 566 Mt/a in the 'recent' past, to 79-92 Mt/a by the end of the 21st century across the scenarios (total average decline of 88%). In contrast, for the Mahanadi delta the simulated sediment delivery increased between the 'pristine' and 'recent' past from 23 Mt/a to 40 Mt/a (+77%), and then decreased to 7-25 Mt/a by the end of the 21st century. The Volta delta shows a large decrease in sediment delivery historically, from 8 to 0.3 Mt/a (96%) between the 'pristine' and 'recent' past, however over the 21st century the sediment flux changes little and is predicted to vary between 0.2 and 0.4 Mt/a dependent on scenario. For the Volta delta, catchment management short of removing or re-engineering the Volta dam would have little effect, however without careful management of the upstream catchments these deltas may be unable to maintain their current elevation relative to sea level, suggesting increasing salinization, erosion, flood hazards, and adaptation demands.
为了保持三角洲相对于海平面的表面高程，需要有规律的泥沙输入，这对于避免盐渍化、侵蚀和洪水泛滥很重要。然而，由于气候变化和土地利用变化，特别是水库建设，河流泥沙输入到三角洲正受到威胁。在这项研究中，使用全球水文地貌模型 WBMsed 来预测和对比恒河-布拉马普特拉-梅格纳、马哈纳迪和沃尔特三角洲的“原始”（没有人为影响）和“近期”历史河流泥沙输送。此外，还模拟和分析了 12 种包含四种气候和三种社会经济路径组合的未来环境变化情景，以及未来水库的单一建设时间表。恒河-布拉马普特拉-梅格纳三角洲的模拟显示，无论未来情景如何，随着时间的推移，泥沙通量都会大幅减少，从“原始”世界的 669Mt/a，到“近期”过去的 566Mt/a，到 21 世纪末的情景中 79-92Mt/a（总平均下降 88%）。相比之下，对于马哈纳迪三角洲，从“原始”到“近期”过去，模拟的泥沙输送从 23Mt/a 增加到 40Mt/a（增加了 77%），然后到 21 世纪末减少到 7-25Mt/a。沃尔特三角洲在历史上的泥沙输送量大幅减少，从“原始”到“近期”过去从 8Mt/a 减少到 0.3Mt/a（减少了 96%），然而，在 21 世纪，泥沙通量变化不大，预计将根据情景在 0.2 和 0.4Mt/a 之间变化。对于沃尔特三角洲，只要不拆除或重新设计沃尔特大坝，流域管理对其影响不大，然而，如果不仔细管理上游流域，这些三角洲可能无法保持相对于海平面的现有高程，这表明盐渍化、侵蚀、洪水灾害和适应需求将不断增加。
