Tropical river basins have experienced dramatically increased hydropower development over the last 20 years. These alterations have the potential to cause changes in hydrologic and ecologic systems. One heavily impacted system is the Upper Paraguay River Basin, which feeds the Pantanal wetland. The Pantanal is a Ramsar Heritage site and is one of the world's largest freshwater wetlands. Over the past 20 years, the number of hydropower facilities in the Upper Paraguay River Basin has more than doubled. This paper uses the Indicators of Hydrologic Alteration (IHA) method to assess the impact of 24 of these dams on the hydrologic regime over 20 years (10 years before and 10 years after dam installation) and proposes a method to disentangle the effects of dams from other drivers of hydrologic change using undammed “control” rivers. While most of these dams are small, run-of-the-river systems, each dam significantly altered at least one of the 33 hydrologic indicators assessed. Across all studied dams, 88 of the 256 calculated indicators changed significantly, causing changes of 5–40%, compared to undammed reaches. These changes were most common in indicators that quantify the frequency and duration of high and low pulses, along with those for the rate and frequency of hydrologic changes. Importantly, the flow regime in several undammed reaches also showed significant alterations, likely due to climate and land-use changes, supporting the need for measurements in representative control systems when attributing causes to observed change. Basin-wide hydrologic changes (in both dammed and undammed rivers) have the potential to fundamentally alter the hydrology, sediment patterns, and ecosystem of the Pantanal wetland. The proposed refinement of the IHA methods reveals crucial differences between dam-induced alteration and those assigned to other drivers of change; these need to be better understood for more efficient management of current hydropower plants or the implementation of future dams.

中文翻译：

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大坝引起的潘塔纳尔河流域水文变化

在过去的 20 年中，热带河流流域的水电开发急剧增加。这些变化有可能导致水文和生态系统发生变化。一个受到严重影响的系统是上巴拉圭河流域，它为潘塔纳尔湿地提供水源。潘塔纳尔湿地是拉姆萨尔湿地，是世界上最大的淡水湿地之一。过去20年来，巴拉圭上游流域的水电设施数量增加了一倍多。本文使用水文变化指标 (IHA) 方法评估了 24 座大坝在 20 年（大坝安装前 10 年和安装后 10 年）对水文状况的影响，并提出了一种将大坝的影响从使用未设坝的“控制”河流的其他水文变化驱动因素。虽然这些大坝中的大多数都是小型的河流系统，但每座大坝都显着改变了所评估的 33 项水文指标中的至少一项。在所有研究的大坝中，256 个计算指标中有 88 个发生了显着变化，与无坝河段相比，造成了 5-40% 的变化。这些变化在量化高低脉冲频率和持续时间以及水文变化速率和频率的指标中最为常见。重要的是，几个未设坝河段的流态也显示出显着的变化，这可能是由于气候和土地利用的变化，支持在将原因归因于观察到的变化时在代表性控制系统中进行测量的需要。流域范围内的水文变化（在有坝和未筑坝的河流中）有可能从根本上改变水文，潘塔纳尔湿地的沉积模式和生态系统。拟议的 IHA 方法改进揭示了大坝引起的变化与分配给其他变化驱动因素的变化之间的关键差异；需要更好地理解这些，以便更有效地管理当前的水力发电厂或实施未来的大坝。