Abstract To support eco-friendly hydropower planning in developing regions, we propose a spatial optimization model for locating dams to balance tradeoffs between hydropower generation and migratory fish species richness. Our model incorporates two special features. First, it is tailored to the dispersal of tropical migratory fishes, which typically require long, unimpeded river stretches to complete their life-cycle. To model fish with this type of dispersal pattern, we introduce the concept of a river pathway, which represents a novel way to describe river connectivity. Second, it combines decisions about dam placement and removal, thus facilitating opportunities for hydropower offsetting. We apply our model to the Sao Francisco River basin, Brazil, an area of hydropower-freshwater biodiversity conflict. We find that dams have reduced weighted migratory fish richness 51% compared to a pre-dam baseline. We also find that even limited dam removal has the potential to significantly enhance fish biodiversity. Offsetting the removal of a single dam by the optimal siting of new dams could increase fish richness by 25% above the current average. Moving forward, optimizing new dam sites to increase hydropower by 20%, rather than selecting the fewest number of dams, could reduce fish species losses by 89%. If decisions about locating new dams are combined with dam removal, then a win-win can even be achieved with 20% greater hydropower and 19% higher species richness. Regardless of hydropower targets and dam removal options, a key observation is that optimal sites for dams are mostly located in the upper reaches of the basin rather than along the main stem of the Sao Francisco River or its main tributaries.

中文翻译：

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优化巴西圣弗朗西斯科河流域的水电大坝位置和拆除，以平衡水电和河流生物多样性的权衡

摘要 为了支持发展中地区的生态友好型水电规划，我们提出了一种用于定位水坝的空间优化模型，以平衡水力发电和洄游鱼类物种丰富度之间的权衡。我们的模型包含两个特殊功能。首先，它是为热带洄游鱼类的扩散量身定制的，这些鱼类通常需要漫长、畅通无阻的河流才能完成它们的生命周期。为了模拟具有这种扩散模式的鱼类，我们引入了河流路径的概念，它代表了一种描述河流连通性的新方法。其次，它结合了关于大坝放置和拆除的决定，从而为水电抵消提供了机会。我们将我们的模型应用于巴西圣弗朗西斯科河流域，这是一个水电与淡水生物多样性冲突的地区。我们发现与大坝前基线相比，大坝使加权洄游鱼类丰富度降低了 51%。我们还发现，即使是有限的大坝拆除也有可能显着增强鱼类的生物多样性。通过新水坝的最佳选址来抵消单个水坝的拆除可以使鱼类丰富度比当前平均水平提高 25%。展望未来，优化新坝址以增加 20% 的水力发电，而不是选择最少数量的水坝，可以将鱼类物种损失减少 89%。如果将新水坝选址的决定与大坝拆除相结合，那么甚至可以实现双赢，水力发电量增加 20%，物种丰富度增加 19%。无论水电目标和大坝拆除方案如何，