Small hydropower (SHP) facilities, which are defined by installed capacities <10–50 MW, are increasingly being built around the world. SHPs are viewed as less environmentally harmful than larger dams, although there has been little research to support that assertion. Numerous SHPs have been built, and many more are in development or proposed, in rivers that drain into the Pantanal, a world-renowned floodplain wetland. Three river systems with the largest contributions of sediments to the Pantanal—the Cuiabá, upper Taquari, and Coxim rivers—remain largely undammed. The upland tributaries transport sediments into the Pantanal, thereby affecting geomorphological dynamics and biological productivity of downstream floodplains. This study presents measurements from upstream and downstream of current hydropower facilities, most of which are SHPs, throughout the upland watersheds of the Upper Paraguay River basin to reveal how these facilities may affect the transport of suspended sediments and of bedload sediments. In addition, a predictive model using artificial neural networks (ANNs) estimates the impact of building 80 future SHPs on sediment transport based on observations at current facilities as well as the spatial distribution of future facilities. More than half of current facilities retained suspended sediments: 14 of the 29 facilities showed >20% net retention of suspended sediments, two others retained between 10 and 20%, seven were within 10%, and six showed >10% net release. Bedload sediment transport was a small component of total sediment transport in rivers with high total sediment loads. Multiyear series of satellite images confirm sediment accumulation in several cases. Model predictions of the impacts of future hydropower facilities on suspended sediment concentrations and transport show retention of a large fraction (often much >20%) of sediment inputs. Summing riverine transport rates for inflows into the Pantanal indicates that currently envisioned future hydropower development would reduce the suspended sediment transport by ∼62% from the current rate. This study shows that if SHPs are built on sediment-rich rivers, this may prove problematic for the facilities as well as for downstream ecosystems. These results support recommendations that several river systems presently lacking dams in their lower reaches should be excluded from future hydropower development to maintain the sediment supply to the Pantanal.

中文翻译：

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小水电设施的进一步发展将显着减少向巴西潘塔纳尔湿地输送的泥沙

小水电 (SHP) 设施的定义是装机容量 <10-50 MW，正在世界各地越来越多地建造。与大型水坝相比，小水电被认为对环境的危害较小，尽管很少有研究支持这一说法。在流入世界著名洪泛区湿地潘塔纳尔湿地的河流中，已经建造了许多小水电，还有更多正在开发或拟建。对潘塔纳尔湿地沉积物贡献最大的三个河流系统——库亚巴河、塔夸里河上游和科西姆河——基本上没有大坝。高地支流将沉积物输送到潘塔纳尔湿地，从而影响下游漫滩的地貌动态和生物生产力。本研究介绍了当前水电设施上下游的测量结果，其中大部分是小水电，整个上巴拉圭河流域的高地流域，以揭示这些设施如何影响悬浮沉积物和底床沉积物的运输。此外，使用人工神经网络 (ANN) 的预测模型基于对当前设施的观察以及未来设施的空间分布，估计了建造 80 个未来小水电站对泥沙输运的影响。超过一半的现有设施保留了悬浮沉积物：29 个设施中有 14 个显示悬浮沉积物的净保留量 >20%，另外两个保留在 10% 到 20% 之间，7 个在 10% 以内，6 个显示 >10% 的净释放。底泥输沙是总输沙量高的河流中总输沙的一小部分。多年系列卫星图像证实了几种情况下的沉积物积累。未来水电设施对悬浮泥沙浓度和运输影响的模型预测显示，大部分（通常>20%）的泥沙输入被保留。将流入潘塔纳尔湿地的河流输送速率相加表明，目前设想的未来水电开发将使悬浮泥沙输送比当前速率减少约 62%。这项研究表明，如果小水电建在富含沉积物的河流上，这可能会给设施以及下游生态系统带来问题。这些结果支持以下建议，即应将目前在下游缺乏水坝的几个河流系统排除在未来的水电开发之外，以维持对潘塔纳尔湿地的沉积物供应。未来水电设施对悬浮泥沙浓度和运输影响的模型预测显示，大部分（通常>20%）的泥沙输入被保留。将流入潘塔纳尔湿地的河流输送速率相加表明，目前设想的未来水电开发将使悬浮泥沙输送比当前速率减少约 62%。这项研究表明，如果小水电建在富含沉积物的河流上，这可能会给设施以及下游生态系统带来问题。这些结果支持以下建议，即应将目前在下游缺乏水坝的几个河流系统排除在未来的水电开发之外，以维持对潘塔纳尔湿地的沉积物供应。未来水电设施对悬浮泥沙浓度和运输影响的模型预测显示，大部分（通常>20%）的泥沙输入被保留。将流入潘塔纳尔湿地的河流输送速率相加表明，目前设想的未来水电开发将使悬浮泥沙输送比当前速率减少约 62%。这项研究表明，如果小水电建在富含沉积物的河流上，这可能会给设施以及下游生态系统带来问题。这些结果支持以下建议，即应将目前在下游缺乏水坝的几个河流系统排除在未来的水电开发之外，以维持对潘塔纳尔湿地的沉积物供应。