Small hydropower (SHP) facilities, defined variably but usually by installed capacities of <10–50 MW, are proliferating around the world, particularly in tropical and subtropical regions. Compared to larger dams, SHPs are generally viewed as having less environmental impact, 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 system located mostly in Brazil. The upland tributaries are important sources of nutrients to the Pantanal, affecting the biological productivity of downstream floodplains. This study presents measurements from upstream and downstream of 25 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 concentrations and transport of nutrients in rivers flowing to the Pantanal. Artificial neural network models estimated the impact of building 80 future SHPs on nutrient transport into the Pantanal, based on observations at current facilities as well as the spatial distribution of future facilities. Overall impacts of current hydropower facilities were not large, and in most cases were indistinguishable based on comparisons between upstream and downstream. The short water residence times of reservoirs associated with SHPs likely explain their tendency to have little or no effect on nutrient transport. However, model predictions for hydropower facilities that may be built in the future, many on rivers with higher discharge and sediment loads, point to significant reductions in overall TN (8%) and TP (29%) transport, with potential negative consequences for river and floodplain productivity. Negative impacts may be either because the rivers carry low nutrient concentrations and are thereby sensitive to oligotrophication, or they are particularly important overall nutrient sources supporting ecosystem productivity in downstream rivers and floodplains. Together with a parallel study of sediment transport, 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 nutrient and sediment supply to the Pantanal.

中文翻译：

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小水电设施的进一步发展可能会改变巴西潘塔纳尔湿地的养分输送

小水电 (SHP) 设施的定义各不相同，但通常安装容量小于 10-50 兆瓦，正在世界各地激增，特别是在热带和亚热带地区。与较大的水坝相比，小水电通常被认为对环境的影响较小，尽管很少有研究支持这一说法。在流入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，潘塔纳尔湿地是世界著名的洪泛区湿地系统，主要位于巴西。高地支流是潘塔纳尔湿地的重要养分来源，影响下游洪泛平原的生物生产力。本研究提供了 25 个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流向潘塔纳尔湿地的河流中养分的浓度和运输。人工神经网络模型根据对现有设施的观察以及未来设施的空间分布，估计了建造 80 个未来小水电对进入潘塔纳尔湿地的养分输送的影响。现有水电设施总体影响不大，多数情况下通过上下游对比无法区分。与小水电相关的水库的水停留时间短可能解释了它们对养分运输几乎没有影响的趋势。然而，对未来可能建造的水电设施的模型预测，许多位于排放量和泥沙负荷较高的河流上，表明总总氮 (8%) 和总磷 (29%) 运输显着减少，对河流和洪泛区生产力有潜在的负面影响。负面影响可能是因为河流营养浓度低，因此对贫营养化敏感，或者它们是支持下游河流和洪泛区生态系统生产力的特别重要的整体营养来源。连同对泥沙输送的平行研究，这些结果支持以下建议，即目前在下游缺乏水坝的几个河流系统应排除在未来的水电开发之外，以维持潘塔纳尔湿地的养分和泥沙供应。对河流和洪泛区生产力的潜在负面影响。负面影响可能是因为河流养分浓度低，因此对贫营养化敏感，或者它们是支持下游河流和洪泛区生态系统生产力的特别重要的总体养分来源。连同对泥沙输送的平行研究，这些结果支持以下建议，即目前在下游缺乏水坝的几个河流系统应排除在未来的水电开发之外，以维持潘塔纳尔湿地的养分和泥沙供应。对河流和洪泛区生产力的潜在负面影响。负面影响可能是因为河流养分浓度低，因此对贫营养化敏感，或者它们是支持下游河流和洪泛区生态系统生产力的特别重要的总体养分来源。连同对泥沙输送的平行研究，这些结果支持以下建议，即目前在下游缺乏水坝的几个河流系统应排除在未来的水电开发之外，以维持潘塔纳尔湿地的养分和泥沙供应。或者它们是支持下游河流和洪泛区生态系统生产力的特别重要的整体营养来源。连同对泥沙输送的平行研究，这些结果支持以下建议，即目前在下游缺乏水坝的几个河流系统应排除在未来的水电开发之外，以维持潘塔纳尔湿地的养分和泥沙供应。或者它们是支持下游河流和洪泛区生态系统生产力的特别重要的整体营养来源。连同对泥沙输送的平行研究，这些结果支持以下建议，即目前在下游缺乏水坝的几个河流系统应排除在未来的水电开发之外，以维持潘塔纳尔湿地的养分和泥沙供应。