Examining the downstream geomorphic impact of a large dam under climate change
Examining the downstream geomorphic impact of a large dam under climate change
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研究气候变化下大坝对下游地貌的影响
DOI：
10.1016/j.catena.2020.104850
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发表时间：
2021
期刊：
影响因子：
6.2
通讯作者：
Kanae Shinjiro
中科院分区：
文献类型：
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作者：
Sanyal Joy;Wesley Lauer J.;Kanae Shinjiro
河流的长期地貌演变既取决于泥沙供应量，也取决于河流输送泥沙的能力。气候变化预计将改变水流频率分布和产沙量，从而可能改变许多受管制河流的地貌轨迹。我们的目标是研究印度戈达瓦里河上游可能的地貌对气候变化的响应，使用两个广为接受的度量：输沙水流频率(T*)和坝下与坝上泥沙通量之比(S*)。利用土壤水分评价工具(SWAT)对流域径流和产沙量进行了模拟。我们使用SWAT-CUP对贾亚克瓦迪大坝下游大坝前(1971-75年)和大坝后(1976-81年)的情况进行了校准和验证。模型的性能良好(流量的NS值为0.6，泥沙的NS值为±10)，不确定性较低(p因子为0.6，r因子为1)，通过将水库调度纳入模拟中，模型的性能得到了显著改善。我们连续10年在大坝前和大坝后的状态下运行该模型，用于根据NEX-GDDP气候预测(排放情景RCP 8.5和4.5)得出的基线(1971-81年)和未来(2090-1999年)气候条件。T*/S*与坝下观测侵蚀量(M)之间的线性关系为估算与未来气候状态相关的侵蚀量提供了依据。我们的模拟显示，在2090年代的情景中，40%的情况下坝址下的T*比基线条件大得多。这可能与与基线相比4-6倍的侵蚀有关。只有在RCP 8.5下才显示严重侵蚀。模拟表明，未来大坝放大的洪峰释放可能会导致更大的下游侵蚀潜力。
Long-term geomorphic evolution of rivers depends both on the amount of sediment supply and on the river’s ability to transport that sediment. Climate change is anticipated to change flow frequency distributions and sediment yield and could thus alter the geomorphic trajectory of many regulated rivers. We aim to examine the possible geomorphic response of the upper Godavari River, India, to climate change using two well-accepted metrics: the frequency of the sediment-transporting flows (T*) and the ratio of the sediment flux below and above a dam (S*). Soil and Water Assessment Tool (SWAT) was used to simulate streamflow and sediment yield in the basin. We calibrated and validated the model using SWAT-CUP for pre- (1971–75) and post-dam (1976–81) conditions downstream of Jayakwadi dam. The model performance was good (NS value > 0.6 for discharge and PBIAS < ± 10 for sediment) with low uncertainty (p-factor > 0.6 and r-factor <1) and it improved significantly by factoring the operation of the reservoirs into the simulation. We ran the model for 10 years consecutively in the pre and post-dam states for baseline (1971–81) and future (2090–99) climate conditions derived from NEX-GDDP climate projections (Emission scenario RCP 8.5 & 4.5). A linear relationship between T*/S* and observed erosion (m) below the dam provided the basis for estimating the amount of erosion associated with future climate states. Our simulations show substantially larger T* below the dam site in 40% of the 2090s scenarios relative to the baseline conditions. These could be associated with 4–6 times the erosion compared to the baseline. Severe erosion is indicated only under RCP 8.5. Simulations suggest that amplified peak releases from dams in the future could lead to greater downstream erosion potential.