Natural river flow provides the conditions required to sustain freshwater ecosystems, and the greater the departure from the natural regime, the greater the loss of those ecosystems. In South America, new hydropower dams are continuously being constructed and planned in regions within and around the Amazon basin and in the Upper Paraguay river basin, a region notable for the Pantanal, a huge wetland ecosystem that is largely dependent on the flow regime of the Paraguay river and its tributaries. In this context, it is meaningful to examine the hydrological changes caused by the major Manso dam, that is operating since 2001 at the headwaters of one of the major tributaries of the Paraguay river. This was done for the same case study by other authors in previous studies using only gauging stations data. However, those previous assessments were limited due to the confounding effects of climate variability and the necessity of relatively long term observed time series. Here, we applied a modeling approach to evaluate the changes in hydrological regime caused by Manso dam operation. Our modeling approach was based on the combination of the MGB large-scale hydrologic model with the SIRIPLAN large-scale wetland model. The models were applied, using river reaches from 2 to 10 km, in two scenarios during the period from 2003 to 2015. In the first scenario we used naturalized streamflow at the dam site as input to the hydrological model. In the second scenario we used observed reservoir outflow time series as input to the hydrological model. Our results show that Manso dam has a regulation effect that decreases high flows, increases low flows and reduces lateral connectivity. The decrease in high flows is more pronounced in the region upstream of the Pantanal floodplain, but not limited to, while increase in low flows extends into Pantanal. Timing of maximum and minimum flows is less affected, except for the river reach immediately downstream of the dam. Our results improve the assessment of spatial patterns of hydrologic alteration, giving more confidence in the assessment of magnitude and spatial extension of the effects of Manso dam in the Pantanal region.

中文翻译：

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上游大坝运行导致南美潘塔纳尔湿地大规模水文变化的模拟评估

自然河流流量提供了维持淡水生态系统所需的条件，偏离自然状态越大，这些生态系统的损失就越大。在南美洲，亚马逊流域内和周围地区以及上巴拉圭河流域不断建造和规划新的水电大坝，该地区以潘塔纳尔湿地而著称，这是一个巨大的湿地生态系统，在很大程度上取决于河流的流态。巴拉圭河及其支流。在这种情况下，检查自 2001 年以来在巴拉圭河主要支流之一的源头运行的主要曼索大坝引起的水文变化是有意义的。这是其他作者在先前研究中仅使用测量站数据对同一案例研究进行的。然而，由于气候变异的混杂影响和相对长期观察时间序列的必要性，这些先前的评估受到限制。在这里，我们应用建模方法来评估由曼索大坝运营引起的水文状况变化。我们的建模方法基于 MGB 大型水文模型与 SIRIPLAN 大型湿地模型的结合。在 2003 年至 2015 年期间的两个情景中，使用 2 至 10 公里的河段应用了这些模型。在第一个情景中，我们使用了坝址的自然河流作为水文模型的输入。在第二种情况下，我们使用观测到的水库流出时间序列作为水文模型的输入。我们的结果表明，曼索大坝具有降低高流量的调节作用，增加低流量并减少横向连通性。高流量的减少在潘塔纳尔泛滥平原上游地区更为明显，但不限于，而低流量的增加则延伸到潘塔纳尔。除了大坝下游的河流河段外，最大和最小流量的时间影响较小。我们的结果改进了对水文变化空间格局的评估，使人们更有信心评估曼索大坝在潘塔纳尔地区的影响的幅度和空间扩展。