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首页> 外文期刊>International journal of river basin management >Modelling the impact of large impoundments on the Lower Zambezi River
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Modelling the impact of large impoundments on the Lower Zambezi River

机译：模拟大型水库对赞比西河下游的影响

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摘要

The Lower Zambezi River is influenced by the presence of two very large hydropower impoundments which have modified the natural seasonal flows, the sediment balance, the morphology of the river and the pattern of the riparian vegetation. Downstream of these large impoundments, appreciable local effects are reported to take place, such as scour, bank collapse and shoreline degradation. In order to quantify the sediment transport along the Lower Zambezi River and to predict the effects of the dams on morphology we have developed a simplified 1-D hydro-morphodynamic model capable to deal with the scarcity of available data. Besides the systematic flow records at the dam gauging station and few occasional measurements of turbidity and grain size of the river bed, only the Digital Elevation Model (DEM) and some recent satellite images of the river have been used as the input data of the model. The results confirm the expected qualitative response of the river to the constructions of dams: the reduction of water flow has an immediate effect downstream of the reservoirs by initially fostering the sediment deposition; afterwards, the total interception of sediment by the dams slowly takes over and inverts this tendency; a smaller aggradation rate with respect to the natural conditions without dams, seems to represent the dominant effect of damming in the long-term evolution of the river. The morphological effects of damming over the transversal cross-section of the river have been studied by a simplified transversal quasi 2-D sub-model, coupled to a 1 -D longitudinal model. Besides the evolution of the bottom longitudinal profile and grain size composition, the model simulates also the evolution of the cross-section shape and the growth of the riparian vegetation. A first application confirms the qualitative observations reported in the literature on the recent planimetric evolution of the Lower Zambezi.
机译：赞比西河下游受到两个大型水电蓄水库的影响，这些蓄水库改变了自然季节性流量，泥沙平衡，河流形态和河岸植被格局。在这些大水库的下游，据报道发生了明显的局部影响，例如冲刷，河岸坍塌和海岸线退化。为了量化沿赞比西河下游的泥沙输送并预测大坝对形态的影响，我们开发了一种简化的一维水力-形态动力学模型，能够处理可用数据的不足。除了大坝测量站的系统流量记录以及河床的浊度和粒度偶尔测量之外，仅数字高程模型（DEM）和一些最近的河流卫星图像已用作该模型的输入数据。 。结果证实了河流对水坝建设的预期质量响应：水流的减少通过最初促进沉积物沉积而在水库下游产生立竿见影的效果。此后，大坝对泥沙的完全拦截缓慢地接管并扭转了这种趋势。相对于没有大坝的自然条件而言，较小的水化速率似乎代表了大坝在河流的长期演变中的主要作用。通过简化的准准二维子模型和一维纵向模型，研究了在河流横断面上筑坝的形态学效应。除了底部纵向轮廓和晶粒尺寸组成的演变外，该模型还模拟了断面形状的演变和河岸植被的生长。第一个应用证实了文献中关于下赞比西河最近的平面演变的定性观察。

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